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Instrumentation, Control, and Communications: On the Ground and In Flight
Multi-Modal Design, Manufacturing for Advanced Aerostructures
Dual-Side Dual-Chute Deployment for Reliable, Condition-Tolerant Recovery.
STAR's 2nd ever stage separation vehicle! Competing in IREC 2024 in the 30k COTS category
Kinetically Engineered Life Support Experiment - Yeast
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Bear Force One is STAR's first fiberglass airframe. This rocket will be flown in the IREC 2021 10,000 foot apogee competition.
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Our entry into the SDL Payload Challenge
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Block diagram showing all of the sensors and peripherals for each IRIS module in the 3 board stack
Pinout diagram for the stack connector, and interfaces to each Teensy 4.1 on the IRIS-Core modules. TBD
A diagram detailing the power flow architecture of IRIS
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You can find information on how to perform common tasks here.
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How to get started with software STAR uses.
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Sometimes we stop using things
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Tutorials that most people would probably need, and don't fit in a specific category
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Tutorials specific to the Airframe Subteam
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Similarly, launch lugs or rail guides
How to prevent the motor from falling out of the vehicle due to gravity or force from an ejection charge
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Current roster of Outreach Activites
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Tutorials for Operations
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Tutorials specific for the Propulsion Subteam
Looking for information on membership requirements, CalLink, elections, or more? Look no further.
Welcome to STAR's documentation! We are UC Berkeley's competitive rocketry team. You can find tutorials, intro projects, and more information here.
Still don't have edit access or can't access the STAR Internal space? Check out this tutorial.
This is a space for the general public, prospective members, and current members to access all sorts of documentation compiled by our team.
If you're interested in joining, we recommend starting with the FAQ and the Membership section, then moving on to the Intro Projects:
For current members and the general public, here are the major sections of our documentation. Tutorials are for the most part widely applicable to the sort of work we do, but many do pertain specifically to software or processes for STAR members:
Team-specific testing information and test forms can be found in the Testing section:
To contribute to our documentation, see the below page:
Documentation on specific current or past projects can be found at the STAR Internal space, which is restricted to members:
Compilation of important links and resources on the team! Also updated here: https://docs.google.com/spreadsheets/d/1QvLCy1SLycjZrwfG2lQjOvpugUm144z0Te77fRIiMmY/edit#gid=0
"Democracy is the road to socialism." - Karl Marx
While not a requirement, active members are invited to participate in subteam and general elections.
Rules are detailed in our constitution, which can be found at the link below--choose the most recent version. The constitution is the only authoritative source for rules concerning elections. That being said, election information will be generally outlined below for your convenience.
We are proud to say that all of our official technical and administrative leadership is elected!
Elections are usually run by the President and Vice President, although there is no constitutional requirement as to the body that must hold the elections or the manner in which they are to be carried out.
Generally (although again not codified), we strive to have elections follow these principles:
Free and Fair: only eligible members vote, and follow one-person-one-vote. All eligible votes are counted, and a reasonable effort is made to make sure any eligible member can vote if they desire. No eligible member is prevented from running for a position.
Confidential: use some form of secret / Australian ballot; you have a right to vote without others knowing your choice.
Transparent: the results and process should remain accountable and subject to re-count.
From the constitution,
Elections will occur towards the end of the spring semester but prior to the last day of the semester. The Executive Board will serve a year-long term starting after the final competition event, even if that competition event is held in summer.
This allows for relatively constant leadership for each project, or each school year in the event that a project lasts for multiple years.
This includes positions like the President, Vice President, Documentation Lead, Logistics Lead, and Business Lead. From the constitution,
Club-wide positions will be elected through a simple majority vote of all active members. If a simple majority has not voted for a single candidate, the two candidates who have received the most votes will enter a runoff election with simple majority vote. A person is allowed to vote if they have been an active member on the team for at least a semester prior to the election.
Subteam elections are a little more complicated, taking place in two phases: nomination and confirmation.
First, subteams nominate a candidate using a form of ranked-choice voting called Single Transferable Vote (STV):
The voters rank candidates in their order of preference on their ballots, including a “no confidence” vote indicating that they do not wish to transfer their vote to any subsequent candidates on the list
In each round of voting, the candidates with the fewest votes are eliminated. Each voter who voted for those candidates transfers their vote to the next candidate on their preference list, leading to the next round of voting with these new tallies
At the end of this process, the candidate with a majority of available votes wins the nomination.
Nomination votes usually take place during the normal subteam meeting time.
This Candidate Subteam Lead will then be confirmed through a simple majority vote of all active members. If a Candidate is rejected, the runner-up of the subteam election will be nominated as the new Candidate.
Usually, Subteam Leads confirmation votes for all subteams occur in a single GM during which the voting for club-wide positions also takes place.
Active membership is defined in the constitution explicitly, but you can generally take it to mean fulfillment of the . These elections usually happen during GM near the end of the year.
If you aren't interested in the math behind it, it suffices to say that voters rank their preferences and a winner is chosen that will satisfy people. (If you are interested in the math, check out !)
Website (meant for the public/PR purposes)
Gitbook (meant for members/showcase technical work)
Google Drive (where all the work happens)
GrabCAD (all the design work!)
Message your project manager to get invited
Github (all the code work!)
Youtube
Team Glossary
Trello
Message your project manager to get invited
Discord
message @arby#8576 for invite link
Compilation of all current projects that STAR is working on this academic year!
Team Development/Technology Capabilities
Rapid design iteration
Physics, Analysis-oriented testing
Efficient Cross-Specialty Collaboration
Development for Reliability, Robustness
Expand team technicality, individual learning capability
STAR's First Liquid-Powered Flight Vehicle
Ongoing membership requirements
Every member is expected to attend General Meetings; if you have a recurring conflict, you may be excused from this requirement. According to our constitution,
Failure to attend at least three-fourths of general and subteam meetings may result in loss of active member designation as stated in Article III.
Subteam leads will note attendance at GM and subteam meetings.
Every member is expected to participate in two hours of Outreach per year. Contact the Outreach & Marketing Lead for details; usually signups will be announced on Discord. These are extremely fun and rewarding opportunities to
Every member is expected to make one contribution to project documentation each semester. Contact your subteam documentation liaison for what this entails; contributions range from creating an entire tutorial to fixing minor errors in a GitBook page. Thanks for helping out!
Target Apogee, Precision: 2500m, +-10%
Approx. Vehicle Mass: 40kg dry
Approx. Thrust Level, Burn Time: 1.80kN, 10sec
Bi-Liquid LOX/Ethanol for Precise, Reliable Thrust
High-Level Rocket Structure: Thrust Range, Vehicle Mass (+-50%)
Conservative(High-Thrust) Thruster / Feed System Design + Review
Fluid System Assembly, Testing, Calibration. Instrumentation and Control Development. Flight Structure Design Integration
Static Fire Testing. Mass Optimization, Simulation Refinement.
Flight Vehicle Integration
Priorities: Stable, Conservative Perfomance and Efficient Manufacturing/Assembly
Injector: Unlike-Doublet Impinging, LOX-centered
Chamber: Ablative + Fuel Jetted Wall-Film. 6061 Aluminum Jacket.
Nozzle: Graphite Throat, 316L Stainless Steel Expansion
This is where all of the previous projects that STAR has worked on are listed!
We designed our fins based on the need of our rocket. Initially, we had fin dimensions that were larger. However, as our rocket design developed we realized that this design was not meeting our apogee and stability needs. Each change would need our fins to be altered which was constant. After our rocket design was set, we began our fin simulations with respect to our motor simulations. We wanted to make sure our fins and motor complimented each other. We did different fin-size simulations for each motor we felt could be used to meet the needs of our rocket. After many fin/motor simulations and utilizing the optimization tool in Open Rocket, we landed on our current fin dimensions.
Distance between root cord to tip cord (inches) - Numeric data only
7.4 in
Description of the method used for securing the fins to the airframe.
Sand areas of connection before applying epoxy. Clean off any fiberglass dust with IPA solution. Spread epoxy(JBweld) all around the bottom of the fin tab and side of fiberglass, so that it is completely coated.
Use the fin jigs to place the fins into the fin slots on the booster tube, so that the tabs are touching the motor tube and the aft side of the tab is touching the middle centering ring.
Create smooth epoxy fin fillets around each fin. After thoroughly mixing, wear gloves and use your finger to apply a generous amount of epoxy at the seams between the fins and the booster tube.
Once all three fins are cured and attached, align the aft centering ring with the rest of the rings, but do not epoxy it in. Keep multiple zip ties wrapped around the ring so that once it is perfectly aligned, it can be pulled out.
Epoxy the aft centering ring into the exact position established in the previous step. If it falls out of alignment, use one of the extra aft centering rings and try again, until it is successful. Allow the epoxy to cure for 24 hours.
This step will also take place after fin glassing and after the aft rail button is attached.
Final details
Fin glassing
General Procedure:
Roughen surface with 80 grit sandpaper.
Clean surface with 50% IPA, 50% water.
Cut 3 types of cuts of cloth:
First cut of cloth goes over the fillets, goes less than a third of the way up the fin, need 6 of these.
Second cut goes up ~⅔ of fin, and out to the midpoint between the fins on the airframe, need 6 of these.
Third cut goes from tip of one fin to tip of the adjacent fin, need 3 of these.
Mix epoxy in ratio given on instructions. Need a 3:1 ratio between epoxy and cloth.
Application:
Wet surface with epoxy.
Put a cloth layer on top of epoxy; it will soak the epoxy into itself.
Squeegee the excess epoxy and bubbles out of the layup to make it smooth.
Once all three layers are on, apply peel-ply over the layup.
Cure vertically.
Vacuum bag the entire fin area to ensure a smooth cured surface. Apply breather cloth to the peel-ply before bagging.
Once cured, sand down composite surface.
Please describe the method and results used to determine the not to exceed flutter velocity or the divergence velocity.
We used the flutter boundary location to determine the rocket’s flutter velocity and ensure that our rocket’s velocity never exceeds this flutter velocity. Assuming our maximum altitude, which is the apogee of 10,000 feet, we were able to derive the estimated air temperature and estimated speed of sound. Finally, we were able to apply our fin geometry to calculate the fin flutter velocity, which is 1682.16 ft/s (1146.9 mph). We confirmed this value using the software FinSim, which combines our fin geometry with more specific rocket data to calculate this same value. Since our rocket’s maximum velocity is predicted to be 972 ft/s, we will not exceed flutter velocity.
All vehicle, electronics, and recovery (pounds) - Numeric data only: NOT including motor case, propellant, or payload weight
48.897 lb
0.503 lb
11.7 lb
Must be at least 8.8 lbs per IREC Rules (pounds) - Numeric data only
9.5 lb
Vehicle weight + propellant weight + motor case/structure + payload weight (pounds) - Numeric data only
70.6 lb
The location of the center of pressure measured in inches from the tip of the nose cone. Numeric data only.
91.426 in
The location of the center of gravity measured in inches from the tip of the nose cone. Numeric data only.
79.264 in
The distance between the CG and the CP at lift-off is divided by the airframe diameter, measured in calibers. 1.5 is the highly recommended minimum
1.97 cal
Discuss each airframe joint, including couplers, shoulders, and attachment method(s).
Ref. DTEG 8.5 - Airframe joints that implement “coupling tubes” should be designed such that the coupling tube extends no less than one body tube caliber on either side of the joint – measured from the separation plane. The nose cone is epoxied onto the payload tube. Airbrake coupler attached to airbrakes tube with epoxy. Booster tube coupler is attached to the airbrake tube with #6-32 black-oxide alloy steel screws and to the booster tube with epoxy. Av Bay coupler attached to the main parachute tube with epoxy.
#4-40 nylon screws placed between payload tube and Av Bay coupler.
#4-40 nylon screws placed between Av bay tube and main parachute tube.
Discussing the construction of your rocket including airframe, couplers, interstage couplers, nose cone, fins, fin attachment, composite materials, and identify commercial or SRAD components.
https://docs.google.com/document/d/1KZSKXfp3WzLMbTYALbvnvTjxdE30VmkWheWptSs8Wp4/edit?usp=sharing
https://docs.google.com/document/d/1zdzwSvZdx3QNCro2Ow7lJZkjrqIrI5-QjmlmlRy3plg/edit?usp=sharing
https://docs.google.com/document/d/11EJxgDgyR533UyZEACwQ8Kov9MOq7I9INR4dPBZpjkk/edit?usp=sharing
https://docs.google.com/document/d/123OBOUEgaW2C-NUJAULUbGjeWIXQ4C2dBecxAn0cElw/edit?usp=sharing
Solid
Propulsion Manufacturer *
Aerotech
Aerotech M1939 W-P
M
1,939.0 N - Avg thrust given by thrustcurve.org/motors/AeroTech/M1939W/
2,429.7 N - Max thrust given by thrustcurve.org/motors/AeroTech/M1939W/
10,481.5 Ns - Total Impulse given by thrustcurve.org/motors/AeroTech/M1939W/
10,369 Ns - Total impulse given by RASP simulator file from thrustcurve.org/motors/AeroTech/M1939W/ ** explanation given in propulsion narrative and additional comments.
Numeric data only (Seconds)
6.52 s - Motor burn time given by Open Rocket
6.2 s - Motor burn time given by thrustcurve.org/motors/AeroTech/M1939W/
Due to judges comments from our previous reports, we redid our propulsion simulations through OpenRocket. We used the RASP format simulator file from Thrustcurve.org. However, we wanted to preface a discrepancy between this file and the given information on the Thrustcurve site. For our motor, Aerotech M1939-W the written total impulse is given as 10481.5 Ns. However, the total impulse in the RASP file is 10369 Ns. All our simulations were done with this file, therefore using the impulse value of 10369 Ns.
Experimental Liquid Low Impulse Experiment
STAR's first generation liquid rocket engine
The Experimental Liquid Low Inpulse Engine (ELLIE) is the first time that STAR has attempted to create a bi-propellant rocket engine. Its purpose was to lay the groundwork for a flyable liquid in future iterations.
The team is required to stay in the bunker during a hot fire, so the engine must be controlled remotely. We chose to use two ESP32s, one of which would send commands (COM Board
), and the other would report data (DAQ Board
). Both devices were constructed as state machines, with COM Board connected to the computer to transmit the data reported by the DAQ Board.
Here is a state machine diagram to visualize the communication:
Since the bunkers and the launch pad are approximately 100 ft apart, using a wired cable between the ESP32s, although reliable and still popular in collegiate teams, was not economically efficient. Instead, we established a wireless connection between the COM and DAQ boards, with an information queue that can hold data while transmitting.
The "pts" are the pressure transducers we implemented throughout the engine system, while the "lcs" are load cells for measuring the engine thrust, and fm is the flow meter measurement. For both sending and receiving data, functions and interrupts are set up to handle.
Establishing the data structure for communications:
In setup()
, we need to call the following commands to get everything working:
The following code is the implementation of the state machine. State cases such as -1, 30, etc. are omited since they are only for testing and debugging purposes. Those states are not a part of the main hot-fire sequence.
Gasesous Oxygen - Liquid Ethanol (95%) Rocket Engine
Thruster:
Radiatively Cooled (Heat Sink) Combustion Chamber / Nozzle
Injector: Coaxial Shear element mixes compressible GOX with ethanol. Dampens pressure instability through 30% Combustion Pressure element flow resistance
Thrust Measurement: (Target 30lb thrust)
Three S-type load cells, together, measure total thrust force
Pressure Measurement:
Wheatsone Bridge Diaphram Pressure Transducers measure intense distributed forces
Feed System:
Energy Regulation:
Spring-Loaded Regulators and Stainless Steel Ball 2/3-way Valves.
High-Pressure copper tubing, braided stainless steel flex hoses.
STAR's First Minimum Diameter experimental rocket (Launched December 2022)
MINDI achieved an apogee of 14,325ft, which was the highest apogee reached by any UC Berkeley team at the time.
Data Analysis, Future System Uses
A valuable lesson we learned from the previous hot-fire experience is that we cannot rely solely on commercial piping components, such as off-the-shelf valve regulators, to control the engine system accurately. Therefore, the ELLIE team is continuing as a long-term research group, focusing on advanced valve control.
A significant concern has been the droop in the system. It has severely impacted our engine performance, since only a fraction of the GOX flow truly occurred, which resulted in a fuel-rich burn. Here is the visualization of the issues caused by droop, plotted in MATLAB:
PT1 measures the pressure of the combustion chamber downstream, while PT2 measures the pressure of the GOX flow. It appears that the GOX regulator's droop was much higher than what we expected, since we have addressed droop by intentionally setting the regulated pressure higher than the nominal pressure. The result was a low-pressure, low-mass flow burn in the combustion chamber. This conclusion is supported by PT1 data with a high point of about 150 psi, which is 100 psi below the GOX pressure.
The ELLIE team is addressing this issue by designing a self-regulated valve. The valve will be able to adjust the flow rate according to real-time pressure changes to guarantee a desired mass flow rate.
Data Analysis (Refer to P&ID on Physical System for instrument locations):
Data:
Max Thrust: ~32 lbf
Combustion Chamber Pressure: ~145psi
Upstream GOX Pressure: 250psi
Upstream ETH Pressure: 335psi
Analysis:
Thrust was ~1/3 predicted:
GOX feed pressure was very low > sustained a low-pressure reaction in chamber
Low Combustion Chamber Pressure + low flowrates > low combustion chamber pressure.
Long-Term ELLIE system goals:
Use existing printed circuit board and fluid system for component testing of LE2
Build upon fluid system to test active flow control valves for LE3
UC Berkeley's first student-built staged rocket
PinkBeary (SSEP) was launched at FAR on 17 September 2022. The mission of stage separation was successful, but a rapid unscheduled disassembly (RUD) about 1 second after upper stage motor airstart due to improper airframe connection caused a partial mission failure.
The project originated from "Hot Take," a project proposal that outlined a plan for STAR to explore liquid rocketry.
During this phase, the team mainly focused on designing the physical system, as well as manufacturing various parts of the liquid engine, such as the injector and combustion chamber.
Most of the software and electrical development occurred during this phase.
The first attempt did not succeed, but it provided valuable information regarding the flaw in our system.
Successful hot-fire with a burn time of 6 seconds.
New altimeter wiring will involve short lengths of wire soldered directly into the altimeter at one end and into a crimp connection at the other.
One of the recovery subteam’s slowest steps at launch is connecting wires to the altimeters. The spaces that the wires must be fit into are very small, making it difficult to maneuver and secure them. This can lead to delays because connecting the wires is time-consuming and insecure connections can lead to ground test failure. It also cannot be fully-completed ahead of time as the altimeters must be re-wired between ground test and launch.
Previous solutions have involved positioning the altimeters on the sled such that the connections are easier to access and using crimps to speed up the connection process. However, even with good altimeter placement, it can be difficult to position the wires. Recovery also had issues in creating secure connections to the crimps and did not consider them reliable enough for launch.
Recovery plans to solder short lengths of wire directly into the altimeters at one end and into a crimp at the other. The end with the crimp could then be easily connected to a longer wire for ground test or flight, saving time at launch. Soldering into the crimp should increase the security of the connection, preventing the previous problems associated with crimps.
This solution allows recovery to change the wiring of the altimeters, despite soldering a wire permanently into the altimeter because the long wire going to the other connection point is replaceable. Solutions involving solder were previously not considered because of the requirement of reconfiguring wires at launch.
Deciding the diameter of this rocket was a very important task. We wanted this rocket to be cost affective and aerodynamic, but also versatile.
The total cost for a 5.5 inch diameter rocket is $680.57.
The total cost for a 6 inch diameter rocket is $867.05.
We decided that a 5.5 inch diameter rocket would be most beneficial. While this option is not the least expensive, it does allow for future growth. Although a 5.5 inch diameter rocket reaches a lower apogee than a 6 inch rocket and can carry less payload, we decided it is more beneficial for us as a club to understand the process of building and launching a dual stage rocket than it is to overdo our first attempt. A 5.5 inch stage separation rocket is not too risky, but will also allow us to use larger motors and reach higher altitudes in future launches. This rocket will help us gain experience in designing, manufacturing, and launching a dual stage rocket. This will be beneficial overall for the club and our long term goal of achieving a space shot.
See these two documents for our original data and cost comparisons, plus sources and links to purchase the parts.
Item | Unit Cost | Quantity | Total Cost |
5.5" 4:1 Ogive Nosecone | $37.95 | 1 | $37.95 |
5.5" x 48" Blue Tube | $56.95 | 3 | $170.85 |
5.5" x 48" Full Length Coupler | $55.95 | 2 | $111.90 |
75mm x 34" Motor Mount Tube | $16 | 1 | $16 |
54mm x 34" Motor Mount Tube | $9.78 | 1 | $9.78 |
Aero Pack 75mm Motor Retainer | $56.67 | 1 | $56.67 |
Aero Pack 54mm Motor Retainer | $34.44 | 1 | $34.44 |
J315R Motor | $84.99 | 1 | $84.99 |
K1000T Motor | $157.99 | 1 | $157.99 |
Item | Unit Cost | Quantity | Total Cost |
6" 5:1 Ogive Nosecone | $94.95 | 1 | $94.95 |
6" x 48" Blue Tube | $66.96 | 3 | $200.88 |
6" x 48" Full Length Coupler | $66.95 | 2 | $133.90 |
75mm x 34" Motor Mount Tube | $16 | 1 | $16 |
Aero Pack 75mm Motor Retainer | $56.67 | 2 | $113.34 |
K535W Motor | $149.99 | 1 | $149.99 |
K1000T Motor | $157.99 | 1 | $157.99 |
How the fins geometries were determined
Material Choice: Fiberglass (Balsa wood too weak given geometry and speed)
Geometry Options
Best Performance: Triangular
Root chord: 8 in.
Tip chord: 0 in.
Height: 5.5 in.
Max rocket speed is 92% max fin flutter speed
Highest apogee: 8460 ft.
Best Choice: Trapezoidal
Root chord: 8 in.
Tip chord: 3 in.
Height: 5.2 in.
Max rocket speed is 65% max fin flutter speed
Highest apogee: 8344 ft.
Viable: Elliptical
Root chord: 8 in.
Height: 5.2 in.
Highest apogee: 8282 ft - consistently outperformed by trapezoidal fins with comparable stability, geometry
Thickness Choice: 1/8” (Thinnest option that could withstand max speeds)
Stability
Ranges from 1.31 - 1.5 on design view
Consideration of high speeds shift this stability to around 1.8-1.9 according to simulations, so this meets the recommended requirements
For lower stage fins, a range of 1.5 - 2.5 should be used, which of course means a change of geometry
Decided on trapezoidal over elliptical based on OpenRocket data
Increased thickness of both sets of fins to 3/16” based on FinSim data because FinSim accounts for fin divergence also
Adjusted the geometries based on the most recent (version 2.0.1) ork to work with stability margins and updated to version 2.0.2 (All ork versions)
Upper Stage
Root Chord: 8”
Tip Chord: 3”
Height: 5.5”
Stability: 1.27 cal
Lower Stage
Root Chord: 10”
Tip Chord: 3.5”
Height: 5.7”
Stability: 2.19 cal
Spreadsheet - Used for fin flutter calculations
Description and instructions for understanding and implementing your own calculations for Pyro Bolts used in Stage Separation.
Pyro Bolts are an effective way of performing stage separation for in flight vehicles and they can be carried out in a number of ways. Our design prides itself on simplicity, cost effectiveness, and reusability (except for the bolts themselves).
We start with two manufactured O-rings that are each epoxied (or fastened otherwise) to our two airframe tubes, these rings will stay attached throughout the entire launch-recovery process. We then take screws and drill them out, fill them with black powder, insert igniters (e-matches, insert 2 for redundancy), then seal the fasteners. This process is detailed in separate sources and in our stage separation testing documents. The screws can be inserted through holes in the both the O-rings and will be fastened with a wing nut located on the other side of the opposite O-ring. When all screws are ignited, they ideally break and there is no longer anything keeping the two stages together. To ensure separation we opt to place springs between the O-rings, around the screws in order to add force for separation. We can then epoxy multiple standoffs between the rings, to ensure all heights and alignments are correct.
It is extremely important to perform calculations before all else, both to make sure your design is feasible and so that you can select and reference what parts/materials you are planning to use. The specific calculations will vary for each design, but the quickest way to think about what calculations are needed are to think about the forces placed on each part and on all surfaces that connect parts together. We should also check the calculations for the events that take place (black powder and spring actions). For our design above, our main concerns are:
Can the black powder we have break the screws?
This is dependent on several factors, mainly:
mass of BP (depends on volume of drilled hole)
shear strength of screw material (accounting for the drilled out hole as well)
Will the screws be able to handle the stress of launch?
Dependent on:
stress strength of screws
this depends on the material and surface area of your screw so account for the fact that the screws have been drilled out a bit
stress strength of nuts
Do the springs fall within the right window of strength (given a reasonable compressed height)?
Depends on
Spring strength
Height between Rings
Friction needed to overcome (you can estimate this, we chose 5 lbf)
Make sure you fall within the window, the spring should be strong enough to help separate, but not so strong that it causes unnecessary stress on the O-rings and screws.
Is the epoxy strong enough to hold the O-rings and the airframe tubes together during launch?
It probably is but it's best to check, depends on:
Surface area between O-rings and Airframe tubes
Strength of epoxy
Mass in upper and lower stage
Acceleration of rocket during launch
These are some of the important calculations needed, however the more you can think of, the better. Make sure each calculation gives us a reasonable factor of safety (use your good judgement).
Electronics used for SSEP
This altimeter will be used in both the upper stage main and drogue parachute deployment.
Purpose (Upper Stage Main): Dual Side, Dual Deploy Entails: Pyro leads to main and drogue (redundant), deployment based on elevation and velocity.
Purpose (Lower Stage Main): Single Side, Single Deploy Entails: Pyro leads to main (redundant), deployment based on elevation and velocity.
Specs:
Works to 100,000 feet MSL, audibly reports peak altitude and maximum velocity after flight.
Stores 16 flights of 18 minutes each (altitude, temperature, and battery voltage at 20 samples per second) for download to a computer with the optional DT4U USB interface. Hi-speed sampling and storage of battery voltage serves as a useful aid in diagnosing intermittent problems with your battery, switch, and wiring. All data are preserved with power off.
Deploys drogue and main chutes with audible ematch continuity check.
Outputs capable of 5A current for 1 full second to allow use with nearly any ematch or ematch substitute. Reverse polarity protection prevents spontaneous firing if battery is connected backwards.
Main chute deployment altitude is adjustable from 100 feet to 9,999 feet in 1 foot increments. 9 presets allow for quick change in the field.
No mach delay necessary for mach+ flights: Automatic MachLock assures proper operation with any flight.
Brownout protection will tolerate 2 second power loss in flight – no need for multiple batteries.
Precision sensor & 24 bit ADC yield superb 0.1% accuracy.
Built-in voltmeter reports battery voltage on powerup – no more guessing about battery condition.
Post flight locator siren aids in locating your rocket.
Confusion-free individual terminal blocks – unreliable multiple wires per terminal are not necessary. Dedicated switch terminal block eliminates the need for splicing switch into battery wire.
Highly resistant to false trigger from wind gusts; tested in 100+ MPH winds!
Selectable apogee delay for dual altimeter setups prevents overpressure from simultaneous charge firing.
Low power design runs for weeks on a standard 9V alkaline battery. Post-flight locator siren will run for months, giving you multiple “second chances” to find a lost rocket.
Telemetry output for real-time data in flight with your RF link.
Rugged SMD construction, stringent QC testing, and internal self-diagnostics assure uncompromising reliability.
Wide operating temperature range of -40F to +185F.
Measures just 2.0"L x 0.84"W x 0.5"H, fits 24mm tube, weighs just 0.38 oz.
Manual: http://www.perfectflite.com/Downloads/StratoLoggerCF%20manual.pdf
The Altus unit comes at a hefty cost, but has the advantage of being able to provide angle caculations. using two different altimeters for the same deployment is not advised since it would require two different switches.
Purpose: Lower Stage Parachutes (Drogue and Main, DSDD), Separation Mechanism Entails: 3 additional programmable pyro events for separation mechanism (redundant).
Specs:
2.25 x 1.25 inch board designed to fit inside 38mm airframe coupler tube
Supports dual deployment and 4 additional pyro events.
Pyro events are configurable and can be based on time and various flight events and status, including angle from vertical (for safety in staging and air start flights).
Barometric pressure sensor good to 100k feet MSL
1-axis 105-g accelerometer for motor characterization
3-axis 16-g accelerometer for gyro calibration
3-axis 2000 deg/sec gyros
3-axis magnetic sensor
On-board non-volatile memory for flight data storage
USB for power, configuration, and data recovery
Integrated support for LiPo rechargeable batteries
User choice of pyro battery configuration, can use primary LiPo or any customer-chosen separate pyro battery up to 12 volts nominal.
IMPORTANT! Easy Megas must be wired BACKWARDS (i.e. a custom JST connector must be assembled to plug the negative battery terminal into the "positive" end and vice versa) due to manufacturer decision.
Manual: https://altusmetrum.org/AltOS/doc/altusmetrum.pdf
Purpose: Airstart (Motor Ignition)
Entails: Single lead to motor ignitor
Specs:
66mm x 25mm, weight ~12 grams
Dual-ended output - pyro igniter is dead until near deployment for safety
Records altitude up to 60,000 AGL
Drogue programmable 0-3 seconds after noseover, main programmable from 100-2000 feet
Wifi compatible - arm via phone
Polarity-independent
Comes in a kit - must be soldered and assembled
General page including external interfacing documentation.
The Common Avionics System (CAS) is a system for Avionics hardware development with the primary motives being to reduce hardware development time by better leveraging existing verified designs. CAS achieves this by splitting functionality into separate modules. This allows each module to do one thing and do it well, without having to redo aspects of the system that have already been done. CAS will allow Avionics to more easily support new projects and will reduce risk (in the long-term) by reusing well-tested designs.
Stack: A set of modules placed vertically with standoffs separating them.
Module: A single printed circuit board (.062" thickness) that has the hardware to satisfy a certain function.
See image below for cross-section of a stack (specifically of a module). The modules are square PCBs with 4 mounting holes in the corners (large filled yellow circles with blue-green halo). The arrays of smaller empty yellow holes are header pins for connection to other modules in the stack.
The side to side distances are 2.5 inches and mounting hole to mounting hole distances are 2.2 inches. The space from the top of a module to the bottom of another module is 0.6 inches.
The types of pins that appear on the bus are:
Power
+3.3V
+5V
+BATTERY
GND
I2C0
SCL
SDA
I2C1
SCL
SDA
SPI High-Speed
SCK
MISO
MOSI
SS1, SS2
SPI0
SCK
MISO
MOSI
SS1, SS2, SS3, SS4, SS5, SS6, SS7, SS8
Interrupt pins
INT1, INT2, INT3, INT4, INT5, INT6, INT7, INT8
The entire CAS stack's voltage rails (3.3V and 5V) are powered by a power management unit located on the core board. This power unit on the core board recieves +7.3V DC from an external battery. The entire CAS stack generally draws below 50 mA of current when not doing power-intensive tasks.
To separate modules from each other, use a flat-head screwdriver as a lever, as shown in this picture:
Common Avionics System bringup and flight validation. This project was cancelled in 2022.
CAS Board standards document (describes how to develop modules for CAS):
All of the modules in CAS share a common 80-pin bus. Not all of the pins have functions assigned yet, but they may be assigned in future modules. The CAS modules must never conflict with the common bus pin-to-function assignments. The pin-to-function mapping is recorded in this google sheet:
Communication with Ground Station, and also a GPS chip
The Radio module contains an RFM69 radio transciever module (with an attached antenna) whose purpose is to transmit data from the rocket to the ground station in real time. The radio module also contains a SAM_M8Q u-blox GNSS chip which can determine time, latitude, longitude, and altitude. The micocontroller can communicate with the radio through the SPI0 bus, and communicate with the GNSS chip over the I2C1 bus. There are also a couple of optional extra I/O interface pins on the GNSS module that can be connected to external jumper wires.
The radio's output can be sent either to the antenna or to an SMA cable (for testing what data is sent). There are two jumper pins on the board, JP1 and JP2, which control which of the two destinations is connected to the radio's output. JP1 can be used to manually set the radio's output between to the antenna or to the SMA. JP2 can be used to override the selection on JP1 and have the selection be made by the Microcontroller instead. Note that JP1 is on the top of the board and JP2 is on the underside.
The current version of the radio board also has one extra connection made with a white soldered-on wire, which connects the DIO0 pin on the radio transciever to the A20 pin of the CAS Bus (INT 8). This could be used in the future to program the radio transciever to send an interrupt over the DIO0 pin which would reach the Microcontroller at interrupt pin 8.
Normally, the radio should be operated at either 915 MHz or 433 MHz.
The power, CPU, and other essential functions
The Core Module contains the main MCU (an STM32F401RE chip), three sensors (BMP388 altimeter, BNO055 IMU, MAX17049 fuel gauge), an SD card holder for data logging, a UART debugging port, and USB and JTAG connectors. It also provides power for the other modules through the CAS Bus 5V and 3.3V power rails.
The STM32 microcontroller connects to an I2C bus (numbered I2C3) that does not connect to the CAS Bus, bus instead conencts only to the three sensors on the core board itself. The microcontroller also connects to an SPI bus (numbered SPI3) that does not connect to the CAS bus, but instead connects to the SD card holder and the SPI-to-I2C translator. Lastly, note that the I2C2 bus on the CAS bus does not connect directly to the microcontroller, but instead goes to the SPI-to-I2C translator.
The core board also features a "user button" and "user LED" for testing purposes. There is also a RESET button, but this button does not do anything unless there are jumper pins attached to the RESET jumper.
At the time of this writing, none of the three sensors have been soldered onto the board yet because we have been unable to buy them so far (except for the BMP388, which we bought recently but haven't soldered on yet).
For testing, assemble the module and plugin a battery supplying 7.3V.
Test bus power sources. Make sure the voltage of all power pins match the specification.
Check USB. Connect USB to the computer and see if the flasher can recognize it.
Run echo and LED test. See if we can flash the chip through the debugger, then check if the user LED is blinking and if the UART outputting the correct message.
Run sensor connectivity tests for all onboard sensors. This includes checking if we can read the ID registers of IMU, Altimeter and fuel gauge.
Verify the functionality of onboard sensors. Read actual data from the sensors and see if they match expected values.
Test bus interrupt pin connections. Connect a jumper from the 3V3 power pin to an interrupt pin and see if we read the correct value. Repeat this for GND and every pin.
Check SD card IO. Check if we are able to write data and read back from it.
Sensors and Actuators to drive the propulsion system
The prop module is currently still in development. The prop module is unique in that it consists of three boards, not one, since the components would not all fit on one board. Also, the prop module requires a separate power supply connector because one of the components (a solenoid) requires a +24V power input, which is greater than the battery can supply.
The current plan for the prop board will include connectors that attach to several sensors and actuators used in the propulsion system. These sensors and actuators are not on the boards themselves, but are instead wired to the connectors on the edges of the boards.
The main specifications for this module are:
5 Pressure Transducers
3 Load Cells
3 Thermocouples
3 Servos
2 Solenoids (to open valves)
Oxygen Flow Meter (Not yet decided if we should include this)
Eight fuses that can light blackpowder charges
The pyro module consists of eight connectors which can each light a blackpowder charge. Each connector is controlled by a mosfet, and if the mosfet allows current to flow through the connector, then the blackpowder charge is ignited.
The core module controls this by sending I2C messages over the I2C0 bus to the I/O expander module. The I/O expander module connects to eight mosfet drivers which drive the mosfets. The I2C messages that come to the I/O expander can tell it to set off certain blackpowder fuses.
The I/O expander also features three address bit jumpers, which can be manually connected or disconnected to change the I2C address of the I/O expander, to avoid I2C address conflicts.
Core module powered by a raspberry pi and an FPGA
The core-revised board is still in development. The plan for this board is to use a raspberry pi compute module 4 ("rpi CM4") as the microcontroller for the board. The board will also have an ICE40 FPGA that serves as an I/O expander, since the rpi CM4 has a limited GPIO pin count.
The specification for this board includes the following components:
rpi CM4 microcontroller
ICE40 FPGA
2 camera connectors
2 HDIMI connectors
An SD card slot
A microUSB port (with an ESD protector)
3 sensors (the same as on the original core board)
a PCIe connector (we still haven't fully decided if this should be added or not)
The rpi CM4 has 45 GPIO pins that can be mapped to various functions. See pages 8 and 9 of the rpi CM4 datasheet (https://datasheets.raspberrypi.com/cm4/cm4-datasheet.pdf) for the full list of possible pin assignments. See the "GPIO to CAS Module" google doc (https://docs.google.com/spreadsheets/d/1WoIMGLvNKh1mcGZh1nwG_u1I8tszVKkk_6aB_qJbBj4/edit?usp=sharing) for the list of pin assignments that we decided to implement.
Note that GPIO0 and GPIO1 have three functions--they can be used as either SMA pins to connect to the FPGA, or as GPIO pins to connect to one of the camera connectors, and on top of that, both pins are also used as UART debugging pins.
The rpi CM4 will use the "secondary memory interface (SMI)" to communicate with the FPGA through the pins that have been assigned SMI functionality.
This schematic describes the overall plan for the entire module, which shows how each of the components should communicate:
This core module is largely inspired by the design from the rpi CM4 I/O board, which features many of the same components (HDMI, PCIe, camera connectors, etc) also connected to an rpi CM4. The I/O board design is located here: https://datasheets.raspberrypi.com/cm4io/CM4IO-KiCAD.zip
The symbol and footprint for the rpi cm4 are located here: https://github.com/Kedarius/RPi-CM4-Kicad
Radio module with a powerful AT86RF215 transceiver
The radio-revised board is still in development. The plan for this board is to use an AT86RF215 module as the radio transciever, which can transcieve over two channels independently at different frequencies.The core board will communicate with the AT86RF215 through LVDS signals, which are output by the FPGA on the core-revised board and travel over LVDS pins on the cas-bus.
Most of the design for this module is directly copied from the cariboulite radio board design (which also uses an AT86RF215) here: https://github.com/cariboulabs/cariboulite/blob/main/hardware/rev2/schematics/CaribouLite.PDF
DAVE: Deployable Aerial Vehicle Experiment or DAVE Aerial Vehicle Experiment. Project initiated Spring 2020. The project was cancelled in August 2023.
Heck no! There are other places to do that.
Payloads such as the muon detector benefit from extended time in the air. Other potential payloads may benefit from a more gentle descent, or placement in a specific location. Additionally, DAVE-specific payloads may be interesting, such as aerial mapping, rocket-spotting, etc.
Getting a conventional UAS to this altitude can actually be quite difficult at this scale. While it is certainly doable, there may be applications for this sort of vehicle in a situation where rapid response and having a presence at these altitudes is important. The autonomous functionality is critical in these scenarios. For example, while fighting a fire, being able to quickly get a picture from the sky may be useful for firefighters on the ground.
Write it down on the Trello card and message in #payload-dave! Even if we are actively focusing on IREC payloads, we can always be writing down good and interesting ideas.
Intercollegiate Rocket Engineering Competition, 2020 and 2021
Welcome to the IREC 2020 & 2021 Projects page! You can find both technical and non-technical information about our 2020 and 2021 project here.
Kept everything pretty simple, mainly to get new members familiar with our current systems and have a reliable project for competition
Primary changes to Airbears designs include improved wiring and accommodations for fiberglass tubing. This project also is significantly heavier, has twice the target apogee (10k ft), and has a much larger diameter (6") than Airbears.
(With extremely scientific qualitative examples.)
DAVE deploys just after apogee, or the apex of the rocket's flight. In doing so, it uses its ejection mechanism to leave the payload bay in the launch vehicle's interior and pursue its own free-fall path to the ground. Doing so allows DAVE and its cargo to undertake a longer, more controlled flight separate from the parachute and the rocket fuselage.
Due to DAVE's full flight structure needing to be contained within a 6" diameter tube, the glider must be collapsable. In particular, both its primary wings (of Rogollo type) and its elevators must be collapsable in some fashion.
Additionally, the manipulation of our weight, lift, and drag force vectors are essential to DAVE having a controllable flight. DAVE currently has no mode for producing thrust, but a thrust-producing cargo may be pursued in the future. Calculations to determine the correct geometries (including wing sizing and placement) are located on the DAVE Trello board under Aerostructures.
As we would like to be able to control DAVE's flight from the ground, we will need on-board avionics. These avionics will control two types of control surfaces on DAVE: elevators and rudders. The elevators give DAVE control in the roll and pitch directions, while the rudders give the glider yaw control. Both of these will be located at the rear end of the vehicle - the Rogollo wings will be fixed and uncontrolled.
The grand purpose of DAVE is to carry onboard experiments that benefit from its unique deployment and flight pattern. Although the current designs for cargo carrying are not set, a goal is to have a modular interface, so any cargo concept that matches can go aboard.
This page will explain how to fold the parachutes and how to set up the related equipment.
Harness Components
Quick Links- metal rings that connect the shock cord to the u-bolts and also connect the parachutes to the shock cord.
Shock Cord- durable kevlar rope that holds all of the rocket together when parachutes are deployed.
Bulkheads- metal cylinders that are important for structural integrity. The u-bolts thread through the bulkheads.
U-Bolts- Are connected to the shock chord by a quick link.
Swivel?
Fold the Parachutes (Ideally a two person job)
Dedicate a 10 by 10 foot area to fold the main chute.
Lay out the parachute on its side and gather the shroud lines (the string coming from the edge of the parachute). This means that if the parachute was fully open with the inside facing up and you were standing at the center of the parachute holding all the shroud lines, that you move to the side folding it in half.
Make sure the shroud lines are untangled.
Examine each section and patch holes
Examine each colored section and patch holes.
For each section on one half of the parachute, fold the colored section in half do the edges of each section meet.
Have the folded half of the parachute on one side and the unfolded half of the parachute other on the other side.
Before continuing, only two sections of the parachute should be visible, with half of it folded under one color and the other half unfolded under the other color.
Fold the edge of the unfolded half of parachute to the middle and the the other edge to the newly created edge.
From the resulting rectangle, bundle the short edge four times until you have a resulting almost square parachute.
If confused watch the video attached.
The goals of the redesign of the avionics sled for the IREC 2020 rocket were the following:
Optimize the avionics bay for a 6" rocket
Address wiring concerns from AirBears to improve ease-of-use during launch
The new chosen design was an I-beam model, in which the batteries were placed in a center section of the sled and one altimeter was mounted to each side, as shown below. This design somewhat improved the space usage in the vertical direction, but there was significant unused horizontal space. The Recovery subteam selected this design because they felt it was more important to be able to wire the altimeters efficiently at launch than to use the least possible space.
Avionics Sled as viewed from back. Batteries are placed in middle centrals and the second altimeter is in the corresponding position on the other side of the sled.
Detailed description of the avionics bay and it's components. Useful for newer members to understand how the avionics bay works and the purpose of each component.
Many systems within a rocket are controlled by electronics, such as the parachute deployment systems, the motor ignition systems, and with our latest SSEP project, the stage separation mechanisms. These electronic controls are known as avionics, and they are essential to the function of the rocket, but they can be quite delicate and must be in proximity to the systems they are controlling so they can be wired effectively. The avionics bay houses these avionics in a relatively central location in the rocket and in such a way that the avionics are kept safe throughout the rocket's flight.
We use two main types of avionics bays: axial designs and radial designs. These names refer to how each design is installed into the rocket. Axial av-bays are inserted through the airframe tube along the tube's long axis, and radial av-bays are inserted radially through the side of the airframe tube, through a door in the tube. All radial av-bays have a sled, which houses the avionics and is the actual component to slide in and out of the airframe tube. Some axial av-bays have a sled design so that the avionics can be accessed radially as well, but this is not the case for all axial av-bays.
Full avionics bay for Bear Force One with the radially installed sled highlighted in blue (Right), and sled from avionics bay for Bear Force One with altimeters to control the parachute deployment (Left):
There are two main types of components discussed here: structural components and electronic components. The structural components serve to house the avionics (the sled) and to connect the inner structure to the rocket’s frame (bulkheads, u-bolts, etc.). The electronic components are the avionics themselves, notably the altimeters and CAS, along with their power supplies.
The following outer structural components are found in practically every av-bay, no matter the design:
Bulkheads: These usually metal plates connect the rest of the avionics bay assembly to the frame of the rocket.
U-bolts: These u-shaped bolts are fastened to bulkheads and connect the bulkhead, and therefore the avionics bay assembly, to a parachute assembly. Typically there is a fore u-bolt that connects to the drogue chute assembly forward of the av-bay and an aft u-bolt that connects to the main chute assembly aft of the av-bay. However, if there is only one chute assembly connected to the av-bay, as is the case with the lower stage of the SSEP rocket, only one u-bolt is needed.
Av-bay rods: These rods provide additional structural support for the av-bay and are fastened with wingnuts. They can be seen in the av-bay for Bear Force One as the two vertical rods, shown at the bottom of this section.
Bulkhead + u-bolt assembly from Jay’s CAS-compatible 5.5” av-bay:
Additional outer structural components can be found on some av-bays, depending on their design:
Additional outer bulkheads: Some av-bays, like the one in Bear Force One, have an additional set of outer bulkheads so that the rods and the u-bolts have four connection points instead of two. These additional outer bulkheads are depicted in the image below of the av-bay in Bear Force One with a slightly blue hue.
Av-bay door: Any av-bay with a sled needs to have a door to access the sled. By default, any radial av-bay will have an av-bay door. This is one of the drawbacks to a radial av-bay design, as any hole in the airframe, such as an av-bay door, could potentially negatively impact the stability of the airframe.
Av-bay airframe tubes for Bear Force One with cutout for av-bay door:
The following are the main inner structural components of a radial av-bay or an axial av-bay with a sled:
Sled: This structure houses all the avionics in a radial av-bay and some axial av-bays, and is designed to slide in and out of the av-bay assembly through the av-bay door for easy access to the electronics. It is convenient, but requires an av-bay door.
Sled housing: This structure houses the sled and essentially gives the sled something to slide into. There are channels cut into the inner edges of the housing that the sled can slide into so that it is held firmly in place.
Inner bulkheads/sled housing bulkheads: These bulkheads have a large section cut out and the edges of the cutout grooved so that a sled can slide directly into the bulkheads instead of sliding into a housing. These are used in the av-bay for Bear Force One, shown below highlighted in blue.
Sled from Jay’s 5.5” CAS compatible av-bay (Left), and corresponding sled housing from Jay’s av-bay (Right). One can see how the sled could slide into the housing and be held still by the grooves cut into the housing that match the rails on the sled:
Avionics bay for Bear Force One with upper inner bulkheads highlighted blue:
The following components are the avionics in a typical av-bay along with their associated components:
Altimeters: These measure the altitude of the rocket during its flight and are used to trigger the parachute deployment.
9V batteries: These are used to power the altimeters in flight. They are encased in a housing we have designed.
9V battery cases: These cases keep the 9V batteries safe and allow them so be more easily secured to the avionics bay.
CAS: Our very own modular avionics unit designed by the avionics subteam. It usually has four layers of adaptable circuitry, and is roughly 2”x2”x2” in size. It will hopefully be used in the SSEP rocket to trigger the stage separation mechanism, but for right now we’re just including it in all of our new av-bay designs, as our goal is for it to become a standard part of our avionics system.
LiPo batteries: These are used to power CAS, and they also have housing units that have been designed for them.
CAS antenna: This antenna would allow CAS to talk to instruments on the ground, but it still needs to be integrated into the avionics system.
PerfectFlite Stratologger altimeter (first), LiPo battery for CAS (second), and 9V battery inside custom-made casing (with cover removed to view the battery) (third):
CAS stack put together (without antenna):
Some av-bays are designed with a specific, unique purpose in mind, so they may have different designs to fit their specifications. For instance, an additional av-bay aft of the main parachute assembly was needed on the SSEP rocket in order to trigger the stage separation system and to ignite the upper stage motors. However, there was not much space to fit this av-bay. So, a small axial av-bay was designed by Hadar to meet these requirements, shown below. Note that it does not have a sled and an access door but instead splits into two accessible parts that are then clamped together when installed into the rocket.
The DAVE blog is intended to keep track of all major developments during our weekly meetings. Major progress updates and role assignments will be summarized in the main DAVE page.
Initial tasks assigned as follows:
Created Trello board (must log in, message in #payload-dave for access):
Tasks
People
DAVE Ejection (2)
Work with Recovery and Airframe to determine ejection mechanism/system for glider
Discuss stretching payload section on BFO
Special manufacturing feasibility: cutting into fiberglass??
Ground testing
Determine upper limit of specs (weight)
Brandon
Jay
Rajiv
Joseph
DAVE Aerostructures (3)
Unpacking system
Fabric engineering
Modular cargo integration (at least 1 up to however many we can feasibly fit)
Fasten them onto mounting plates
80/20 (T-slots)
Flight control surfaces
Determine upper limit of specs (weight)
Michael
Rebecca
Jared
DAVE Avionics (2)
Autonomy (Ardupilot, etc.)
Manual control
Radio communication (COTS or custom)
Actuation of servos and any pyrotechnic devices
Jason
Jones: Testing Unidentified Object Drone (1–2)
Alternatives if we are too broke: work with UAV club or get a STAC weather balloon
What are we carrying: just the glider (3–4 lbf), glider and cargo (7–8 lbf), or the whole payload section (14–15 lbf)
Radio and release
Diplomat Jared
Bryant
DAVE Legal (0 unique)
Ensure FAA compliance and waivers
Ensure NAR/Tripoli requirements are met
Communicate with relevant launch sites
Communicate with UCPD for testing
Priyan
Rebecca
a step by step breakdown of assembling and manufacturing the avionics bay, as well as key design decisions that were made.
Sand Paper
Filers
Phillips screw driver
Drill and drill bits
Respirators (when filing fiberglass)
Epoxy (JB Weld ColdWeld ™️ Steel Reinforced Epoxy)
bulkhead jig (designed to correctly place bulkhead and keep level
Unfortunately for this assembly/manufacturing process to epoxy the avionics bay into the airframe became more inconvenient due to the need to epoxy the door nuts to the airframe. As a result, we must assemble the av bay in the airframe tube layer by layer. The components once within the av bay will no longer be accessible, apart from the sled and electronics mounted on it.
Sand down the inside of the airframe tube that you will be epoxying to
NOTE: sand down enough to remove the first layer but not enough to break down the fibers of the fiberglass
Make sure you are wearing a respirator, gloves, and long sleeves
Using a handsaw or sharp dremel bit, cut the threaded rods to length
Note: if using a dremel be aware that the rod can heat up, wear thick gloves on the hand holding down the rod
Using 5 minute epoxy, glue the PLA bulkhead and wooden bulkhead together for the top and bottom sections of the av bay
Allow this to set for at least 10 minutes, you can place a weight on top to hold each subassembly together while it cures.
Be sure to prevent any excess epoxy from pooling out from the sides of the seam (this will change the physical outer diameter and make it more difficult to slide into the airframe tubes)
Drill out the holes of the PLA and Wooden bulkheads once the epoxy has cured to ensure the wires can pass through them easily
Align the Aluminum Bulkheads with the PLA bulkheads and drill out the holes once again to ensure wires can pass through the assembly easily
Insert the U Bolts into the Aluminum Bulkhead and attach the nuts on the other side
take care to make sure the nuts are level
Add epoxy to the underside of the bulkhead between the nuts, ubolt, and bulkhead
Add epoxy to the top of the bulkhead at the interface of the ubolt and the holes
allow that to cure
This is done so that we can be assured of the fit of all components before we assemble the av bay within the tube
Begin first with the sled and work from the "inside" outwards
PLA bulkheads around the sled on the top and bottom
this is a great time for any final filing to ensure the slide can slide in and out smoothly
Slide the threaded rod past the first bulkhead, and add 2 nuts
run the threaded rod past the second bulkhead and add an additional nut on the exterior side of each bulkhead
adjust the nuts so that the assembly is secure against the surface of each side of the bulkhead (the nuts serve as placeholders)
check that you can slide the sled in and out easily and tighten or loosen the nuts as needed
add an additional nut ~1 inch away from each of the most exterior nuts on the threaded rod
repeat for the second threaded rod
add the aluminum bulkheads to each side
adjust the outer most nuts as needed to ensure the aluminum bulkhead is level! and the ubolt is gently touching the wooden bulkhead
add the wingnuts to the exterior of the aluminum bulkheads to hold them in place
make a final check that the sled is still able to slide in and out of the assembly and that all the nuts are properly tightened
then you take off the wingnuts and the aluminum bulkhead
leave the rest of the assembly together
Test that you can slide the assembly into the tube and file as needed
Place the assembly into the tube and mark where the epoxy for the first bulkhead will be placed
Note that this is especially difficult and limited for BFO specifically because of the accessibility and mounting requirements of the av bay
Begin epoxying procedure using JB Weld: https://docs.google.com/document/d/1DCgi2xNbCKLSVA-2AojZUtkCFQReliQGcxFavwJx-4g/edit
The procedure for the first bulkhead is the airframe standard for epoxying bulkheads into the airframe tube
The first bulkhead (put in place prior to the sled) can be done normally, with two precise fillets on either side done by hand.
The specific epoxy will depend on the material of the bulkhead and the material of the airframe.
in this case we have a fiberglass airframe and an aluminum bulkhead and are using JB Weld Epoxy
INSERT SLED INSERTION PROCEDURE
For the second bulkhead, Make a ring of epoxy on the inside of the airframe, pull the bulkhead past the ring of epoxy to create a fillet on the inaccessible side (recall we are assembling this av-bay layer by layer)
After the first fillet has set, on the remaining exposed side make a standard epoxy fillet
let set
To hold black powder vials close to the middle of the rocket so it will not blow through the side of the rocket.
Further improvements will be made relating to the holders to secure them to the bulkhead instead of having them unrestrained during launch
Attached is an external link to a payload subsystem report written for the 2020 Sounding Rocket Design Challenge, last updated in June 2020.
2020 Sounding Rocket Design Challenge Website
This report is intended to be used as a reference for all IREC 2020 payloads, as a preliminary description of all projects.
Excerpt (Abstract):
The Payload subteam of Space Technologies And Rocketry (STAR) at the University of California, Berkeley focuses on launching scientific instruments and experiments to high altitude: we are what makes rockets worth flying. This academic year, the payload projects, all integrated into a 5U CubeSat payload structure, include: onboard cameras, a dual sensor suite and cosmic particle detector, a microbial fuel cell, and an active stabilization system. The overarching mission objective is to record data and test experimental systems in-flight.
The Microbial Fuel Cell (MFC) was inspired by NASA Micro-12 studying MFCs for the purpose of wastewater treatment and electricity production. The purpose of our MFC payload is to determine the effects of rocket launch and flight on the performance and health of the MFC.
The first iteration of MFC was designed to to use wild-type Shewanella oneidensis bacteria in a LB broth with platinum electrodes. The bacteria were sourced from Adam Deutschbauer's Lab at LBL. However, due to the difficulty of the project and a fungal infection that wiped out the bacterial culture, we decided to pivot to a more robust and simpler design.
The second iteration of the MFC was designed to use electrogenic soil bacteria from locally sourced soil, mixed with distilled water with graphite electrodes. The maintenance of this iteration of the MFC was much easier and a control MFC of this design was manufactured to gather voltage data over the course of 2 weeks.
The IRIS project combines two previous payload concepts, IRIS Legacy and Muons. The collective project can be referred to as IRIS for short.
The IRIS project combines two originally separate projects (IRIS Legacy and Muons) into a 1U CubeSat unit to conserve space in the payload structure.
Rajiv Govindjee, Jason Xu, Bryant La and Ocean Zhou are the main contributors to this project. Rajiv and Jason worked on the first iteration of IRIS while Jason and Ocean worked on the first iteration of Muons. It was decided for the sake of efficiency and adventure that the two detectors should be combined into one complete detector. Jason was heavily responsible for the electrical design of IRIS, in particular the printed circuit boards (PCBs). Bryant and Ocean worked on the mechanical integration of IRIS to the rocket. IRIS is currently in its assembly phase, although with the impacts of the COVID-19 pandemic, the assembly phase has faced delays.
IRIS Records Information via Sensors (IRIS) is a sensor suite printed circuit board (PCB), outfitted with an accelerometer, a gyroscope, a magnetometer, a barometric pressure sensor, and a High-G accelerometer. Its function is to record various flight data (acceleration, angular velocity, absolute orientation, barometric pressure/altitude) to assist in developing flight-critical avionics and validating current and future simulation work with respect to flight dynamics.
The IRIS assembly consists of three main PCBs. In order, from bottom to top, the three main PCBs are:
a power distribution board (IRIS-Power) connected to a two-cell (2S) 8.4V lithium polymer (LiPo) battery
a primary IRIS board (IRIS-Core)
an auxillary IRIS board (IRIS-Core)
The first iteration of Muons was based heavily off of Spencer Axani's project. He is a current particle physics PhD student at MIT! This is the website that contains all the info about his project. The GitHub page that includes all the software, details, PCB soldering guidelines for this project can be found here. Our first detector was basically following his step by step instructions and recreating his detector. So to Spencer, a massive massive thank you!
In addition to the motion sensors, there are two optional components on IRIS that are currently unpopulated but can be implemented in the future.
IRIS supports the addition of a GPS module (uBlox cam-m8) in the future.
IRIS supports the addition of a differential pressure sensor, for implementing an external pitot tube in the future.
The electrical hardware (PCBs) are avaliable on our cadlab:
IRIS-Power occupies the bottom most board of the 3 board stack. The primary purpose of IRIS power is to output regulated power from the 2S LiPo, gauge the LiPo's charge with a battery fuel gauge IC, and provide a backup source of power in case the battery fails or is suddenly disconnected. The backup is provided through 2 supercapacitors that can provide several minutes of backup power.
Additonally, the power board has the ability to automatically switch to a connected USB-C power delivery adapter in order to save battery charge during bench-top testing and programming.
IRIS-Power provides 5V for the Teensy 4.1 MCU on IRIS-Core, 3.3V for other extra ICs, and 29.5V for the photo-multipler Muon sensor.
IRIS-Core is the primary module of the 3 layer stack. The middle board of the 3-layer stack is a full-fledged IRIS-Core board, while the top board of the 3-layer stack is a partially populated IRIS-Core board.
The main MCU of IRIS-Core is a Teensy 4.1, an Arduino compatible board.
The full-fledged middle module contains a Teensy 4.1, IMU breakout board, High-G accelerometer breakout board, and a muon sensor.
The partially-populated top module contains a Teensy 4.1 and a muon sensor.
For some very useful diagrams detailing the pinouts, peripherals, and power flow connections, see the following pages:
(12/06/20): There is no way to fasten a nut on a screw from inside the enclosure. The enclosure will be secured to the T-slotted rails with eight screws going through eight brackets, held in place by having the screws serving as pegs into slots. The screws are at different heights, so interference is not an issue.
(12/06/20): The backboard support PCB has been replaced with the stack connectors (pin headers) pictured below. This was done for simplicity of design, to reduce the space taken up by the PCBs, and to prevent interference between the vertical threaded rods and the fasteners attaching the enclosure to the T-slotted rails. The enclosure and spacers have been updated to accommodate this change.
The enclosure measures 7.9 cm x 7.9 cm x 10.635 cm, and can be manufactured via 3D printing with PLA material.
(12/06/20): The PCBs were ordered and arrived. Bryant La will solder the components on campus with a reflow oven over winter break, with Jason Xu's remote assistance. Boards will be shipped to Jason Xu for him to attempt soldering without a reflow oven, though he does not need to succeed for the project to progress.
The BOM is being finalized and the parts will be ordered soon. Once fully manufactured, the code will be rewritten to interface with the combined IRIS/Muons.
(01/25/21): Both Jason Xu and Bryant La are near campus and will work together to finish manufacturing for this project.
(02/14/21): The power board and one of the sensor boards have been soldered. Jason Xu and Bryant La will need to procure the existing completed Muons boards from the Supernode locker to move their scintillators onto the new IRIS/Muons boards. After soldering of the final board is complete, efforts will be focused on writing the board firmware.
At the time of writing (May 2020), due to power and launch issues, IRIS has been unable to record data during flight for any launch. Data obtained so far has been limited to what IRIS senses during assembly on the ground, which showed little variability as expected; however, the values IRIS reports are accurate (e.g., the barometer shows atmospheric pressure near sea level), which is evidence that the sensor suite functions as it should.
Muons has been launched like IRIS and was able to record data during flight. However, due to the minor detector malfunction, relating to multiple data files being saved for unknown reasons, the data obtained was unable to offer much use; besides total muon count, it was impossible to pinpoint which files corresponded to different points during the flight. Nonetheless, the fact that the detector was able to record muon count and that the muon counts increased over time indicate that the detector is able to function properly during flight.
The previously assembled detectors have been tested twice. The first test was to ensure that the measured voltage signals matched the expected values, in which the detector succeeded. The second test measured how the angle of the scintillator (with θ = 0° being the horizontal orientation) affected muon count measured within an interval of 1 minute. This was done to decide the orientation the detector was to be at inside the rocket. Having the scintillator at a horizontal orientation yields the most counts.
Providing 3-axis rotational stabilization for a (hypothetical) component during ascent!
We have a base containing large electronics supporting our servos and arms. Each servo provides rotational motion to one axis with range of +-90 degrees (180 total), with an initial configuration of all axes being orthonormal to each other. The first servo is attached to our base, which controls an arm that our next servo is mounted to. This second servo controls the next arm that our third servo is mounted to. Our last servo, however, does not control an arm, instead it controls a platform, the platform which we would like to stabilize.
All electrical components below, unless otherwise specified, we have in inventory. For everything without a number or description, assume we have one part in inventory.
Arduino Nano
Connects all components together and provides communications/calculations between components.
1S 3.7V Lipo Battery
Power source for stabilization.
Booster Converter (many extra)
Need 5V for most (all?) components, and the lipo only provides 3.7V, so we use this to step it up.
Photo-relay (still needs to be ordered)
We don't want to waste any power before launch, so we can use a photo-relay to only allow current to the servos once the MPU's detect launch.
Resistor (330 Ohms, have extras)
We need one resistor to connect to the photo-relay to have it perform to expectations (ideally it would be 336 Ohms).
MPU's (x2)
One MPU is attached to the base of our stabilization unit, this gives us gyroscopic and acceleration data of how the rocket moves through time. This MPU also provides data so that we can provide the adequate torque to our servos to stabilize the platform. Our second MPU is mounted on our platform, this will provide data for how well our platform is being stabilized. We can take both our MPU's data and record it to the SD Card.
Servos (x3)
Provides mechanical control of the three arms (be wary of Gimbal Lock problem).
MicroSD Card
Provides storage for sensor data, which we can analyze after launch.
MicroSD Card Breakout Board
A board which provides us the ability to write to the MicroSD card using the arduino.
Protoboards (many extra)
A board so we can solder some of our components (like the Arduino Nano and Photo-relay) and keep them reasonably secure during launch.
Wires (stranded, 26 gauge, 50 feet)
Electrons
Servo Extensions (many)
The most convenient way to connect our servos to the power and arduino.
Lipo Connectors (many)
The most convenient way to connect our lipo to the converter.
1S Lipo USB Charger
A convenient way to charge our lipo (before testing and launch, not during).
Servo Bolts
Servo Nuts
Sensor Bolts
Sensor Nuts
Arduino Bolts
Arduino Nuts
Arduino Spacers
MicroSD Card Breakout Board Bolts
MicroSD Card Breakout Board Nuts
Booster Converter Fasteners
Purpose: To constrain the payload structure along the long axis of the rocket
Important design considerations:
We used flight data and openrocket simulations to estimate maximum acceleration loads at 16 g's
Two #4 threaded rods are spec'ed to a FOS of ?????
@Ritvik something about having two possible orientations to minimize issues in assembly
What we have one:
Complete test fit of design
What is left to be done:
Add to launch-day parts list
GPS mounting is designed to attach the GPS module on the inside of the nosecone. In the designing process, two important factors were considered, stability, and suitability. Also, there were restrictions which are the GPS mounting can't touch the top metal plate of the structure and the GPS antenna should be mounted straight.
For higher stability of the GPS module, mounting has 6 zip tie holes on the front. There are two ways to fix the battery and GPS module into the mounting. 1) Using zip tie, combine together battery and GPS module. 2) Or, insert the battery and the GPS module into the mounting and tied them up together. The GPS mounting and holes are small, so a tweezer is needed to assemble it.
For the suitability of the mounting, the rear side of the mounting is designed with the same curvature as the inside of the nosecone. Also, the curvature was measured at 10.5 inch far from the top plate of the primary payload structure.
Payload Structure :
1/16” Steel ballast plates (32)
9” Miniature T-slot rails (8)
4 1/2” Miniature T-slot rails (4)
Aluminum leaf springs (4)
Top base plate (1)
Center base plates (2)
Top aluminum bulkhead (1)
Bottom aluminum bulkhead
Wooden bulkhead spacer (1)
Tie down rods (2)
M3x35 button head screws (4) (Needs purchasing)
M3 hex nuts (44)
L brackets (64)
MX10101 nut plates (64)
MX10101 button head cap screws (64)
M3x10 button head screws (24)
M3x20 button head screws (8)
Adjustable wrench
5/64” allen key
ASSEMBLY
Place 4 long t-slot rails on each corner of the top base plate.
Attach rails to base plate through 2 L brackets on each corner of base plate.
Using 2 M3x10 screws and 2 hex nuts on each corner, fasten each screw with all screw heads facing out of the opposite side of the t-slot rails.
Using 2 nut plates and 2 cap screws on each corner, attach other end of L bracket to t-slot rails by connecting nut plate through t-slot rail and screwing through the hole of the L bracket with cap screw.
Attach MFC payload in payload structure.
Push 4 cap screws through each leaf spring and screw on nut plate to each side of leaf spring.
Slide leaf spring through t-slot rails until top of leafspring is 0.9” from top of t-slot rail.
Repeat step 7 for each side of structure (4 total).
Repeat step 3 and 4 on other end of t-slot rails.
Attach center base plate to the top of t-slot rails by placing M3x10 screw through L bracket hole with screw head on same side of t-slot rails and hold.
Place L bracket through end of screw with tall end facing corner and tighten with hex nut.
Repeat steps 10 and 11 for each L bracket.
Repeat steps 1, 2, 3, and 4 with each corner of center base plate.
Repeat steps 3 and 4 on top of t-slot rails, instead letting drop to bottom of t-slot rails.
Hang 32 ballast plates on the bottom brackets.
Push the M3x35 screw through slots of ballast, ensuring the screw heads point towards open end of structure.
Secure the ballast by tightening hex nuts on opposite end of each M3x35 screw.
Attach Stabilization payload to structure.
Repeat steps 3 and 4 on top of t-slot rails.
Repeat steps 10, 11, 12, and 13, instead using the shorter t-slot rails.
Attach IRIS/Muons payload to structure.
Repeat steps 3 and 4 on top t-slot rails.
Place top bulkhead on top of t-slot rails.
Push M3x20 screws through L brackets with screw heads facing opposite the t-slot rails and fasten with M3 hex nuts.
Place wooden spacer on top of top bulkhead.
Place bottom bulkhead on top of wooden spacer.
Turn entire structure on its side so that t-slot rails are horizontal.
Push tie down rod through slit on the top base plate, through entire structure, and stopping once it is through the bottom bulkhead.
Repeat step 28 with the other side of the structure.
Screw hex nuts onto each end of tie down rods, tightening until the structure has tension.
Flip structure so that it is resting on the bottom bulkhead.
The Cameras project uses the Mobius Maxi camera mounted on a custom base plate that is epoxyed on the airframe's exterior with a custom shroud.
Two shrouds shall be mounted. The camera shrouds have been optimized to maximize field of view while minimizing impact to the aerodynamics of the airframe, allowing the cameras to record the flight with as much detail as possible without being a detriment to vehicle performance. The recorded results are retrieved from an in-camera SD card post-landing. The captured footage should theoretically document the rocket in flight even after it escapes visual range from the ground.
Each Mobius Maxi measures 7.1 cm x 3.5 cm x 1.8 cm and weighs 52 g. Each shroud measures approximately 13.2 cm x 4.1 cm x 3.8 cm and will be manufactured from PLA material using 3D printing.
At the time of writing, no in-air flight recordings have yet been captured. Recording testing has been performed, but the full extent of camera capabilities have not yet been documented. A battery life test has been completed along with a shake test to mimic the turbulance he camera would experience while on the rocket. The Camera was able to record for over 2 continuous hours with minimal quality degrigation as a result of shaking. Worst-case test is planned in the future, with active external heating to mimic launchpad conditions.
CADs are for the camera's custom shroud.
The primary risks and failure modes associated with Cameras are depletion of the battery and structural failure of the shroud during flight. The camera shroud could sheer off from the baseplate, take damage from shaking from not being properly secure in the shroud. Test on different epoxies are being conducted to determine which would best minimize the risk of the camera seperating from the body of the rocket, with the possibility of grooves being put in place to increase surface area contact.
Without power, the Mobius Maxi camera cannot record data. Mitigation strategies include fully charging the camera the night before and setting the video recording settings to their lowest power consumption setting.
Structural failure of the camera shroud would cause parts of the shroud or the entire shroud to shear off of the launch vehicle, potentially even changing the vehicle's trajectory. Mitigation strategies include printing the shroud at higher densities and out of stronger materials, and checking again that the shroud is properly mounted before launch.
Charge both Mobius Maxi cameras with MicroUSB cable.
Place one MicroSD card into each camera.
Configure settings on both cameras to be appropriate to flight mission and launch conditions, including recording automatically when power is turned on.
Turn cameras off.
Place shroud onto the baseplate with lens oriface towards fins and align the two holes on the shroud with the corresponding two holes on the airframe.
Secure the lower, fin-most hole with the nut plate on the other side of the airframe wall.
Place camera into shroud so the lens faces the fins.
Secure the upper hole with the nut plate on the other side of the airframe wall.
Secure the shroud cap onto the shroud, ensuring that the locks snap fast onto the side of the shroud. If uncertain, apply adhesive.
Remove lens cap from camera.
Turn on camera and start recording.
Repeat steps 5–11 with second camera on opposite side of launch vehicle.
Retrieve all payload components from the downed rocket.
Turn cameras off and stop recording.
Disassemble camera assemblies.
Read and analyze data from the SD card.
The description of the Cosmic Watch, a pocket-sized detector that counts the number of muons that hits it. It also measures temperature and time. It will be merged with IRIS for IREC 2020.
PLEASE learn how to solder printed circuit boards. Though it is not hard to pick up, learning understandably still takes time. At Cal, you can either practice soldering in the Chen-Ming Hu Lab in Cory Hall Second Floor (aka SuperNode), or in the Electronics Lab in Jacobs Hall. Here's a tutorial to get you started: https://www.youtube.com/watch?v=Qps9woUGkvI
Find a way to machine the scintillator if the one you bought is not already machined. The manufacturing drawing is attached below: https://github.com/spenceraxani/CosmicWatch-Desktop-Muon-Detector-v2/blob/master/CAD/Scintillator%20CAD%20file.pdf
After you purchase the SiPM and it arrives, PLEASE place it somewhere safe and load-free. Do NOT crush the SiPM as it is very delicate (and expensive!)
Buy all required electrical components
For the Arduino Nano, be sure to upload the coincidence.ino code to it, as this ensures a muon will be counted! Refer to pdf attached below for specific detail.
Solder the electrical components onto the 3 PCBs (Main Board, SiPM Board, SD Card Board). Use this as the guide to know where to solder the components: https://github.com/spenceraxani/CosmicWatch-Desktop-Muon-Detector-v2/blob/master/PCB_Files/SMT_reference.pdf
Drill 4 mounting holes into SiPM PCB. Polish it afterwards.
Wrap the scintillator in reflective foil.
Put optical gel on SiPM board and mount it to scintillator using the mounting holes on the SiPM board.
Wrap both with electrical tape to make light tight. Important! Carefully wrap or else "light-leak" will occur. This will distort your results!
Plug the SiPM PCB into the Main PCB through the header pins.
Finally, upload the SDCard.ino code to the Arduino Nano.
Plug in a 5V power bank to the detector and make sure that the HV pin on the Main Board delivers 29.5 V.
For greater detail, read the entire instruction manual: https://github.com/spenceraxani/CosmicWatch-Desktop-Muon-Detector-v2/blob/master/Instructions.pdf
Please make sure you have access to the STAR GrabCAD! If you do not, you will be unable to locate any of these files*
Also make sure you have SolidWorks 2019 and Ultimaker Cura 4.4.1!*
Please also purchase a Makerpass for Jacobs Hall Access. It will make your life so much easier for assembly*
After you obtain your Makerpass, get training on the Wood Laser Cutters, Ultimaker 3D Printers, Electronics Lab, and FabLight metal laser cutter (this last one isn't really necessary but it's so fun that I think you should still do it!).
The detector CAD is located in the IREC 2020 GrabCAD under:
Upper_Section -> Payload -> Muons_IRIS -> Detector_CADs -> IREC20_PAY_MuonDetector.
Under the Muons_IRIS folder, the other folder called "STL Files". These are the CAD files in the Detector_CADs folder but translated into .stl files which can be passed in Ultimaker Cura and in turn be 3D printed.
While we did collect data from our AirBears launch, it correlated only time with muon count. Furthermore, 4 separate SD files were created, meaning we had no idea at which height did the counts correspond to, making the data not as useful.
To combat this, our beloved payload lead Jason Xu (Woo!) is working to merge IRIS and Muons together as IRIS records height (through pressure) which allows us to see how muon count correlates with other parameters besides time. Excited events to come!
IRIS: IRIS Records Information via Sensors. By Jason Xu, Rajiv Govindjee, Bryant La, and Josh Alexander.
The IRIS journey started in 2018; IRIS v1 was conceived of as a project for the Hands-On PCB Engineering (HOPE) DeCal. The board was assembled in Fall 2018 and found to be relatively functional, with difficulties arising mostly due to lack of software libraries for the ICM 20948. IRIS v2 was designed and assembled in early 2019, adding rounded corners, more sensors, options for breakout boards, test points, improved power electronics, and more. IRIS v2 was also more successful on the software front; all sensors tested worked nominally, including the ICM 20948. Code for IRIS v2 can be found at https://github.com/calstar/Payload. While IRIS v2 was intended to fly on Spectre, STAR's ambitious entry for IREC 2019, Spectre was never constructed due to significant engineering challenges.
For a more detailed look at requirements and progression of IRIS v1 and v2, see the IREC 2019 documentation: IRIS
IRIS v2 was flown on AirBears on 2019-11-16. To prepare for this flight, the casing was significantly re-designed to integrate with the other payload (Muons) on the test flight. Software was completed to allow for continuous recording of IMU data to the on-board SD card on the Teensy.
Unfortunately, as a result of non-comprehensive assembly procedures and some time pressure to assemble the payloads, IRIS was flown while not in a recording state.
The following recommendations were made following this test flight:
Implement some method for back-up power (capacitor, coin cell battery, etc.). This ensures writes to non-volatile memory have time to safely complete.
Create robust procedures and test them entirely before launch. This includes all integration needed with other payloads. Add special notes if power may not be disconnected from the payload after a certain point.
Perform as much assembly as possible beforehand. Ensure that no more than 30 minutes are needed at launch for assembly; time someone actually completing this assembly beforehand.
The team is currently working on physical design and manufacturing for IRIS to fly in the IREC 2020 payload suite as one of 5U worth of CubeSats. Work is also underway on a potential IRIS v4 board, although not required for competition readiness. Software is the largest hurdle for the competition; some development may be required to communicate with all sensors on multiple SPI buses at once (effectively).
A place to learn more about the club, the different subteams, and our projects. This is a helpful resource for outreach events, where you'll be asked various questions about the club.
We are UC Berkeley's competitive high-power rocketry team. We build rockets! Our mission is to enable students from all majors and backgrounds passionate about aerospace to gain hands-on experience through real-world projects. As part of STAR, members can expect to develop a set of valuable engineering skills, including experience with manufacturing, 3D CAD, simulation, project management, and more. For more information, check out our website at https://stars.berkeley.edu/!
Airframe
Avionics
Payload
Propulsion
Recovery
Operations
Simulations
Systems
Business/Finance
Outreach
Media
Ursa Minor: subscale for our entry in NASA Student Launch 2017
Ursa: our entry in NASA Student Launch 2017
Sub-Arktos: subscale for our entry in NASA Student Launch 2018
Arktos: our entry in NASA Student Launch 2018
AirBears: our 4" diameter test rocket, launched in Fall 2019
Bear Force One: 2020 launch vehicle, intended for IREC 2020 (competition cancelled due to COVID-19)
LE-175 "Hot Take": our liquid engine LOX/Kersoene test article
ELLIE: Our GOX/ethanol liquid engine test stand: successfully hotfired in May 2022
SSEP1: UC Berkeley's first stage separation rocket. Successfully launched at the Friends of Amateur Rocketry site in September 2022.
MINDI: UC Berkeley's First minimum diameter vehicle. Successfully launched at the Friends of Amateur rocketry site, smashing the current Cal altitude record at a whopping 14,325 feet!
ALULA: STAR's first flyable liquid engine! Set to hotfire March 2023, and fly soon after!
DAVE: STAR's first glider payload will deploy out of Bear Force One to carry payloads for longer periods of time.
CalVistor: STAR's entry into the IREC 2023 10K competition. Features a 6 inch diameter airframe, dual side dual deploy recovery system, and some epic payloads: muon detectors and a seismograph!
Check the website for more details, as well as our Launch History.
Is there an application?
No! We do not have an application, and we accept any and all interested members. STAR has championed our no-application policy since our founding in 2016.
Is there a membership fee?
No! STAR is completely free to join, and there is no required membership fee. During a normal semester, many of our members opt to obtain the Jacobs Hall makers pass but this is entirely optional. Expenses made by members for club purposes (ie. buying raw materials and parts for our rockets) are usually reinbursed by the club (subject to subteam lead approval).
No! A large majority of our members joined with little to no prior experience in rocketry. Yet through our own passion and motivation, we have been able to create fully functioning rockets! While having technical or business experience is nice, we primarily expect from our new members two things: passion and dedication.
No! In addition to some of the non-technical teams mentioned above, one of our primary goals is member development and education. We have had a large number of members in non-technical majors do design, engineering, building, manufacturing, and testing of all different systems. With workshops and a mentorship program, we hope to teach all the tools you’ll need so that anyone who wants to is able to contribute.
You can check out which of the subteams interest you and attend their meetings or talk to the leads in-person or on Discord. Once you have a subteam you're interested in, there is an intro project that you should complete to join the subteam. The intro project is not meant to be a homework assignment or something you have to tackle alone. There will be office hours and workshops to help you complete it, and we encourage collaboration!
You'll find all the practical info you need on the New Members page:
Twice per week. General Meetings ("GMs") and subteam meetings are usually two hours each every week. You might also meet outside of regular meetings for build days, design reviews, or other to hang out and gain subteam points! GM's this semester are Thursdays from 8-10 PM in Jacobs Hall and Subteam meetings are Mondays 7-9 PM in Etcherverry Hall!
Design and manufacture launch vehicles
Includes the structure, materials, aerodynamics, and stability of the rocket
Help integrate the systems of other subteams
3-D model using SolidWorks and OpenRocket
Perform composite lay-ups to create airframe components.
Use a CNC tube winder to manufacture tubes and other airframe components
Mechanical design, systems engineering as needed
We are designing and building the airframe for our 6-inch diameter IREC rocket with a target apogee of 10,000 feet; this includes tubes, fins, the motor mount, couplers, brackets, fasteners, and more.
Make flight electronics systems and corresponding ground systems
Design custom circuit boards, flight software, ground station software for telemetry and analysis
Antennas, wiring, and interfacing with other elements of the vehicle
Electrical and software design, mechanical as needed
We are designing and assembling the entire system architecture for Spectre. This includes flight computers, telemetry and power control, sensors, and more. The design cycle started with deriving requirements, and selecting key components, and moved into PCB (Printed Circuit Board) design (schematic and layout). Currently, we're working on revising the PCBs and starting to write firmware and software for our platform.
Develops experiment concepts for payload challenges
Designs payloads and collaborates on interfaces with other teams including Airframe, Avionics, and Recovery
Manufactures the payload! Payloads are primarily composed of custom parts made in Jacobs and the Etcheverry Hall machine shop
Runs through tests to ensure the payload suite meets all specs
Science, mechanical and electrical design, software as needed
The payload is what the rocket is carrying, typically a satellite, scientific experiment, or even humans (for larger rockets).
Upright landing and target detection (SAGITTA-VL ... no one knows what this stands for)
Autonomous rover including mechanisms to separate the airframe (black powder charge) and push out the rover (scissor lift). Rover's mission was to drive 5 feet and deploy a set of folding solar panels.
Cosmic ray (muon) detector
Sensor package (pressure, acceleration, orientation, angular velocity, temperature, humidity, etc.)
We are designing and building a whole suite of science experiments and sensors to fly to a height of 10,000 feet.
Responsible for putting the rocket in the air
Building the engine for the rocket
Combustion, fluids, cryogens, mechanical and some electrical design
Specifications for software
We are building a prototype liquid bi-propellant engine. Design work in progress includes designing test structures, an integration structure, and improving parts of the engine itself.
Responsible for the entire descent of the launch vehicle, including pyrotechnics and parachute deployment
Ensuring a safe landing of the vehicle
"Jack of all trades" subteam with tons of hands-on work
Fabrication, Electronics, Physics, CS, Systems
We are developing a novel stage separation mechanism, as well as managing the recovery of all launch vehicles in development.
Manage and enforce team-wide safety standards
Handle launch operations, checklists, and integration of the launch vehicle
Organize and maintain our GitBook!
This includes both tutorials and project-specific documentation behind-the-scenes
Technical design reports for competition
Launch checklists, procedures, and FMEA
Manage project-wide testing and verification of parts and systems
Make sure the inventory is up-to-date and usable
Manage CAD data
Look into regulations and law surrounding rocketry
Having experience working with project documentation is a highly sought-after skill by employers of all kinds. Being able to maintain docs for your project shows that you are organized and capable of communicating your ideas with others. Furthermore, tools like checklists, FMEA/FMECA, and especially unit and integration testing are used heavily in industry, and the Ops team is a great way to get familiar with these early on in your career!
If you're more interested in the safety side of Ops, learning how to work safely with dangerous materials and devices can be a great experience for those looking for or already participating in research or work using lasers, cryogens, high-pressure systems, composites, flammables, etc.
Responsible for Design Verification and Concept Check
Using ANSYS, SimScale, hand calculations, and other computation software
Simulating flight trajectories and fluid dynamics
Stress analysis and hazard identification
Analysis of sensor data from flights
If you're a Berkeley student, you'll have access to a good number of Microsoft and Adobe Software including Premiere Pro.
There are many existing tutorials out there on the web that probably will provide a more detailed step-by-step procedure and description on features of Premiere Pro.
So here, we'll talk about what information you'd want to put in for a club promotional video.
Promotional Videos
Objective
Recruitment: to attract audiences/ potential members to our club
Crowdfunding: to attract donors/sponsors for financial support ex) Crowdfunding
Depending on the objective, what content you want to include in your video will change!
Recruitment Videos
Emphasize the variety of subteams we have (technical AND non-technical)
technical subteams: emphasize projects with short descriptions with minimal jargon
non-technical subteams: emphasize the impact they have/ the non-trivial role they play in the club
present our long term and short term goals so students understand what our team's vision is
Photos
insert images of social activities we have inside and outside the designated club events (i.e. outside of General Meetings)
Clips from our launches are always a crowd pleaser
general tips
sync the audio and the visuals so that the visuals aid whatever the audio recording talks about
transitions look less choppy with 'Cross Dissolve' or fades
Crowdfunding Videos
Emphasize the variety of subteams we have (technical AND non-technical)
technical subteams: emphasize the significance and diversity of projects within the club
non-technical subteams: always include how we aim to give back to the community through education and outreach (not only because we actually prioritize this, but donors love that ;) )
present our long term and short term goals so donors understand what our team's vision is
Photos
Clips from our launches are always a crowd pleaser
As mentioned before, outreach images are also crucial
CADs and layouts/schematics of our projects also spotlight the intellectual value in the projects we do and the knowledge we pursuit.
Including videos of people talking (i.e. interview clip) always adds a nice humanly touch to the otherwise money-hungry typical crowdfunding video
3D model file-sharing!
Starting this year, STAR will be using SolidWorks PDM for version control and file sharing for 3D models. Once everything is set up on the server side, we will update this page on how to access PDM and get it set up!
University policy REQUIRES anyone who wish to work at the Richmond Field Station (RFS) for the first time to complete a short online safety training module. The training must only be completed once.
All leads will strictly enforce this requirement. You will not be allowed to go to the RFS if you have not completed the training AND followed all the steps below to submit proof of completion.
Information about the training requirements can be found at the following website, under the section title "Working at the RFS Training Module". Detailed instructions from the page will also be listed below.
Go to this link, you will be prompted to login with your Calnet identity: https://jwas.ehs.berkeley.edu/lmsi?deepLinkActivityId=247519
If the link above does not immediately work, try this link: https://jwas.ehs.berkeley.edu/lmsi
At the UC Learning Center welcome page, navigate to the correct training course by searching for "Richmond Field Station" and selecting the course "EHS 703 Working at the Richmond Field Station".
Start the training, if you are prompted for Organization, enter "STAR", or if you are prompted for a Faculty Adviser, "Ömer Savaş".
After completing the training, you should have a completion certificate. Take a screenshot of it (instructions to take a screenshot), or save it as a PDF.
You have finished the training BUT you are not done yet. You must submit proof of completion using the following form:
You have now completed the RFS safety training requirement!
How to get paid back after buying stuff for the team.
STAR is a Registered Student Organization under the Associated Students of the University of California (ASUC). As such, our funds are stored in their accounts and must be paid out according to their policies. Probably for better documentation and to ensure all money is spent properly, they only disburse funds after we purchase the items. This disbursement is your reimbursement.
Note: This process has changed to be entirely online since March 2020
Only members can submit a purchase request. In the eyes of the ASUC, our official membership list is on our CalLink page. The following steps will show you how to get on our CalLink roster.
First, go to our CalLink page here: https://callink.berkeley.edu/organization/star/. Sign into your Berkeley account and click Join to request membership. This is a one-time thing, and will allow you to submit a Stage 1 Purchase Request.
You will need to wait for a lead to approve your request to Join. The finance tab will not be available until you are approved. Leads, you must manually mark approved members as "Financial Requestor - 1st Stage" in CalLink for the Finance tab to appear.
We have noticed that the "Join" button is missing sometimes. If that happens to you, just send a message in the #business channel or dm the business lead for a "financial requestor--stage 1" status, along with your Berkeley email and name.
Once you have been approved as a member, again, navigate to our CalLink page: https://callink.berkeley.edu/organization/star/. You should see the following page:
Then, click the STAR icon on the left banner. The icon will turn into a gear when the mouse hovers over it. This will open a sidebar. Click the Finance option.
The screenshot here shows what an admin (usually a lead) can see. If you are a 1st-stage financial requestor, you will only see Documents and Finance on the popped-up menu.
If you do not see the banner, you may be using the old Callink web page layout. Refer to Navigating the old Callink web page layout if this is the case.
Click the Create New Request button and then Create New Purchase Request from the drop-down options.
Fill out this form as accurately as possible.
The PR form asks for your UID. It is NOT your student ID on your Cal One Card. Be sure to follow the instruction on the PR form to look up your UID. We recommend right-clicking the UID link, and opening it in a new tab so that you won't lose progress (if you click on the UID link directly, it may just reload the current page into the new page)
For Subject, use the format [full name] - [subteam] - [item description]. For example, this might look like:
Rajiv Govindjee - Propulsion - Test Stand Hardware
The description of items in the Subject should be brief but descriptive; try to use between 2-5 words. You can elaborate below in the Description field as well.
Enter the Requested Amount; this should be the total for the purchase request. Purchase requests (PRs) are usually one item, but you can theoretically put up to six items on a single CalLink PR.
For Categories, chose Reimbursement - Any amount. If you feel like you must use one of the other categories, please reach out to the Business lead.
Refer to the table below for Account:
As of now (May 24, 2022), all expenditure, regardless of categories, should use our misc account: 3-70-203828-00000-MISC-STAR
.
Fill out the Payee Information completely. If you are getting a check mailed to you, this address is where it will go.
Select an expenditure action
Check out the following chart for more information about three common actions:
We recommend Mail to Payee-same address or Direct deposit
For most cases, you can leave Special Instructions and Event Details blank.
Fill out the required fields for Item #1 (Date, Type, Vendor, Location, Total)
The form asks you to attach receipts: failure to do this will mean the request is rejected. Below is a sample procedure to reliably get your PR approved:
Only complete Step 3-7 if your receipts do not have billing contact (name, address, etc.).
Download or scan and upload an invoice or receipt from the vendor. For Amazon, invoices must show the word "Shipped". For McMaster, it's best to concatenate the Receipt and Packing List (shipping confirmation), but you might be able to get away with just the Receipt (as long as it shows shipping cost).
Redact the invoice/shipping notification as appropriate.
Download a PDF of your credit card / bank statement (and make sure it's not password-protected to edit; you can use "Print to PDF" from your browser if this is an issue).
Use a tool like Adobe Acrobat DC (free for students at https://software.berkeley.edu/adobe-creative-cloud) to redact sensitive information like routing numbers, other purchases, balance, etc. (optional, but recommended).
You will need to leave your name, dates, amount of relevant purchases, and the last 4 digits of your card number _unredacted._ The ASUC can and will reject PRs without this information on your statements.
Verify the invoice total matches the credit card statement total. If it does not, the ASUC will likely reject your request.
Verify the Payee name matches the bank/credit card statement. The ASUC will likely reject your PR if this is not the case. It may be acceptable to have no name on the reciept, but not one that does not match.
Use a tool like Adobe Acrobat DC to concatenate the invoice and statement into one file, omitting any irrelevant pages.
Upload the file.
Repeat the process for Item #2, ... , 6 if applicable. Most PRs contain only one item.
Once complete, check over all your entered data. Upon PR submission, you cannot edit the PR anymore.
Submit the Purchase Request.
Once you have submitted the PR, your job is complete! STAR's stage-2 financial agents, who are usually in the business subteam, will approve your PR or contact you for further questions! If you realize that you have made a mistake, please inform the agents. You can do that either by direct messaging or sending the message to the Business channel in STAR's Discord Server.
If no stage-2 agents approve your PR or contact you after 3 business days, please send a message in the Business channel.
If some of your receipts do not have billing contact (name, address, etc.), which can clear show that they were your purchases, you should prepare a digital copy of your credit/debit card statement proving you paid for these items. (you can redact all irrelevant information, but make sure to leave your name on the statement)
Only follow the steps below if for some reason you were not able to upload the necessary documents to the purchase request, and they have not been added even after the purchase request is Stage 2. We recommend you to complete this step with a Business member
Please e-mail proof of payment (credit card statement or bank statement) to asucfinance@berkeley.edu. The email must include:
The purchase request number in the subject line
The name of the payee
A finance representative from the team will review your request and elevate it to a Stage 2 request. We will check that the amount requested matches the amount on the proof of purchase, and we will check that you have all required proof of purchases.
Once approved, you will be notified through email or Discord. You can also check status from the Finances page.
If your request does not meet our requirements, it will be rejected. Please check this page to make sure you met all the requirements.
Wait for approval from the LEAD Center. They may reach out to you for more details. If your PR(s) are listed in Stage 5, that means your reimbursement(s) have been approved.
Once you have been approved as a member, again, navigate to our CalLink page: https://callink.berkeley.edu/organization/star/. Click Manage Organization in the upper right corner.
Then, click the expand menu button (three horizontal bars) on the upper left corner . This will open a sidebar.
Click the Finance option.
Click the Create New Request button and then Create New Purchase Request from the drop-down options.
Now you are ready to resume the tutorial above. Click here to return.
This is specifically for Macs
Do this BEFORE any part of the solidworks tutorial if you do not have a windows operating system
If you've already downloaded SolidWorks onto your mac, just delete it until after you have completed this tutorial.
VMware is a software that is free for Berkeley students that allows you to run windows on a non-windows computer which will allow you to install and run SolidWorks. Bootcamp is a program native (already downloaded) on macs that also allows you to run windows on a mac. Both options have some pros and cons which will briefly be detailed below. If you already know what you want to use, skip to the directions. If you have any questions/problems with the directions feel free to contact Ananya Subramani on the STAR Discord.
Allow you to run the latest version of Windows
Can run SolidWorks
VMware is easier to start up (like starting up a browser or generally opening up an app)
Boot Camp requires you to restart your computer whenever you want to run in a windows environment
Boot Camp requires you to permanently partition your hard drive which cannot easily be changed after it is done.
Partitioning your hard drive here means that some amount of your drive will only be accesible to the windows boot and the rest will be accesible normally
Main thing here is that you can't get more memory/storage if you need it in the windows portion easily
VMware does not require a permanent partition so the size can change
Boot Camp will run SolidWorks more smoothly because all of your RAM can be used
VMware will be able to run solidworks, but it may not be as smooth because you won't be utilizing all of your RAM
My personal reccomendation is to use Boot Camp if you plan to use solidworks very actively, and VMware if you just want to look at files in more detail than grabcad shows. If you have a lot of RAM though, you could probably just go with VMware and be fine
You will need the following things, or the download will probably fail at some point:
Mac made in 2011 or later
exception: 2012 Mac Pro “Quad Core” using the Intel® Xeon® W3565 Processor
OS X 10.11 El Capitan minimum required
You can check this using the "About your Mac" tab in the top left corner apple drop down menu
>50 GB free storage
Click on Windows 10 and add it to your cart. If you want to use VMware, go to step 2.5, if you want to use Boot Camp, check out and go to step 3.
From the same place you should be in step 2, go to the VMware tab and download VMware Fusion 11.x (for Intel-based Macs). You should get to this screen:
Add VMware to your cart and check out.
In the details of your purchase that you made in step 2, there should be a windows license number, you will need that.
My screenshot doesn't have a Windows license number because it's been more than one month since I "bought" it but yours should.
Select the proper language, and download the 64-bit version
VMware users, go to step 4, Boot Camp users go to step 5
Download VMware fusion from the cart and open and install the application. When it asks for a number during the setup process, enter the serial number that I blacked out in my screenshot.
Once you see this screen, drag the windows 10 iso file into the place where it says install from disc/image (the default name for the downloaded file is shown below)
From here, just go through the installation steps and once you have your virtual machine configured and you can access the internet, go back to the solidworks installation guide and follow those steps *in* your virtual machine.
Using the spotlight search or some other search bar on your mac look up "Boot Camp Assistant" and open the app. You should see the following screen.
From here, hit continue and you should be able to choose your partition size, with the minimum being 42 GB, which should be fine, but if you are willing to dedicate more space to a Windows partition, go for it.
Once you've completed the installation process, you can boot into your windows partition by restarting your mac while pressing the "option" key.
Once you are in your Windows partition, you can go back to the SolidWorks installation guide and download SolidWorks.
SolidWorks (also written as SOLIDWORKS) is a 3D Computer-Aided Design (CAD) program. STAR uses SolidWorks for a large portion of our design work.
SolidWorks is only available for Windows 7, 8, and 10.
You can also use Parallels for macOS or VirtualBox for Linux. Refer to the VMware/Boot Camp setup page for more detailed instructions.
You can also attempt to use other means to access a Windows installation like Chrome Remote Desktop.
Before starting, make sure you have a fast, reliable internet connection and enough space on your disk. This process will download roughly 8GB of data.
If you are upgrading from an older version of SolidWorks, do not delete the old version and then download the new version. The old version can be upgraded.
STAR is migrating to the SolidWorks 2023 Student Edition.
Under product information
Select Yes (I already have a serial number)
Choose 2022-2023 version
The serial number is listed in the discord server under #info
Check the #info channel in the club discord for the serial number.
The download link only downloads a ~32.1MB file named SolidWorksSetup.exe. A 7.1GB-18GB download will take place after following the instructions in the installer if a new installation is made.
Make sure you only install Solidworks, and not any of its extra add-ons like Solidworks Electrical. People have had problems in the past when trying to install extra add-ons.
If presented with the option above in the installer, it is recommended to upgrade rather than create a new installation to save space.
On the summary page of the installer, you can select which products you wish to install. At minimum, you will need the 7.1GB SolidWorks package.
If you are buying... | Use this Account |
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Expenditure action | What does it mean |
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This will only work for Intel-based Macs, not for M1 and M2 Macs. For those, you will have to download Parallels. will help show the process.
Start by going to this website: and taking the link for "personally owned devices." You should be able to navigate to this screen:
Once you have access to that license, navigate to this site:
If you have a UNIX-based operating system on an Intel/AMD chip, consider dual-booting Windows (see for macOS) or running a virtual machine (the campus provides VMware and a Windows license for free).
If you have a , you must use Parallels for macOS as Boot Camp is unsupported on these Macs.
Go to: and complete the form (first name, last name, Berkeley email address, select “student team” on dropdown)
Instructions on downloading and installing SolidWorks Student Edition 2023 can also be found .
If you need more help, can help walk you through the process!
For those of you with M1 and M2 Macs, can help you with the process. may also help. You will need to download to run Solidworks in a Virtual Machine on your Mac.
You should now have successfully installed SolidWorks! If you encounter issues, please contact a lead before moving on. Uninstalling, rebooting, and trying again can resolve many issues. Now that you've downloaded SolidWorks, head on over to and some of our previous to learn how to use it! You can also learn more about our file-sharing platform !
Any hardware for vehicles, engines, or related projects
3-70-203828-00000-MISC-STAR
Social supplies, outreach, etc.; non-hardware purchases
3-70-203828-00000-MISC-STAR
Mail to Payee-same address
No additional set up or office visit needed. However, it takes several days for checks to be mailed to the address indicated in your PR form.
Direct deposit
Electronic deposit, the fastest way to receive reimbursement, but requires additional setup. For more info please check out Section 6A in the PR form
Pick up
No additional set up required; however, you would need to visit 432A Eshleman Hall with a valid photo ID
ANSYS Student is an ANSYS Workbench-based bundle of ANSYS Mechanical, ANSYS CFD, ANSYS Autodyn, ANSYS SpaceClaim and ANSYS DesignXplorer.
To download ANSYS Student, navigate to https://www.ansys.com/academic/free-student-products. Scroll down and select ANSYS Student, then click on the Download ANSYS Student 19.1 button that appears below.
After the folder finishes downloading, unzip it with your favorite unzipping tool and navigate to the new folder. Then, open a file found inside the new folder labeled Setup.exe. Click the Next arrow in the bottom right corner as you progress through the setup. Once installed, you can open ANSYS by searching "Workbench 19.1" in your computer's start menu.
We have experienced an issue once where the workbench application did not install. In this case, delete the ANSYS program file in your C drive and repeat the process above.
At the time of writing this, the GrabCAD SolidWorks add-in is not supported for SolidWorks 2019. You will still be able to change and sync local files to GrabCAD projects, albeit less conveniently.
Upon being added to CalSTAR on GrabCAD, you'll be able to see all our projects.
In order to access these projects locally, first create a folder anywhere in your existing files. (When you downloaded GrabCAD, it by default should have created a "GrabCAD" folder in Documents.)
While the name of the folder does not matter, for clarity, you should name it with the same title as the GrabCAD project you are trying to sync to.
In the GrabCAD Desktop App, you'll have the option of manually connecting a project. Select that option, select a project, and link it to your recently created folder.
In the Desktop app, if you have successfully connected a project to your local folder, you'll be able to see the status of both the local folder and the online Workbench. If the Workbench panel is blue, that indicates that other people have made changes to files within the project and you will need to download these updates.
If the Workbench panel is black and not blue, you do not need to do anything and are completely up to date.
Hover your cursor over the Workbench panel and click to download.
Make sure all changed files are selected and click Download Selected. After all of the updates finish downloading, you should see a green box pop up both in the Desktop app and in the bottom right corner of your screen that says the downloads have finished.
To open a file for use with GrabCAD, click on the Open Folder button in the Local Folder panel, then double click on the desired part in the pop-up file browser. Other methods of navigating to the part are not guaranteed to work (although they may if your files are reasonably organized and you know for certain you are accessing a GrabCAD synced file).
If you do not lock the file you are working on, you may create file conflicts and lose changes!
Work on the file for as long as necessary. It is good practice to save and upload with every major revision, even if you will be working for quite a while on the same part.
It should not require SolidWorks crashing and you losing all your progress in order for you to learn the importance of saving often.
After saving the file with changes, we are now ready to upload. Save the file and return to the Desktop app. You should now see that the Local Folder panel is highlighted blue. Hover your cursor over the panel and click to upload.
In the upload tab, you will be prompted to include a comment describing the upload. Write a descriptive message detailing exactly what you have changed since the last version.
When you are done with this, press the Upload Selected button to complete the process (by default, all changed files should be selected). As before, a green box will pop up notifying you when the upload is done.
If you don't plan on making any more edits in the current session, go back to the online Workbench and unlock the file by right clicking.
You're all done. Again, make sure to unlock the file when you're all finished editing it!
Straightforward version control for CAD
GrabCAD Workbench is an online platform to share CAD files and collaborate on projects, featuring version history tracking. It integrates directly with SolidWorks with a toolbar add-in and a desktop application.
If you already have a GrabCAD account, you can skip this step.
GrabCAD Community and GrabCAD Workbench accounts are the same
Creating a GrabCAD account is a straightforward process, first naviagte to:
In the company details section, choose job level as "Student" first before filling anything else out. The company name section should change to school name; type "University of California, Berkeley" (or some variation thereof) in the text box.
Proceed through the signup process.
Be sure to go to your email to confirm the account.
You've now successfully created a GrabCAD account!
Message the email you used to sign up for GrabCAD to the Operations Lead (@mcelly#1609) along with a copy of the previous paragraph on naming to obtain an invitation to STAR's GrabCAD page. Let them know which projects you need access to, if possible.
The GrabCAD Workbench desktop application allows you to sync CAD files from your projects so that you have a local copy on your computer. It also installs the companion SolidWorks toolbar.
Navigate to the following link to download the installer:
Continue through the installation process. After completing the installation, be sure to log in with your GrabCAD account.
You've now successfully installed the GrabCAD Workbench desktop application!
OpenRocket is an application that uses Java (Version 6 or later) to run. Mac OS generally comes with Java and will update it automatically. For Windows machines you may have downloaded Java for some other application already. To download the most recent version of Java, click .
OpenRocket is free to download and is available . Once at the site, click to download the most recent version. The download should be fairly quick and you can run the file immediately once downloaded, so long as Java is installed.
If you have any issues with running OpenRocket, or just want a slightly easier and improved experience, hopefully has you covered. Read the post for more detailed information, or simply get started in OpenRocket by downloading and running from the links below.
Before starting, make sure you have completed your installation of GrabCAD Workbench. If you have not, please finish the instructions :
Before working or making any changes to a file, first lock the part in the online GrabCAD Workbench by navigating to the part and right clicking. More documentation on locking can be found .
STAR parts currently follow the set naming convention outlined at found under Tutorials --> Operations --> SolidWorks file conventions. All parts in STAR GrabCAD projects created after 2019 must follow this format. If you have questions, just ask in #operations!
You may want to unsubscribe from Workbench emails here (there are a lot!):
How to Connect to CalSTAR's Server for Maintenance, Solidworks Workgroup PDM or Converge CFD Licensing
As of August 14, 2018, CalSTAR's Microsoft Azure Server has been taken offline indefinitely. The server's primary role was to serve as a PDM host, a task taken over by GrabCAD. Its secondary task of hosting Converge CFD license validation was deemed to not be valuable enough to justify continued payment for the server.
In order to use Solidworks Workgroup PDM or Converge CFD, you must be on the same network as our server. Since we cannot physically connect to the same wifi or ethernet connection, we will be setting up a Virtual Private Network (VPN) to link your computer and the server.
As a very generalized example, you can think of a network as a small town, with roads connecting houses and stores. Being in the same town (network) allows you to use the roads to go from your house to the store and back (exchanging files and information with the server).
Staying with this example, a separate network would be the equivalent of a town on the other side of a river. The two towns can not interact with each other. You cannot drive from one town to the other, a home in one town cannot visit a store in the other.
This is representative of your computer and the server right now. The server cannot interact with your computer, and your computer cannot interact with the server. To have any interaction between the two towns (your computer and the server), a physical connection must be made. In our example, this would be the equivalent of building a bridge across the river. You must plug your computer into the same internet (ethernet/wifi) as the server. This is not possible since Microsoft owns the server and it is probably miles away from you.
What we will be doing in this guide is setting up a Virtual Private Network (VPN). In our two-town example, the VPN is basically a quick and temporary bridge connecting the two towns. The VPN will make it seem as if the two towns are one, connected with the same roads. This lets the server communicate with your computer and vice versa. This is necessary in order to share files between the computers (essentially what the PDM and license check does).
In order to set up the VPN with our server, you must install a VPN Client. The following two programs have been known to work well:
Choose one and download the version for your operating system. Read the notes below for your chosen program.
Configuration files for both programs can only be downloaded when signed into Google Drive with a berkeley.edu account.
Make sure you are downloading the SoftEther VPN Client under Select Component
When installing, make sure you are installing SoftEther VPN Client and NOT the Manager (Admin Tools Only)
Proceed with the rest of the installation.
Launch SoftEther VPN Client Manager
Select Virtual Adapter at the top of the window, then New Network Adapter
Click OK (Name should be prefilled as VPN)
Once finished, click Connect at the top of the window, then Import VPN Connection Setting...
Locate and import the 'pdm2.vpn' file you downloaded earlier (probably in your downloads folder).
Select the new connection PDM2 and login with the provided credentials.
When installing, leave the default options checked (select them if unchecked):
OpenVPN User-Space Components (grayed out)
OpenVPN Service
TAP Virtual Ethernet Adapter
OpenVPN GUI
Options in Advanced can be modified as you wish
Configuring After Installation
Launch OpenVPN GUI
For Windows, after starting OpenVPN, the OpenVPN GUI shows up as a computer-with-lock icon in the system tray (icons near the clock and date)
Locate the OpenVPN GUI icon in your system tray, and right click it.
Select Import File...
Locate and import the 'pdm2.ovpn' file you downloaded earlier (probably in your downloads folder).
Click OK
Right click the OpenVPN GUI icon.
Select Connect and login with the provided credentials.
CURRENTLY UNDER EVALUATION. INSTRUCTIONS ONLY AVAILABLE FOR CONVERGE STUDIO (PREPROCESSOR) AND NOT CONVERGE (SOLVER).
Refer to deprecation note in [deprecated] Connecting to CalSTAR's Server.
Converge CFD is a particle-based fluid dynamics solver. It is currently being evaluated by the Simulations team for full team usage. More details about the software can be found here.
There are actually two programs relevant here: CONVERGE and CONVERGE STUDIO. Both are included in our license. CONVERGE is basically the actual solver. CONVERGE is the program that will run your processed input files and return the simulation. CONVERGE STUDIO is a pre-processor where you can view geometries, set boundaries, set simulation options, and export these as input files for CONVERGE. CONVERGE STUDIO is also capable of running CONVERGE in serial, and validating the exported inputs with CONVERGE.
Click here for Converge CFD's Downloads page. You will need to make a new account, or log in with your preexisting account. Upon logging in, a file directory page will be shown.
Select CONVERGE_2.4, then CONVERGE_Studio, then download the appropriate file for your operating system.
There are no special instructions for installation. Simply run your downloaded file and follow the on-screen prompts.
It will be helpful to make a note of your installation directory, as you will need it for licensing.
Since the software is no longer in use, and the license file has been requested multiple times by persons clearly not on the team, the license file is now unlisted and private. Please contact your current leads if you really must use the license file.
The license file can only be downloaded when signed into Google Drive with a berkeley.edu account.
Copy or move the 'license.lic' file into the license folder in CONVERGE Studio's installation directory. For Windows, the default location is
The file MUST be named license.lic or CONVERGE Studio will be unable to locate the file.
The license for Converge CFD is a floating license. This means you must be connected to a licensing server in order to use the software. For CalSTAR, the licensing server is our only server, the PDM server. For instructions on connecting to the server, click here.
Once the license.lic file is copied into the correct directory, and you are connected to the server, simply launch CONVERGE Studio.
You must stay connected to the server while working in CONVERGE Studio. The program will perform a license check out/verification every few hours. This includes simulations. You must be connected during a simulation or it will be terminated after the next license check. Terminated sims can be restarted via the restart file.
For floating licenses, only 5 simulations can run at a time across ALL computers. Please make sure with the Simulations Lead that no other critical sims are running before you start yours.
You only have to do this once! Follow these instructions carefully and everything will be easier later on.
Before moving forward, make sure you have GrabCAD set up in SolidWorks:
Open up SolidWorks
Make sure that your local GrabCAD folders are up to date
Navigate to Tools>Options
4. In the popup window, navigate to "File Locations"
5. Click "Add"
6. Navigate to the top-level GrabCAD folder "IREC18 Templates"
7. Press OK
Now, when you make a new part, this will show up! You can navigate to the IREC18 Templates Tab and select that drawing template when you make a new drawing.
If you don't see this dialogue, click on "Advanced" in the bottom left corner
You're all set! Now when you make a new part or drawing you should be able to navigate to the IREC18 Templates tab and make a new part just like you would normally.
When you create a part, you can still use the default part template (i.e. just make a part however you would normally). This is only relevant for creating drawings.
Some properties in the title block will be automatically filled. We have already determined which ones will update automagically, so all you need to do is the following:
Double click the title block
Some fields should be highlighted in blue
Edit the blue text boxes
Click outside of the title block
And you're done! It's that easy!
If you don't know how to do this, check out:
So you've downloaded SolidWorks, now how do you use it?
We are going to provide different tutorials based on how experienced you are at SolidWorks and 3D modelling in general.
Absolute Beginners
The rest of the tutorials we are about to provide are based on which specialty you are joining!
Airframe/Recovery Tutorial Links
Avionics doesn't really use SolidWorks, but we are working on getting PCB design Tutorials!
Payload Tutorial Link
Propulsion Tutorial Link
Simulations Tutorial Links
Some of these videos will be cross-disciplinary, so if any of them catch your interest, give them a watch and practice them!
You should now know at least the basics of how to use SolidWorks! Just keep in mind, the best way to learn is to practice, so boot up SolidWorks and get to it! (Tip: Always keep a mouse on you if you plan on using SolidWorks! It makes it a million times easier.)
How to make those cool parts that you designed; or, how to design cool parts that are make-able
Broadly speaking, this section covers how to select materials, how to manufacture parts out of stock, and how to choose / work with parts that you cannot manufacture yourself.
If you're just getting started, we recommend going through the 3D Printing and Laser cutting tutorials; refer to the Material Properties and Uses page as needed:
If you have more experience or are a little farther along in the design process, check out some of our other tutorials on how to use commercial parts or where to source stock from:
For more specialized needs, we have a few tutorials on more advanced manufacturing methods:
What good is MSE anyway?
Delrin is a low-friction plastic that is extremely machineable; Delrin parts can be made on a laser cutter or mill. For small, precise parts, the Othermill is a great way to machine Delrin. Delrin is fairly strong, although it will deform substantially under higher loads.
Acrylic (in the form that Jacobs Hall sells) is a fairly brittle material that we recommend avoiding for use in flight parts. Acrylic is occaisionally useful for enclosures or signs. Polycarbonate is recommended as a substitute for acrylic unless the material must be laser cut.
ABS is a common 3D-printing plastic. It is slightly more ductile than PLA, the other common printing plastic, but otherwise similar. While there is a common perception that ABS is "stronger" than PLA, this is somewhat inaccurate; for most uses, they are indistinguishable.
6061 aluminum is a fairly machinable material that can be processed with a waterjet cutter, bandsaw, fiber laser cutter, mill, lathe, and/or welding machine. Compared to most plastics and wood, aluminum is very strong; consider using aluminum for parts where strength is more important than weight. Aluminum is fairly soft, so do not design parts that require threads to be cut into aluminum; instead, use threaded inserts. We generally use the 6061 alloy, but others are acceptable; check with an expert before making the decision to use another alloy.
This is the material we are currently using for our thrust chamber. Otherwise, generally avoid brass as there are better and cheaper substitutes available (usually aluminum).
Jacobs Hall sells plywood in several sizes and thicknesses for laser cutting. Common thicknesses are 0.25 in and 0.125 in. It is important to note that wood is anisotropic; its material properties vary significantly according to the direction of the forces applied. Wood can be used for structural parts, but it may be better to consider Lexan and aluminum first. Jacobs plywood is often used to make non-structural jigs, holders, etc.
Lexan is extremely strong, although it will flex slightly under load. Most of our Lexan parts are produced with a waterjet cutter, although they can be milled, bored, etc. afterward if needed. We are unable to cut Lexan with lasers; if laser cutting is desired and strength is not a priority, consider using Delrin instead.
PLA is a bio-based plastic commonly used for 3D printing. It is slightly more brittle than ABS, but it can absorb more energy before failure. See the "Acrylonitrile Butadiene Styrene (ABS)" entry for a comparison of PLA with ABS. It is also more readily available than any other 3D printing materials in the Jacobs Hall Makerspace. PLA is a good candidate for parts with complex geometry that are non-structural in nature. It is important to note that printed parts, like wood, are anisotropic; they fail much more easily in some directions (along layer lines) than others.
ESRA guidelines say we pretty much can't use stainless steel for anything important. That being said, other projects or non-critical parts might be allowed to use stainless steel; check the regulations! Many low-strength fasteners are made out of 18-8 stainless.
One of the most common ways to produce low-cost, quick-turnaround parts out of thermoplastics.
The term "3D printing" is most often used to refer to fused deposition modeling, or FDM. There are other less common / more expensive methods of 3D printing (stereolithography and selective laser sintering), but those will not be covered in this guide. Generally, all of these processes fall under the umbrella of "additive manufacturing". Here is a description of the FDM process from Wikipedia:
Filament is fed from a large coil through a moving, heated printer extruder head, and is deposited on the growing work. The print head is moved under computer control to define the printed shape. Usually the head moves in two dimensions to deposit one horizontal plane, or layer, at a time; the work or the print head is then moved vertically by a small amount to begin a new layer.
To illustrate the basics, here are some graphics:
While 3D printers can attempt most kinds of geometry, you will achieve far more success by considering the printability of your part during the design process. In addition, some parts are simply infeasible to print.
We recommend adding 0.010" - 0.020" or 0.3 - 0.5 mm of clearance between parts that you would like to fit together. Some printers extrude more than others, making this often an iterative process.
Printed parts are anisotropic, meaning they have different properties along different directions. This is a direct consequence of the fact that they are built up layer-by-layer.
Printers generally have different resolutions in different axes. Usually, the x-y resolution is far greater than the z-resolution; after all, the z-resolution is limited by the height of each layer.
Do not attempt to use a standard FEA simulation for anything more than a broad evaluation of a printed part. Printed parts almost always fail along layer lines (i.e. one layer separates from the next one up) and not within a layer. As a result, printed parts are often much weaker than expected in in the z (normal to layers) axis and with respect to bending moments in all directions.
This step is highly machine-dependent.
Most parts require some sort of post-processing.
Removal of supports is an exceedingly common task, but also a frequent source of injury. Here are some tips.
If you cannot find a deburring tool (STAR generally has one, as does Jacobs), you may use a knife as a last resort. We recommend using a 2-3 in-long folding or fixed-blade (where legal) knife with a locking blade. In the absence of a locking blade, a swiss army-style knife is acceptable. We strongly advise against using an X-Acto knife for this purpose, even though they are commonly found in maker spaces.
When using a knife to clean up a part, always CUT AWAY FROM YOURSELF AND OTHERS.
Use long, smooth strokes and do not attempt to force the blade. If the blade becomes stuck, just back out and try again with a more gentle angle/less pressure. Try to limit the use of a knife as a prybar; use pliers when possible. Again, CUT AWAY FROM YOURSELF AND OTHERS.
The advantage of printed parts is that it is usually possible to rapidly iterate on them to fix fit issues. That being said, it is often useful to remove a small amount of material to allow two parts to fit together. We recomend the use of files, not sandpaper whenever possible. Files will remove material far more quickly, at the cost of some flexibility.
While it may seem possible to sand down printed parts to achieve a smooth finish, this is almost always a colossal waste of everyone's time. Only do so if absolutely critical. Be warned that the plastic will likely appear to whiten a bit as the sanding abrades the surface.
You may use a thin, clear epoxy to coat parts for protection and aesthetics. We recommend using a disposable foam brush and an epoxy with a long enough working time that it does not get sticky while being applied. This method may also work together with sanding (see above).
We recommend using your hands or needle-nosed pliers for the removal of supports. Do not use any sort of blade if at all possible. However, if you need to remove a brim or clean up a burr, we highly recommend the use of a . These are fairly safe and extremely effective; use by gently pulling the tool toward yourself.
If you have an ABS part, it is possible to smooth the surface using acetone vapors. . Do NOT follow a tutorial making use of a hot plate, stove, etc; this is unnecessary and dangerous, risking a safety incident to save an hour or two. Without heat, this is generally a safe process. Be warned that the acetone vapors may compromise the structural integrity of your part over time; watch for cracks and increased brittleness. There are no reasonably safe solvents that can smooth PLA parts; the only such chemicals are designed to attack organic matter and are thus highly toxic to humans. Do not attempt to acquire them.
ABS
PLA
ABS printers at Jacobs have soluble supports
Usually not available with soluble supports at Jacobs
Much higher tendency to warp, especially without enclosed, heated build envelope
Doesn't warp nearly as much
ABS printers at Jacobs are much higher resolution than the Type A / Ultimaker
Type A prints are typically the worst quality achievable, Ultimakers are slightly better
Parts may bend instead of breaking, higher elongation at break
May crack if dropped, rather than bending, but higher tensile strength
Dimensions and Fortus are limited and often in use, may require joining a lengthy queue
Type A and Ultimakers are more plentiful and more frequently free, with low turnaround time
Free at Jacobs
Fumes may give you cancer, kills the planet
Food-safe, biodegradable (with 6 months in a specialized composting facility, don't worry)
Gets softer at slightly lower temperatures
Requires Jacobs hands-on training
On-line training only needed
Little ABS personally owned by team members
In-stock at homes of team members for printing
Costs at least at Jacobs; parts are free
Glass transition at a slightly higher temperature (~ higher)
The FabLight is a laser cutter designed to safely cut both metal sheets and tubes.
For more information about the process of using the FabLight (e.g., preparing and loading a file/CAD drawing) and a full list of approved materials, please visit the Jacobs bCourses page. In a non-COVID year, both the online quiz and in-person training is required prior to being able to use the FabLight.
The FabLight is more precise than a water jet and has a less steep learning curve. In a non-COVID year, it is also more available due to being located in the general all-purpose makerspaces (studios 110 and 120) and not the metal shop with its more limited hours. For Jacobs Project Support during COVID, the FabLight similarly has a faster turnaround time and can produce parts more quickly once a request is received.
The disadvantage is that the FabLight of course cannot cut through as thick materials as a water jet. The maximum thickness that a STAR member has previously cut through on the FabLight without issue is 1/8" stainless steel.
November 2020: The Payload subteam successfully laser cut leaf springs for the Bear Force One payload structure out of 1/32" 6061 aluminum, available through the Jacobs Material store.
This manufacturing guide takes you step-by-step from a SolidWorks model to a laser cut part.
Laser cutting is a fast manufacturing and prototyping method suitable for highly planar parts.
Start by opening the SolidWorks part you want to laser cut.
Select the surface that you want the laser cutter to follow by clicking on the surface, as shown in the image below.
In the top menu, go to "File">"Save As"
From the file type drop down box, you must select a DXF (.dxf) file
Click "Yes", and a properties box will appear on the left sidebar. The selected face should be automatically filled in the "Entities to Export" box. Click the check mark and then "Save" to proceed.
We are now done with SolidWorks, but before exiting the program please take note of the dimension units of the part. In the part above, it is in inches (IPS)
Now open Adobe Illustrator, click on "File">"Open" and select your .dxf file.
A very important window will pop up. Under "Artwork Scale" you must select "Scale By: 100%" the "Scale" box must be 1.
Now, remembering what your part dimension units were, you must select the correct units you used in SolidWorks in the "Unit(s)" box. For IPS, select "Inches" from the drop down and for MMGS select "Millimeters".
After selecting the unit, the value of the "Unit(s)" box may change. This value must be set to 1.
Have you ensured that your DXF scale options are correct? It is difficult to guess whether your part has been correctly scaled or not after these options have been set.
You are now ready to proceed with processing the illustrator file.
Delete any text that SolidWorks may have generated (ie. "SolidWorks Educational Product. For instructional use only)
Select all of the lines and set the stroke width to 0.001in and color to pure red. (These steps are detailed further on in this guide)
You have now successfully prepared a SolidWorks part to be laser cut. Follow the rest of this guide for further instructions.
Flip the lever on the wall next to the laser cutter before operation (You should hear air start blowing)
Make sure there is not something hidden in the background that doesn't immediately show up on illustrator
Ensure that everything in illustrator is a vector
Lift the hood and check where the laser is pointing to confirm where exactly you are cutting
Check the extremes of the shape being cut on the material you are cutting
Try to avoid using warped materials
Jacobs Hall;
Three Universal VLS 6.60 (left) Located in 110c. and one Universal ILS 12.75 (right) Located in 120.
Invention Lab;
One VLS2.30 Located at the Citris Invention Lab.
Cory Student Workshop;
One PLS4.75 Located at the CSW.
In this course you will learn how to use the Universal Laser cutters to cut, score, and/or engrave a variety of materials. Laser cutting works by directing a high-power laser through optics onto a material which either cuts through or etches, depending on settings used. It is useful for precisely cutting 2D geometries and engraving images onto materials. Completion of this class will allow you to sign up for the Hands-On check out at Jacobs Hall. Once that step is completed, you will have access to the Universal lasers in Jacobs Hall, the Invention Lab, and the Cory Student Workshop.
Laser cutters are only operable while Design Specialists, or Student Supervisors with training are present.
Remember the buddy system- there must be a second person within earshot of you while working on the laser. Buddy system requirement will be a superuser requirement for CSW.
Any operation of the laser system is a potential fire hazard.
Most, if not all, materials are combustible in certain circumstances. Acrylic is especially flammable when vector cutting. Wood, paper, and plastics can all combust. NEVER OPERATE THE LASER SYSTEM WITHOUT CONSTANT SUPERVISION OF THE CUTTING AND ENGRAVING PROCESS. Exposure to the laser beam may cause ignition of combustible materials which can lead to a fire.
Any fire lasting more than half a second must be controlled. This list of steps begins with the simplest and escalates. Follow as many steps as necessary to extinguish any fire:
Lift the top door. This often stops small flames.
Turn off the exhaust system.
Blow on the material.
Remove the material if it is safe to grab a corner.
Spray water with spray bottle. Blue spray bottles are kept near each laser system.
If the fire is unmanageable, use the nearest fire alarm to contact the local fire department and evacuate the building.
Notify a technician immediately, even if a fire is small and easily extinguished. It’s important to know why it occurred, assess any damage, and prevent it from repeating. Discontinue using the laser until a technician has assessed that it is okay to resume.
Circumstances that can cause fire:
Files with lots of dense geometry very close together. This can cause the laser to repeatedly cut the same area, build up heat in one area and ignite it
Similarly, power settings too high for the material being cut and/or speed settings too slow
The laser is not focused properly (focus carriage is too close or too far from material). The laser is usually set up to focus automatically based on the thickness entered by the user but it can be disabled manually. Ask a Design Specialist to assist with this.
Attempting to cut materials on top of each other
Always remove all material including scrap material from the machine after use. Cordless vacuums are kept near the laser system. It is required to remove the cutting table and vacuum out the interior. Scrap material left in the laser system including materials that collect in the removable cutting table can be a fire hazard.
Exposure to the laser beam may cause physical burns and can cause severe eye damage. Proper use and care of this system are essential to safe operation.
Properly using the installed fume exhaust system is mandatory when operating the laser system. Fumes and smoke from the engraving process must be extracted from the laser system and filtered or exhausted outside.
Some materials, when engraved or cut with a laser, can produce toxic and corrosive fumes. If you are not sure of a material is laser-safe, you can consult with shop staff. We recommend that you obtain the material’s Safety Data Sheet (SDS) from the manufacturer of every material you intend to process in the laser system. The SDS discloses all of the hazards when handling or processing a particular material. Do not process any material that causes chemical deterioration of the laser system such as rust, metal etching or pitting, peeling paint, etc.
The Invention Lab lasers are on a first-come basis. Please be kind to your fellow users and be accommodating if you have a very long job.
For the Jacobs Hall lasers, the reservation system can be found at http://reserve.jacobshall.org/ (Links to an external site.)Links to an external site.. Please prepare your cut file in advance and estimate the cutting time using the Universal Laser software. See the Laser Cutter Interface section below regarding estimating cutting time.
Reservations can be made up to 7 days in advance.
Late & no-shows: After 10 minutes a reservation is forfeited and the remainder of the time is given to the first drop-in user. If you cannot make it to an appointment, please cancel it before it begins.
Unreserved times are designated drop-in use by anyone until the next reservation.
For the CSW, access requires the presence of superuser on first come first serve basis by checking shop calendar for superuser availability. Limiting access for maker-pass users for fairness to non-maker-pass users.
If a laser system breaks or is damaged while you are using it, inform the shop staff. Equipment damage is a normal part of the shop environment; for safety reasons it is important to inform a shop staff member immediately.
Always clean up fully after yourself. No material scraps should remain in the shop or in the machines.
If a laser system is not cutting material, the lens may need to be cleaned. Do not increase the intensity as this can cause the lens to burst. Notify a shop staff member and the lens can be cleaned if needed.
For your health safety and others in the shop, processing any material that is not laser-safe is against shop policy. Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
PVC (aka Polyvinyl chloride, vinyl, pleather) is not laser safe. Chlorinated materials ( are corrosive to the machine and toxic
Chlorinated rubbers also release chlorine. Some paints contain chlorinated rubber.
Nitrile rubber releases hydrogen cyanide when combusted
Polystyrene foam (aka Styrofoam) - Melts and catches fire. Very dangerous.
Almost any foam - Including Foam core, polypropylene foam, etc. Very dangerous.
Construction grade plywood - Most plywood sold in hardware stores is not bonded with modified adhesives making it prone to smoking, flaming, charring at the edges and producing toxic fumes (Best Plywood for Laser Cutting (Links to an external site.)Links to an external site.: No Knots, Thicker/Less Ply, Interior Grade, urea-formaldehyde(UF) or melamine-formaldehyde(off-gasses less formaldehyde) glue (Links to an external site.)Links to an external site.)
ABS off-gases hydrogen cyanide in fumes, a chemical known to be very toxic and has been used as a chemical warfare agent.
Polycarbonate (aka Lexan) - absorbs infrared radiation, causing it to melt and warp. Looks very similar to acrylic sheets.
Remember that all materials create fumes when laser cut. "Safe" materials are judged as such by not being overly combustible or releasing corrosive, mutagenic, or poisonous gases when laser cut.Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
Paper / Cardstock - can be both etched and cut
Wood - can be both etched and cut
Cast Acrylic can be cut or rastered (has a frosted, translucent appearance)
Extruded Acrylic - can be cut (does not frost when etched)
Delrin - hard plastic, good for mechanical parts like gears (available in different hardnesses)
Cotton / Felt / Hemp - cuts well, engraves well
Polyester fabric - cuts okay, edges melt a bit, doesn’t engrave well
Leather - natural leather only, not synthetic “pleather”
Anodized Aluminum - can be etched (Black anodized aluminum provides best contrast out of all anodized aluminum)
Ceramic / Stone - Engraving is possible on porcelain, ceramic, terracotta slate, marble and stone
Brass - Uncoated brass can not be etched with a laser, it needs to have some kind of coating (such as paint).
Glass - Can be etched only. Must be flat. Etching colored glass has best visual results.
Rubber - Buna-N Rubber, Polyurethane rubber, natural rubber (no nitrile rubber or any chlorine-containing rubber)
Step 0 - File Setup
Files can be set up ahead of time to use time efficiently. Universal laser systems operate in one of two modes. A raster mode, in which images are marked or engraved into a material by etching a pattern of dots into the material at high resolutions up to 1000 dpi, and a vector mode in which the laser follows a two dimensional path to cut or mark a shape into a material. The printer driver determines whether an element in the graphic data being printed is a vector or raster object by its width.
The 3 laser cutters in 110C can cut 32" wide by 18" high, and the laser cutter in 120 can cut 48" wide by 24" high. The CSW laser cutter bed size is 18"x24". If you want to cut using the full cut area, set up the file you want to cut using 24", 32" or 48" for the width, and 18" or 24" for the height. Also select color mode RGB. This is crucial because the laser cutter software will not understand other modes.
Line thickness
Only lines and curves with a thickness of .001 in (.072 pt) or less will be interpreted as vector objects. All other elements of the graphic, including JPEG images, being printed will be interpreted as raster objects. In order to print vector elements, the software you are printing from must support creation of lines with a thickness of .001 in (.072 pt) or less. This includes Adobe Illustrator, Rhino, SolidWorks, AutoCAD, and other drafting software.
Line Color
Red lines indicate a line to be cut, Blue lines indicate a line to be scored, Black lines indicate a line to be engraved. When changing colors in Illustrator, use the following instructions to make sure you are using true RGB values;
1. To change line color, make sure your image is selected, then click on the color pallet icon in the tool bar;
2. Click on the "more" dropdown icon in the upper right of the colors box to choose "Show Options". Make sure RGB is also selected;
3. To make a cut or score line Make sure that the color choice is for "stroke" by clicking on the stroke square (which looks like a hollow red rectangle in the below icon). Now enter the correct values for the type of operation you want. For instance, To make a cut line enter 255 in the R setting, 0 in the G setting, and 0 in the B setting. To make a score line enter 0 in the R setting, 0 in the green setting, and 255 in the blue setting.
Step 1 - Clean off honeycomb cutting bed. Debris can be a fire hazard.
Step 2 - Load and Position Material
*When in the Invention Lab, open the ventilation gate located on the wall behind and to the right of the machine
Open the top door to the laser system and place material to be laser processed onto the engraving table. You may need to manually move the support table down to allow clearance to fit thicker materials into the machine. The material must be flat and consistent in thickness. The machine cannot remain focused on warped materials or materials that change in thickness/height.
*When at the CSW, turn the machine on in the correct order;
1.Press the power button on BOFA fume extractor
2. Turn the air compressor 90 degrees counterclockwise
3. Turn on the Laser Cutter
Step 3 - Sending to Universal Control Panel
Have you ensured that your illustrator file is the correct scale? If you do not know the scale, press Ctrl-R to bring up the rulers. See if your part is reasonably sized.
While still in Illustrator, click Print to open the printing options.
Click "set up" in the bottom, right corner
Open the preferences dialog. This will load the laser cutter's material settings database.
Laser Cutter Interface
Vector cutting depth and raster engraving depth (or marking intensity if you are surface marking only) are controlled by specifying the speed of processing and the laser power level for raster engraving and by specifying the speed of processing, laser power level and number of pulses per inch (PPI) for vector cutting and marking.
Materials are listed under various categories. Under the appropriate category or sub-category, select the material you are processing.
Enter the material thickness. Use calipers to measure the thickness accurately.
Click Defaults to reset the Intensity Adjustment sliders to 0%. Only adjust vector cutting intensity if needed.
Click OK, then click Print.
At the bottom right of the screen, click the Universal Control Panel icon.
Make sure the material is positioned correctly within the engraving area, and the geometry is positioned correctly in the Control Panel.
Close the top door.
Check that the fume exhaust is running and compressed air is flowing. Controls for each of these should be labeled near the laser.
Always ask a Design Specialist if you have any issues setting up your cut file or preparing the laser cutter.
Press the green START button on the UCP to begin laser processing.
The Universal software should be set to automatically focus based on the material thickness specified.
Order of execution when using the materials database tab proceeds with raster objects first, then vector marking objects and finally vector cutting objects.
It is not guaranteed that the laser will successfully cut through a material. It’s recommended to do a quick test cut:
Create a very small shape (such as a ½" - ¾” diameter circle) and position it in a marginal part of your material or another piece of the same material.
Cut the test geometry. As always, watch for anything
On the UCP, click “Settings” to re-open cut settings.
Adjust the intensity sliders on the top right but increase by small increments.
Then move the test cut shape in order to repeat.
Universal Laser Systems Safety and Operation Reference
Jacobs Hall;
Three Universal VLS 6.60 (left) Located in 110c. and one Universal ILS 12.75 (right) Located in 120.
Invention Lab;
One VLS2.30 Located at the Citris Invention Lab.
Cory Student Workshop;
One PLS4.75 Located at the CSW.
Course Synopsis
In this course you will learn how to use the Universal Laser cutters to cut, score, and/or engrave a variety of materials. Laser cutting works by directing a high-power laser through optics onto a material which either cuts through or etches, depending on settings used. It is useful for precisely cutting 2D geometries and engraving images onto materials. Completion of this class will allow you to sign up for the Hands-On check out at Jacobs Hall. Once that step is completed, you will have access to the Universal lasers in Jacobs Hall, the Invention Lab, and the Cory Student Workshop.
Laser Safety and Procedures
Laser cutters are only operable while Design Specialists, or Student Supervisors with training are present.
Remember the buddy system- there must be a second person within earshot of you while working on the laser. Buddy system requirement will be a superuser requirement for CSW.
Any operation of the laser system is a potential fire hazard.
Most, if not all, materials are combustible in certain circumstances. Acrylic is especially flammable when vector cutting. Wood, paper, and plastics can all combust. NEVER OPERATE THE LASER SYSTEM WITHOUT CONSTANT SUPERVISION OF THE CUTTING AND ENGRAVING PROCESS. Exposure to the laser beam may cause ignition of combustible materials which can lead to a fire.
Fire Protocol
Any fire lasting more than half a second must be controlled. This list of steps begins with the simplest and escalates. Follow as many steps as necessary to extinguish any fire:
Lift the top door. This often stops small flames.
Turn off the exhaust system.
Blow on the material.
Remove the material if it is safe to grab a corner.
Spray water with spray bottle. Blue spray bottles are kept near each laser system.
If the fire is unmanageable, use the nearest fire alarm to contact the local fire department and evacuate the building.
Notify a technician immediately, even if a fire is small and easily extinguished. It’s important to know why it occurred, assess any damage, and prevent it from repeating. Discontinue using the laser until a technician has assessed that it is okay to resume.
Circumstances that can cause fire:
Files with lots of dense geometry very close together. This can cause the laser to repeatedly cut the same area, build up heat in one area and ignite it
Similarly, power settings too high for the material being cut and/or speed settings too slow
The laser is not focused properly (focus carriage is too close or too far from material). The laser is usually set up to focus automatically based on the thickness entered by the user but it can be disabled manually. Ask a Design Specialist to assist with this.
Attempting to cut materials on top of each other
Always remove all material including scrap material from the machine after use. Cordless vacuums are kept near the laser system. It is required to remove the cutting table and vacuum out the interior. Scrap material left in the laser system including materials that collect in the removable cutting table can be a fire hazard.
Exposure to the laser beam may cause physical burns and can cause severe eye damage. Proper use and care of this system are essential to safe operation.
Properly using the installed fume exhaust system is mandatory when operating the laser system. Fumes and smoke from the engraving process must be extracted from the laser system and filtered or exhausted outside.
Some materials, when engraved or cut with a laser, can produce toxic and corrosive fumes. If you are not sure of a material is laser-safe, you can consult with shop staff. We recommend that you obtain the material’s Safety Data Sheet (SDS) from the manufacturer of every material you intend to process in the laser system. The SDS discloses all of the hazards when handling or processing a particular material. Do not process any material that causes chemical deterioration of the laser system such as rust, metal etching or pitting, peeling paint, etc.
Appointment Reservation System
The Invention Lab lasers are on a first-come basis. Please be kind to your fellow users and be accommodating if you have a very long job.
For the Jacobs Hall lasers, the reservation system can be found at http://reserve.jacobshall.org/ (Links to an external site.)Links to an external site.. Please prepare your cut file in advance and estimate the cutting time using the Universal Laser software. See the Laser Cutter Interface section below regarding estimating cutting time.
Reservations can be made up to 7 days in advance.
Late & no-shows: After 10 minutes a reservation is forfeited and the remainder of the time is given to the first drop-in user. If you cannot make it to an appointment, please cancel it before it begins.
Unreserved times are designated drop-in use by anyone until the next reservation.
For the CSW, access requires the presence of superuser on first come first serve basis by checking shop calendar for superuser availability. Limiting access for maker-pass users for fairness to non-maker-pass users.
Laser Work Space Etiquette
If a laser system breaks or is damaged while you are using it, inform the shop staff. Equipment damage is a normal part of the shop environment; for safety reasons it is important to inform a shop staff member immediately.
Always clean up fully after yourself. No material scraps should remain in the shop or in the machines.
If a laser system is not cutting material, the lens may need to be cleaned. Do not increase the intensity as this can cause the lens to burst. Notify a shop staff member and the lens can be cleaned if needed.
BANNED Materials
For your health safety and others in the shop, processing any material that is not laser-safe is against shop policy. Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
PVC (aka Polyvinyl chloride, vinyl, pleather) is not laser safe. Chlorinated materials ( are corrosive to the machine and toxic
Chlorinated rubbers also release chlorine. Some paints contain chlorinated rubber.
Nitrile rubber releases hydrogen cyanide when combusted
Polystyrene foam (aka Styrofoam) - Melts and catches fire. Very dangerous.
Almost any foam - Including Foam core, polypropylene foam, etc. Very dangerous.
Construction grade plywood - Most plywood sold in hardware stores is not bonded with modified adhesives making it prone to smoking, flaming, charring at the edges and producing toxic fumes (Best Plywood for Laser Cutting (Links to an external site.)Links to an external site.: No Knots, Thicker/Less Ply, Interior Grade, urea-formaldehyde(UF) or melamine-formaldehyde(off-gasses less formaldehyde) glue (Links to an external site.)Links to an external site.)
ABS off-gases hydrogen cyanide in fumes, a chemical known to be very toxic and has been used as a chemical warfare agent.
Polycarbonate (aka Lexan) - absorbs infrared radiation, causing it to melt and warp. Looks very similar to acrylic sheets.
Laser safe materials
Remember that all materials create fumes when laser cut. "Safe" materials are judged as such by not being overly combustible or releasing corrosive, mutagenic, or poisonous gases when laser cut.Always check with a technician before assuming any material NOT purchased at the Jacobs Online store is okay.
Paper / Cardstock - can be both etched and cut
Wood - can be both etched and cut
Cast Acrylic can be cut or rastered (has a frosted, translucent appearance)
Extruded Acrylic - can be cut (does not frost when etched)
Delrin - hard plastic, good for mechanical parts like gears (available in different hardnesses)
Cotton / Felt / Hemp - cuts well, engraves well
Polyester fabric - cuts okay, edges melt a bit, doesn’t engrave well
Leather - natural leather only, not synthetic “pleather”
Anodized Aluminum - can be etched (Black anodized aluminum provides best contrast out of all anodized aluminum)
Ceramic / Stone - Engraving is possible on porcelain, ceramic, terracotta slate, marble and stone
Brass - Uncoated brass can not be etched with a laser, it needs to have some kind of coating (such as paint).
Glass - Can be etched only. Must be flat. Etching colored glass has best visual results.
Rubber - Buna-N Rubber, Polyurethane rubber, natural rubber (no nitrile rubber or any chlorine-containing rubber)
Step 0 - File Setup
Files can be set up ahead of time to use time efficiently. Universal laser systems operate in one of two modes. A raster mode, in which images are marked or engraved into a material by etching a pattern of dots into the material at high resolutions up to 1000 dpi, and a vector mode in which the laser follows a two dimensional path to cut or mark a shape into a material. The printer driver determines whether an element in the graphic data being printed is a vector or raster object by its width.
The 3 laser cutters in 110C can cut 32" wide by 18" high, and the laser cutter in 120 can cut 48" wide by 24" high. The CSW laser cutter bed size is 18"x24". If you want to cut using the full cut area, set up the file you want to cut using 24", 32" or 48" for the width, and 18" or 24" for the height. Also select color mode RGB. This is crucial because the laser cutter software will not understand other modes.
File Requirements
Line thickness
Only lines and curves with a thickness of .001 in (.072 pt) or less will be interpreted as vector objects. All other elements of the graphic, including JPEG images, being printed will be interpreted as raster objects. In order to print vector elements, the software you are printing from must support creation of lines with a thickness of .001 in (.072 pt) or less. This includes Adobe Illustrator, Rhino, SolidWorks, AutoCAD, and other drafting software.
Line Color
Red lines indicate a line to be cut, Blue lines indicate a line to be scored, Black lines indicate a line to be engraved. When changing colors in Illustrator, use the following instructions to make sure you are using true RGB values;
1. To change line color, make sure your image is selected, then click on the color pallet icon in the tool bar;
2. Click on the "more" dropdown icon in the upper right of the colors box to choose "Show Options". Make sure RGB is also selected;
3. To make a cut or score line Make sure that the color choice is for "stroke" by clicking on the stroke square (which looks like a hollow red rectangle in the below icon). Now enter the correct values for the type of operation you want. For instance, To make a cut line enter 255 in the R setting, 0 in the G setting, and 0 in the B setting. To make a score line enter 0 in the R setting, 0 in the green setting, and 255 in the blue setting.
Laser System
Step 1 - Clean off honeycomb cutting bed. Debris can be a fire hazard.
Step 2 - Load and Position Material
*When in the Invention Lab, open the ventilation gate located on the wall behind and to the right of the machine
Open the top door to the laser system and place material to be laser processed onto the engraving table. You may need to manually move the support table down to allow clearance to fit thicker materials into the machine. The material must be flat and consistent in thickness. The machine cannot remain focused on warped materials or materials that change in thickness/height.
*When at the CSW, turn the machine on inthe correct order;
1.Press the power button on BOFA fume extractor
2. Turn the air compressor 90 degrees counterclockwise
3. Turn on the Laser Cutter
Step 3 - Sending to Universal Control Panel
While still in Illustrator, click Print to open the printing options.
Click "set up" in the bottom, right corner
Open the preferences dialog. This will load the laser cutter's material settings database.
Laser Cutter Interface
Vector cutting depth and raster engraving depth (or marking intensity if you are surface marking only) are controlled by specifying the speed of processing and the laser power level for raster engraving and by specifying the speed of processing, laser power level and number of pulses per inch (PPI) for vector cutting and marking.
Materials are listed under various categories. Under the appropriate category or sub-category, select the material you are processing.
Enter the material thickness. Use calipers to measure the thickness accurately.
Click Defaults to reset the Intensity Adjustment sliders to 0%. Only adjust vector cutting intensity if needed.
Click OK, then click Print.
At the bottom right of the screen, click the Universal Control Panel icon.
Before Starting The Laser Cutter
Make sure the material is positioned correctly within the engraving area, and the geometry is positioned correctly in the Control Panel.
Close the top door.
Check that the fume exhaust is running and compressed air is flowing. Controls for each of these should be labeled near the laser.
Always ask a Design Specialist if you have any issues setting up your cut file or preparing the laser cutter.
Press the green START button on the UCP to begin laser processing.
The Universal software should be set to automatically focus based on the material thickness specified.
Order of execution when using the materials database tab proceeds with raster objects first, then vector marking objects and finally vector cutting objects.
Test Cuts First
It is not guaranteed that the laser will successfully cut through a material. It’s recommended to do a quick test cut:
Create a very small shape (such as a ½" - ¾” diameter circle) and position it in a marginal part of your material or another piece of the same material.
Cut the test geometry. As always, watch for anything
On the UCP, click “Settings” to re-open cut settings.
Adjust the intensity sliders on the top right but increase by small increments.
Then move the test cut shape in order to repeat.
Most people use it to mill PCBs but that's boring
The Othermill creates very dimensionally accurate parts, but may be slower and more complex than other prototyping processes. If your part significantly depends on being diemnsionally accurate (for example, low backlash gears), then the othermill may be a good choice. Laser cutters produce a noticeable and uneven kerf, and 3D printing (FDM) cannot produce very fine details well.
The smallest commonly available Othermill bit that can be used to mill out parts is the 1/32" bit. This bit can cut up to materials that are 0.125" thick. Be aware that machining speed can be significantly slowed down the smaller the bit size is. Refer to online resources on Computer-Aided Machining (CAM) best practices on what bit to choose.
In order of machinability, here are the materials the authors have used successfully on the Othermill:
Delrin (acetyl homopolymer resin)
Lexan (polycarbonate)
Aluminum
The Othermill should not be used to cut steel.
Download the Jacobs Hall tool library from the Jacobs Hall bcourses training for the Othermill. Do not download the tool library directly from Bantam Tools, as it contains some inaccuracies.
Measure the stock and CAD the part to be no greater than the thickness of the stock. If the part is mostly flat, have its thickness match the thickness of the stock unless facing is needed.
Set up the Work Coordinate System as follows. Other tutorials may recommend you set the origin at the top of the stock, but this can cause poor results and collisions with the spoilboard. While these toolpaths will be offset in the Z direction when we import them into the Bantam Tools software, we will correct this at a later time.
Input the accurate dimensions of your stock in the Stock tab. Then, adjust the position of your part relative to the edges of the stock. Items in red boxes should generally be changed for each part or stock piece, while the rest should match the image.
The term "feeds and speeds" refers to how quickly the tool rotates and how quickly it moves along the x, y, and z axis. Smaller tools should generally be used with slower feeds and speeds.
Aluminum is significantly tougher than plastics. most important is the stepdown on operations with multiple depths; use a stepdown of at most 0.004". For drilling, use a very conservative chip clearing toolpath, pecking in 0.001" increments at a speed of 0.5 in/min. Milling aluminum with the Othermill is somewhat of an acquired skill, so don't worry if you break a bit or two at first. Do not attempt to mill aluminum with anything smaller than a 1/16" endmill.
Climb milling will result in a better finish and longer tool life.
Check the "keep tool down" checkbox or cuts with multiple depths will lift the tool each time.
Always keep the Ramp checkbox checked and generally use a ramp angle of 3-5 degrees depending on the material (larger angle ok on softer materials).
Facing
Bore
2D Contour
Always simulate your toolpaths in Fusion before exporting them for use on the machine. This is the primary way to prevent damage to the machine, the tooling, and the part
Open the simulation settings and check the "Stock" box. You can change from the default green color by changing the material options, but this is not important. Watch the entire simulation; if it is long, speed it up as little as necessary to ensure you catch any unintended behavior.
Right click on each operation on the left dropdown and select "Post Process". Select the settings for the Othermill and give your toolpath a descriptive name and number: e.g. 1_facing, 2_bore, etc. Numbering will help you keep track of the order in which to run each operation.
This step will produce .gcode files; these are text files containing a list of instructions that will be fed to the Othermill during operation. Make sure you save the gcode files in an accessible location on your filesystem.
Turn on the Othermill using the power switch at the back left corner.
Ensure that the emergency stop (big red button) is not engaged.
Connect the machine to a computer that has Bantam Tools installed.
Open Bantam Tools, and home the machine.
If using the fixturing bracket, locate the bracket by pressing "locate".
Insert a 1/8" endmill upside down (with the cutting flute inside the collet).
Load the material (tbd)
Load the toolpaths. Click the "Open Files" button and select your .gcode files.
Offset the toolpaths. If you do not perform this step, nothing will be milled. For each toolpath, open the "Placement" dropdown and enter -[stock thickness] under the z-offset. For exampele, if I have a sheet of nominally 1/8" Delrin that I have measured to be 0.135" thick, I would put "-0.130 in". You may also add x and y offsets, but be sure to repeat the process for each individual operation / toolpath.
Load a tool by clicking "Change...". Mount the desired bit and select it from the drop down menu. Click "Locate" and ensure that the mill has moved the bit above a clear section of the spoilboard (metal bed). If not, manually adjust. Confirm the position, and the machine will begin to move the bit down to touch the bed. While this is happening, make sure you are ready to stop the machine (press "ESC" or the emergency stop to stop). Once the bit has made contact with the bed, the machine should immediately stop trying to move the bit down. If you head any sound of resistance STOP THE MILL and try again.
A way to selectively remove material from a piece of stock
Contrary to popular belief, a mill is not a drill press. This is a manual mill:
A mill has a spindle which holds an end mill. End mills are similar in appearance to drill bits, but are not the same!
The spindle spins the end mill rapidly while the material (or the spindle) is moved in the x, y, or z directions. More advanced, usually computer numerical control (CNC) machines can also sometimes rotate, giving up to 4 or 5 "axes" to move in. With CNC milling, a computer, rather than a human machinist, handles the motion of the stock and spindle. Here is an example of a CNC mill in action:
Both manual mills and CNC mills generally share some basics in terms of how they operate. Here is a video that covers the basics of mills:
Just like drill presses, mills can make holes in materials. You can either use an end mill, or simply put a standard drill bit in the mill using a removable chuck. Mills are particularly useful if you would like a set of very precisely spaced holes, as they possess an x-y coordinate system (drill presses generally do not).
In the image above, notice that the center hole is not bored all the way through. This is generally possible to do fairly accurately even on a manual mill, with the use of a stop. However, dimensional accuracy may vary. Always check with your machinist first.
In the US, drills come in number sizes (smallest useful size being #50-#60 and going all the way up to #1, which is roughly 0.228 in) as well as letter sizes, which start at A (0.234 in) up to Z (0.413). Beyond and interspersed with the letter and number drills are standard fractional inch size, ranging commonly from as small as 3/64 in up to 1 1/2 in. Check with your machinist to see what sizes are available first.
A mill can remove material from a face or create a flat surface at any depth. Furthermore, sharp corners are possible if the tool is allowed to travel off the end of the part (see Pockets section for examples of when this is not the case). It is best if these cuts are at right angles to each other; more complex geometry will require the use of CNC.
For an example video of a CNC machine cutting a more complex profile, see below:
When a flat surface with some type of wall on the sides is desired, we have a pocket. Mills are able to do pockets, but keep a few things in mind:
End mills (the tool) have finite radii. For example, if an 1/8" diameter end mill is used to make a pocket, the interior corners will have a minimum 1/16" radius. Use a fillet in CAD to reflect this.
Conventional (manual) mills may not easily be able to make, for example, a rectangular pocket with precise corner coordinates, especially if the pocket is deep and requires multiple passes. This type of geometry is better suited for a function mill or a CNC mill. When in doubt, check what can and cannot be done with the person who will be making the part!
This type of geometry will generally only be possible with a CNC mill. Please be aware that CNC parts can have long lead times if coming from the machine shop. Furthermore, there are still limitations on what a CNC machine can do; as with manual mills, there are limits based on available tooling (curved surfaces generally require ball end mills) and the material.
Try to limit the number of different tools needed to make your part. Tool changes can cost significant time and effort. For example, try making all holes a standard diameter, or choose just a few. If a pocket is large, use large-radius fillets on the corners to allow the machinist to use a single large tool to make the feature in one pass, rather than switching to a smaller tool just for the corners.
When in doubt, ask. Other club members or the machine shop staff are happy to help!
Shoutout to Dennis K. Lieu
Coarse threads are the most commonly available and should be suitable for almost all use cases
Before choosing to use metric threads, please coordinate with you project team to ensure the type of thread used is consistent.
When working on a project or part, try to minimize the number of different sizes of screws used. Avoid having a variety of screw sizes.
Try to keep screw drive type consistent.
Use the clearance hole chart in the "Tolerancing" page for appropriate clearence hole sizes.
Be mindful of the size of the screw head when designing a part, especially of how the head affects clearance to other parts. It can be useful to obtain the SolidWorks model of a specific screw (commonly avaliable on McMaster) to check for clearance issues.
Screws used as a hinge, such as part of a screw-nut hinge combination, and other structural-critical screws should have an appropriate thread locker (such as Loctite 242) applied.
Screws and standoffs used in close proximity to exposed electronics should ideally be non-conductive.
Always make sure the nut you get corresponds with the thread of the screw that you are planning on using it with.
The most common type of nut that we use is a hex nut.
Nylock nuts are the common alternative if a more secure connection needs to be made.
In nearly every case, nuts require much more clearance than screws and thus are usually oriented away from moving parts and where they can't come into contact with other surfaces.
Threaded inserts can be extremely useful way of having a threaded connection in your designs.
A very common situation that can arise is a need to thread into 3D printed parts. 3D-printed parts are difficult to tap (use a tool to create threads on the inside of a hole) because plastics (especially for PLA) deform at low temperatures. 3D-printing internal threads are also difficult because of the need for high precision. Directly threading a screw into a part is often not ideal, because repeatedly removing and screwing the fastener will appreciably lower the integrity and strength of the connection.
As such, threaded inserts are an ideal solution to this issue, since the insert is designed to be permanently secured to the part yet also allow for the repeated insertion of a screw into the thread. An analogous way of achieving this is to design the part to hold a captive hex or square nut inside. In this case, the nut acts as the insert. More information about plastic-specific inserts can be found here:
Another common situation is a need for a thread into a soft metal, such as aluminum. Aluminum is often desirable, especially for aerospace applications, because of its low weight. However, it is not ideal to directly thread into aluminum for the following reasons:
Most fasteners are steel, which is considerably stronger than aluminum. A threaded interface between steel and aluminum can cause significant wear to the internal threads of the aluminum leading to issues such including binding.
For a reference on dimensions on mil-spec threaded inserts, see the below documents:
Rivets are permanently-deforming fasteners. Please do not use rivets unless you have a very good reason to do so, as they prevent the disassembly of the part (without an angle grinder). There is little information on rivets included here on purpose. Rivnuts or Nutserts are slightly better, but also have issues related to their deformation.
Here are some general tolerancing tips, picked up from work experience, in no particular order. Anyone is welcome to add to these or correct them if you see something inaccurate.
Tolerances should always be as large as possible for the part to still function
Overly tight tolerances are expensive, time consuming, and unnecessary
3D printed parts will shrink. A lot.
Online estimates are ~8% for ABS and ~3% for PLA but the actual amount will vary drastically based on the printer, settings, and the part itself.
If possible, part corners should be chamfered or filleted, especially for sharp/hard materials
For machined parts, a surface finish of 125 microinches (3.175 micrometers) is standard
Any holes to be tapped should be first made one size smaller than the tap size
I.e. for a #6 screw, one should drill a #5 hole before tapping with a #6 tap
Holes should be larger than the fasteners that go in them. The smallest diameters for a "normal" fit by ASME standards are listed below.
GD&T should be added at some point
.
*
These parameters are specified in the laser cutter preferences interface by one of two methods. The two methods are laid out in tabs in the laser cutter interface. The first method is a materials database method which simplifies setup for beginners and casual users, the second method is a manual method with allows much more control for advanced users. Each method treats assignment of laser job settings to colors in the graphic being printed and interpretation of raster and vector elements in the graphic being printed in slightly different ways.
It will load the geometry into this screen.
.
*
These parameters are specified in the laser cutter preferences interface by one of two methods. The two methods are laid out in tabs in the laser cutter interface. The first method is a materials database method which simplifies setup for beginners and casual users, the second method is a manual method with allows much more control for advanced users. Each method treats assignment of laser job settings to colors in the graphic being printed and interpretation of raster and vector elements in the graphic being printed in slightly different ways.
It will load the geometry into this screen.
When it comes to sizing holes, make sure that there is actually a drill bit or end mill with the correct diameter for your hole. Perform a google search for a drill bit sizing chart or see the table here: for a conversion between letter and number drill bits to decimal inches.
That being said, there are some parts that are great candidates for CNC and it can certainly be a useful technology. Small parts especially will be easier to make (see: ) and can make design significantly easier.
As a general rule, simple geometry is better. Things like right angles and low requirements for accuracy and precision (see: ) make everyone's lives easier.
For a more in-depth treatment, refer to this fastener handout:
If working in US customary units, refer also to the Wikipedia page on the Unified Thread Standard: If working in SI units, refer to the ISO thread sizing Wikipedia page:
can always be of concern when joining two dissimilar metals.
Again, threaded fasteners or captive nuts are ideal in this scenario. When choosing inserts for aluminum, make sure they are passivated or mil-spec, as to prevent galvanic corrosion from occurring. can be ideal for this application.
See ASME standard 18.2.8 for more information, or go to:
Designation | Nom. (in) | Nom. (mm) | Min. (in) | Min. (mm) |
#0 | 0.060 | 1.524 | 0.076 | 1.930 |
M1.6 | 0.063 | 1.600 | 0.071 | 1.800 |
#1 | 0.073 | 1.854 | 0.089 | 2.261 |
M2.0 | 0.079 | 2.000 | 0.094 | 2.400 |
#2 | 0.086 | 2.184 | 0.102 | 2.591 |
M2.5 | 0.098 | 2.500 | 0.114 | 2.900 |
#3 | 0.099 | 2.515 | 0.116 | 2.946 |
#4 | 0.112 | 2.845 | 0.128 | 3.251 |
M3.0 | 0.118 | 3.000 | 0.134 | 3.400 |
#5 | 0.125 | 3.175 | 0.156 | 3.962 |
#6 | 0.138 | 3.505 | 0.170 | 4.318 |
M4.0 | 0.157 | 4.000 | 0.177 | 4.500 |
#8 | 0.164 | 4.166 | 0.196 | 4.978 |
#10 | 0.190 | 4.826 | 0.221 | 5.613 |
M5.0 | 0.197 | 5.000 | 0.217 | 5.500 |
#12 | 0.216 | 5.486 | N/A | N/A |
M6.0 | 0.236 | 6.000 | 0.260 | 6.600 |
1/4" | 0.250 | 6.350 | 0.281 | 7.137 |
M8.0 | 0.315 | 8.000 | 0.354 | 9.000 |
A description of each of the main components which make up the airframe of a rocket.
Tubing is probably the essential airframe component as it makes up almost all of the exterior structure and shape of the rocket. Historically, we have mainly used BlueTube as our default tubing material, but we are moving towards carbon fiber for our larger rocket designs as it offers a great combination of strength and low weight.
The Payload Tube is the tube dedicated to housing the payload, whatever it may be. This is generally directly under the nose cone as the payload is often partially stored in the nose cone as well to efficiently utilize all available space.
The Avionics Bay (or Av Bay) houses all of the electrical boards, flight computers, and avionics of the rocket. As this is a very delicate section of the rocket, it is generally closed/sealed on both ends by bulkheads. It also usually has a door, sled, or other form of access so the Avionics team can access the boards at anytime time, even when the rocket is on the launch rail.
The Recovery Tube houses the parachutes (and supporting recovery components) of the rocket. This section of the rocket has to be able to separate to allow the parachutes to release after apogee has been reached. In the past this separation has been done via black powder.
The Booster Tube is at the bottom of the rocket and houses the motor. It is generally sealed off from the rest of the rocket.
Couplers are tubes that work as connecting sections of the rocket that have a slightly smaller diameter than the rocket itself, so that they can fit snugly inside of it and allow different rocket tube sections to mate. They are permanently attached to these tube sections and generally made out of the same material as the main tubing.
Bulkheads are the "dividing walls" of the rocket or in other words structural sealing tools that are fitted inside the tube and comprise the entire area of the inner tube. They are used to seal off sections of the rocket where we do not want any interaction, such as between the motor and whatever is above it. They are also used as structural mounting spots for things like parachute u-bolts. Sometimes they have holes so that pipes can pass through them. Historically, we have made these out of wood. We are planning to use acrylic for our larger rockets.
Centering rings are structural tools used to hold things in place inside of the rocket. They are similar to bulkheads except that they have a hollow center (ring instead of circle). We have used them to secure the payload in the nose cone and secure the motor tube inside of the booster tube. When used to center the motor, they should be strong enough to withstand high impulses that the motor produces during flight. Historically, we have made these out of wood. We are planning to use aluminum for our larger rockets.
The cone shaped nose of the rocket that is designed to reduce drag at the front end/top of the rocket. We generally go for nose cones that are made of carbon fiber and have a 4:1 length to diameter ratio (a 6in diameter rocket would have a 24 in length nose cone).
A custom piece of tubing that is made to facilitate a diameter transition in a rocket. For example, a transition piece was used in Arktos to transition from a 6in diameter (nose cone and payload tube) to a 4in diameter (recovery, booster, av bay). Transition pieces allow for versatility by allowing certain parts of the rocket to house larger diameters without requiring the entire rocket to commit to the larger size.
A stabilizing agent that is fitted to the bottom of the rocket.
Similar to the nose cone, but at the very end of the rocket. A tail cone exists to buffer the change at the bottom of the rocket from "whatever diameter" to nothing (i.e. where the rocket ends). Adding in a piece that gives a gradual change in diameter helps to eliminate drag and achieve a higher apogee.
A brief overview of the proper steps when manufacturing a tube using the X-Winder.
Always wear gloves when handling epoxy and composite fibers.
Keep hands, feet, hair, etc. out of the way of the X-Winder when in operation. It is a large machine and there is a good chance it could cause as much damage to you as it will to itself.
When using ovens, avoid accessing them while hot, and wear necessary safety equipment when handling hot objects.
Select the desired tow spool and epoxy. The epoxy that is used should have a setting time that is longer than the estimated wind time to avoid issues with X-Winder operation.
Ensure the X-Winder is clean and in working order: motors turn smoothly without overheating, tow spool rotates freely, belts are secured tightly, no residual epoxy, etc.
Mount the desired mandrel to the main rod, making sure that everything is tight and does not slip when rotated.
Make accurate measurements of the tow line and the mandrel, as well as the start and end lengths of the wind pattern. (Note that generally the ends of a wind are inconsistent with the bulk, so it is best to wind 2-3 in. longer than the desired tube length and then cut to size after.)
Input these measurements into the X-Winder software along with desired wind angles and layer count.
Cut a piece of bleeder/breather cloth that will fit around the mandrel for use after the wet wind.
Depending on the estimated wind time, this is a good point to think about pre-heating the curing oven to the desired temperature.
Pull the tow through the rollers to the delivery head. Be sure to place the line between all spacers and check that no fraying occurs as the tow is pulled through.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the software for part of a layer, checking for proper spacing of the wind and wind behavior at the ends of each pass. It is a good idea to check each different wind angle and verify that things look good and the X-Winder is working as intended.
If everything is good to go, cut the tow and unwrap the partial wind. Remove the mandrel to prepare it for a wet wind.
Wrap the mandrel in wax paper such that the paper is snug to the surface but can still slide off without too much effort. The wax paper should be longer than the intended wind length but shorter than the mandrel. Tape the ends of the paper to the mandrel so that it cannot rotate independently during winding.
Apply several thin coats of mold release agent to the surface of the wax paper, allowing 5-10 minutes to fully dry.
Place mandrel back on the X-Winder, making sure that starting and ending wind measurements are within the wax paper region.
Mix one pump of resin and hardener and pour into the epoxy tray. Pull the tow through the tray until epoxy has reached the delivery head. Ensure that the epoxy regulator is properly tensioned.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the wind program. Watch to make sure things are running smoothly and that the first few passes are looking good.
Every 10-15 minutes, check the epoxy tray to make sure there is enough to cover the bottom part of the tray. Do not overfill the epoxy tray, as this will cause a buildup of heat as the polymerization reaction occurs, which can melt the tray or cause curing inconsistencies.
It is good practice to pause after each layer just to give everything a quick inspection before proceeding.
At the end of the wind, cut the tow and take a moment to appreciate the fact that the hard part is over!
Wrap the wind in one layer of bleeder/breather cloth. Try not to overlap too much as it might dry out the surface.
Tape and secure one end of a roll of shrink tape just off of the end of the wind. Run the shrink tape program or simply have the software spin the mandrel as you slowly wrap the shrink tape around the wind. Be careful: try to avoid wrinkling the tape and keep an even overlap as you move across the wind. Cut and secure the other end once the wind is completely wrapped.
Remove the mandrel and rod from the X-Winder and place in the curing oven. (The temperature should be above the activation temperature of the shrink tape.)
After the wind has been completely cured, cooled, and removed from the oven, the shrink tape and bleeder/breather cloth can be removed.
Remove the tape holding the wax paper to the mandrel, then remove the composite tube from the mandrel. Peel away the wax paper from the inside of the tube.
Congratulations! You have produced a composite filament wound tube. Inspect it for any defects or flaws and appreciate its cool pattern. It is now ready to be cut, sanded, turned into a rocket!
Disassemble the parts of the X-Winder which touched epoxy. Thoroughly clean these using a solvent such as acetone.
Check for and remove any fraying residue and clumps in and around the area.
Discard any epoxy mixing cups, used shrink tape, used bleeder/breather cloth, excess tow, and all other waste.
Make sure the X-Winder is unplugged when not in use.
Basic View (default mode)
• The Basic View shows a preview window of the job currently selected.
• The cursor becomes a magnifying glass (Zoom Tool) if you pass it over the preview window. Left-clicking the mouse zooms in and right-clicking zooms out. (Mouse scroll wheel can be used in any mode to zoom in and out.)
• Selecting the Settings button takes you back to the printer driver interface to allow you to change most of the settings for the job selected. Keep in mind that some settings cannot be changed after printing from your graphics program, such as print density and vector quality. If a setting is not adjustable after printing from your graphics program, it will be grayed out or not appear at all when you press the settings button in the UCP.
The Focus View feature allows you to quickly manually move the focus carriage to a desired position in the material processing field. This is useful for focusing, as well as testing whether the geometry falls within the material.
The Relocate feature gives you the ability to move the image in the selected job to another area of the engraving field. This feature does not permanently modify the original image location.
The Duplicate feature gives you the ability duplicate an image in a grid pattern. You can select how many rows and columns of the image as well as the spacing between the rows and columns.
The estimate feature approximately calculates the amount of time it will take the laser system to process the selected job. For more complex jobs, the estimate feature can take a while to estimate the job completion time. A job can be estimated while a machine is disconnected or turned off.
Basic View (default mode)
• The Basic View shows a preview window of the job currently selected.
• The cursor becomes a magnifying glass (Zoom Tool) if you pass it over the preview window. Left-clicking the mouse zooms in and right-clicking zooms out. (Mouse scroll wheel can be used in any mode to zoom in and out.)
• Selecting the Settings button takes you back to the printer driver interface to allow you to change most of the settings for the job selected. Keep in mind that some settings cannot be changed after printing from your graphics program, such as print density and vector quality. If a setting is not adjustable after printing from your graphics program, it will be grayed out or not appear at all when you press the settings button in the UCP.
The Focus View feature allows you to quickly manually move the focus carriage to a desired position in the material processing field. This is useful for focusing, as well as testing whether the geometry falls within the material.
The Relocate feature gives you the ability to move the image in the selected job to another area of the engraving field. This feature does not permanently modify the original image location.
The Duplicate feature gives you the ability duplicate an image in a grid pattern. You can select how many rows and columns of the image as well as the spacing between the rows and columns.
The estimate feature approximately calculates the amount of time it will take the laser system to process the selected job. For more complex jobs, the estimate feature can take a while to estimate the job completion time. A job can be estimated while a machine is disconnected or turned off.
When you have money but you'd rather have raw material, fasteners, and other fun things
Check out the Materials page if you're not sure what you want.
Jacobs sells at-cost and is often the best option available. Most commonly, plywood for laser cutting and 1/8" and 1/4" 6061 aluminum sheets are cheaper here than anywhere else.
Would you like some Delrin? Lexan? ePlastics is pretty cheap and easy to order from on-line. Would recommend.
If you need any 8020 extrusions or parts, this is the place to go. They give a 10% discount, but they sadly don't do sponsorships. They can also give
some design advice and they can answer more specific questions about 8020 that can't be answered on the website (you can also search the catalog)! Michael and Benson have been in contact with David Morton from there. His email is david.morton@tecotechnology.com
Good customer service, highly recommend.
Screws, bolts, washers, nuts, threaded rods, tooling, some stock, and similar are the most common purchases from McMaster. Many other parts (gears, linear bearings, pumps, etc.) are available but may be prohibitively expensive.
If you need pipe fittings, valves, regulators, or really anything for propulsion, Swagelok is our go-to supplier.
Buy components from Digikey. Really everything should come from here.
If you can't find it on Digikey, maybe you can find it here?
Apparently Arrow is actually the largest supplier of these three by volume, so you should probably be able to find it here if not at the other two.
80/20 Inc. has a fantastic website detailing a lot of information about their extrusions.
This page is intended to serve as a summary and introduction to these extrusions.
The most useful part of this page is probably the Tips and Tricks section at the bottom.
8020 is a brand of Aluminum extrusions. "Extrusions" just means that they are parts with a constant cross section that are extruded through a dye in their manufacturing process. 8020 sells an entire product ecosystem that revolves around their "T-slot" extrusions. Their cross section looks like this:
8020 parts are often used to build frames and other equipment quickly and more conveniently than alternatives (such as welding, manufacturing custom parts, etc.). They are widely used in industry for several reasons:
They are easy and convenient to use
While they can be pricey, they are high quality and are usually cheaper than a custom solution
They are very versatile and can be used for many types of applications
They can be expanded to include linear motion bearings, stanchions, guard railings, fences, etc.
The basic principle behind fastening 8020 extrusions is called the "2 degree drop lock"
The main idea here is that the edges of the extrusions are not perfectly parallel to each other, but rather offset by 2 degrees (this can be a pain in SW sometimes, be aware). When a fastener is tightened, it elastically deforms the extrusion, creating a strong normal force on the nut and fastener head. This normal force allows for a large static friction force to be applied, securing the nut in place.
For reference, on of these fasteners can usually hold up to several hundred pounds when installed properly.
8020 has a lot of options, which is fantastic. However, this can be intimidating for first-time users. This guide is intended to help you through selecting 8020 components for your assembly
For most applications at STAR, we do not use metric extrusions or fasteners. This leaves you with two choices for the extrusion series:
1010 - This is a 1" x 1" extrusion. This will usually be enough for most applications where the structure is not under significant or mission critical load.
1515 - This is a 1.5" x 1.5" extrusion. This is the maximum imperial sized extrusion, and is used for more "beefy" structures.
Extrusions are also available in non-square shapes. For example, a 1530 extrusion will measure 1.5" by 3", indicating that it is essentially two 1515 extrusions connected side by side. These are still compatible with other extrusions in their series
Note that for each of these extrusions, there are submodels such as "1515-S-Black-FB". These indicate unique features of the extrusion. Be mindful of these, since they can at times compromise strength or offer options for weight reduction. There are countless options, but these are a few to be aware of:
S indicates a smooth finish
Lite indicates a lighter but weaker profile. Lite gets abbreviated to L if there are other modifiers (about 22% lighter than regular
UL stands for ultra light (about 12% lighter than L, 32% lighter than regular)
Black indicates a black anodized finish. More expensive, questionably more corrosion resistant.
Fasteners are an integral part of 8020 product selection. The 8020 catalog provides a good amount of detail on the differences between fasteners, and their youtube channel is also recommended for seeing how these work in action.
There are several questions to keep in mind when selecting a fastener:
How strong will the fasteners be?
How much machining will be necessary on the profiles?
We can order parts pre-machined, but it does cost more money. Machining parts ourselves is also possible, but is very time-intensive.
How often will this fastener need to be removed? Will it need to be removed after the assembly is assembled?
What are the loads going to be on the fasteners?
A force applied perpendicular to the T-slot and the axis of the screw will differ greatly from a force applied along the T-slot, which will both be very different from a torque in the axis of the screw.
For small orders, 8020.net is fine. For larger orders, please email David at TECO technologies.
Don't make the same mistakes we did.
PLEASE PLEASE PLEASE if your budget permits order parts pre-cut and pre-machined. It saves a lot of headache on our side, and the whole point of 8020 is that it's easy.
If your budget does not permit, reconsider your budget. Machining and cutting 8020 for an average-sized project will take well over 10 hours in the machine shop for the average student.
If you've reconsidered your budget and still can't afford, buy extra length of 8020, since cutting and mistakes will eat up your length. Also order extra fasteners
Try to stick with flat plates and gussets. Anchor fasteners are difficult to access and expensive, and end fasteners require tapping into the aluminum, which isn't ideal for things that need to be disassembled frequently. 45 degree supports are also very nice for high-strength applications.
When tightening fasteners, you almost can't go too tight. Most people will not tighten the fasteners enough to engage the 2-degree drop lock on the first try.
Think about accessing fasteners when you create your assembly. A fastener is no good if you can't get in with a hex wrench to tighten it.
When creating 8020 assemblies in SolidWorks, use the models provided on 3D Content Central (https://www.3dcontentcentral.com/)
Be mindful about constraining these, since the 2-degree drop lock means that seemingly parallel planes are not actually parallel
8020 becomes very useful when you interface it with your custom parts. This is not very difficult to do, and essentially just involves including an equivalent flat plate fastener in your part.
How to put together some tubes
Rocketeers traditionally use friction fits for low-power, mid-power, and most L1 and some L2-level rockets. Take this example of a rocket with a single-deploy, motor ejection recovery system:
There are three interfaces marked with vertical lines; the green one is the only interface required to be separable, as it is where parachutes exit the vehicle. In this case, we rely on the friction between the electronics bay coupler (fore) and the booster tube (aft) to keep the upper and lower section from moving relative to each other on ascent after the motor has burned out.
If a friction-fit interface is not tight enough, drag separation can occur. While separation during powered ascent is less likely, after the motor has stopped producing thrust, it is possible that the drag force experienced by the lower section of the rocket (including fins) is greater than that experienced by the upper section. When this imbalance of forces occurs, it is possible for the lower section to accelerate relative to the upper section. This is known as drag separation, and is not always a bad thing; it can even be desirable if used for stage separation.
It can be more of an art than a science to get a good friction fit. Generally, we recommend following this (paraphrased) advice from Dave Raimondi (ex-LUNAR President, L3-certified):
Your friction fit should allow you to gently lift the rocket in the air by the upper section and hold it such that it is stable and not touching the ground. Then shake the rocket and make sure the bottom section separates with some effort, but does not require violent shaking.
To adjust your friction fit, either: remove/add masking tape to the coupler, or, if no masking tape remains and it is still too tight, sand down the coupler/inside of body tube. We recommend adding tape one layer at a time, either in entire rings or even half rings for fine-tuning. Use wide painters or masking tape for best results (> 1" wide). There is a fair amount of tolerance on the above advice; don't be too worried if your fit seems to be a little too loose or a little too tight.
Any rocket with dual-side dual-deploy recovery will require a stronger interface to keep the main parachute from coming out. Also consider using a stronger interface for larger and heavier rockets, as they may be subject to larger forces. Refer also to the many forum threads like these for more information:
Shear pins are fasteners designed to hold an interface together, but break (shear) when recovery energetics (black powder, usually) are activated. They may also be used to retain deployable payloads. The driving mechanism for shear pin failure is the transverse loads applied by each section of tubing (coupler, body tube) as pressure is built up inside the airframe; the shear pins are not vaporized, melted, or otherwise affected by recovery charges.
STAR members have traditionally used #2-56 or #4-40 nylon screws (e.g., from McMaster-Carr) as "shear pins". While these screws technically have threads, they are often more of a press-fit than screwed into the airframe. No female threads (nut/threaded insert) are required. Shear pins have been effectively used with BlueTube and fiberglass airframes.
Using too many or too few shear pins can result in extreme quantities of black powder being required, or the premature separation of the airframe in flight, respectively. STAR has experience with both of these scenarios. Only testing can truly help you avoid these outcomes. Short of testing, precise calculation of the loads may be helpful; however, it is generally quite difficult to estimate exactly what loads will be applied to each shear pin.
Note that dynamic loading when the main parachute opens is usually far higher than any other load during flight; if shear pins are used to retain a payload through/after main parachute deployment, pay special attention to this interface to ensure it does not break prematurely.
When it comes to larger or more complex rockets, it is expected that you will have one or more interfaces that you need to be separable during assembly, but do not come apart during flight. These are generally held together with some sort of fastener. One common example of this type of interface is a nosecone that detaches from the payload tube to allow for the insertion of a payload, but does not need to detach during flight.
To use a weld nut or nut plate with epoxy for a coupler-body tube interface, follow these rough steps (also see below for references with pictures):
Test fit coupler and body tube together and tape/ hold interface so tubes do not rotate relative to each other
Drill a hole (free fit tolerance for the screw that will be used) radially through both body tube and coupler
Insert a screw radially inward through the hole, going through both the body tube and coupler.
Hold the nut on the inside of the coupler and thread it onto the screw
Mark out area for epoxy around footprint of nut
Remove nut and apply epoxy, taking care to avoid the hole where the screw will go. Remember that when the epoxy is compressed, it will spread out, but should not enter the screw/nut interface.
Thread nut back on to screw, stopping right before it touches the epoxy
Pull screw radially outward, pressing nut into epoxy
Hold nut static (use pliers if needed, clean afterward with isopropyl alcohol) while screwing in screw completely to apply medium pressure
As epoxy cures, make sure that the screw is still removable. It is very possible to accidentally permanently epoxy the screw to the nut, rendering the connection useless. We recommend keeping pressure at least until the epoxy has set, periodically removing the screw to check that the threads are still useable
Historically, STAR has used #4-40 pan head sheet metal screws (from ACE Hardware or McMaster-Carr) to semi-permanently attach Blue Tube interfaces. Sheet metal screws are similar to wood screws in that they have deep, aggressive threads and a sharp point; however, unlike wood screws, they are threaded all the way until the head. This property makes them useful even at very short lengths (1/2" or 1/4" long).
As a sheet metal screw directly cuts into the airframe, the material that said sheet metal screw is holding onto is gradually removed each time the screw is inserted and removed. Practically, this manifests itself as the screw feeling loose and/or simply falling out after too many uses. The screw may also bind in the interface at an angle, instead of remaining perpendicular to the long axis of the rocket.
While Blue Tube generally accepts ~10 or more assembly/removal cycles without any issues and up to 20-25 without serious concern, you may start to notice sheet metal screws in fiberglass becoming loose after as few as 4 cycles (typ. 6-8). This is in part due to the fact that Blue Tube, as a paper composite, will recover its shape more easily after being deformed. While it is possible to attempt to remedy a too-large hole with some epoxy, it is often easier to simply drill another hole and fill the previous one entirely. Depending on the epoxy used, this may take up to 24 hours to completely cure. For a project team on tight assembly timelines and an interest in professionalism and reliability, we do not recommend sheet metal screws for composite airframes. Do not underestimate the potential timeline and build quality impact a poor tube connection can cause.
Self clinching nuts, sometimes called PEM nuts or press fit nuts, are nuts designed for installing a permeant fixture of female threads in a hole of sheet metal.
After a hole is drilled with the right diameter, the nut can be press fit into the hole. This process will deform the metal to envelope the back tapered shank and hold the nut in place, as well as imbed serration to provide torque resistance.
Rockets are usually not made of sheet metal, but these nut have been seen to work on fiberglass tubes. Do note that for tubes under 2.5" in diameter, the curvature of the tube may be too great for the nut to properly work, as they are design for flat surfaces. It is also important to buy nuts that are suited for the thickness of the tube wall. Additionally, ensure you have the right size drill bit, as hole diameter is crucial to ensure the nut press fits well.
Specialized tools can be used to press fit the nuts into place, but simpler methods can also be effective. By using a screw or bolt that is compatible with the nut, one can tighten the screw and effectively "press" the nut into the drilled hole. A washer can be used to create a better clamping surface, but may not be necessary.
Some people choose to also add epoxy to the nut to increase the strength of the nut to the tube. It likely depends on serval factors for how well the nut actually stay in place, but in flight when the nuts are engaged with the screws, they shouldn't go anywhere. The screw shearing off is more likely than the nut failing all together. Multiple nuts should be used to make a good permanent connection between to pieces of the rocket. It is also recommended that the screw sizes should be slightly longer than they need to be, so in the case of the screws shearing off, they can still be removed from the nuts. Even then, it is recommended to not use these nut for shear pins/screws, and to go with the more traditional technique outlined above.
It is certainly possible to epoxy an ordinary hex nut (see: ) to the inside of a coupler and thread into it with a machine screw. That being said, we recommend using one of the below options for better reliability and/or convenience. Trying to properly position a normal or low-profile hex nut can be difficult and can result in getting epoxy in the threads or a poor bond with the airframe.
Nut plates and weld nuts essentially refer to the same thing: a normal nut, but attached to a wide base that permanently attaches to a surface. Once the weld nut is attached to a surface, it offers female threads for a removable but secure attachment (similar to a ). Traditionally in aerospace (especially planes!), nut plates are attached to a surface with rivets while weld nuts (more common in cars) are literally welded to a surface. "Adhesive-mount nuts" are also sold with the explicit purpose of being attached with an adhesive, although most weld nuts/ nut plates are fine to use with epoxy.
See this fantastic tutorial on how to use weld nuts/nut plates with fiberglass airframes: A similar write-up can be found in Apogee Newsletter 341:
Pros of sheet metal screws | Cons of sheet metal screws |
Simple | Limited number of uses |
Slightly cheaper than alternatives | Less reliable / reproducible |
Little upfront work | Require significant rework after max uses |
Fairly accepting of too-small holes in soft materials | Difficult to size holes for in rigid materials |
Tutorials specific to the Avionics subteam
Applicable to club or personal rockets
Rustoleum 2-in-1 Paint+Primer has worked fine in the past; generally people use spray paint to paint rockets.
Always wear a P100 respirator when using spray paint! Spray paint can cause serious lung damage, brain damage, cancer, and more.
Environmental conditions matter when it comes to paint. Ideally, paint on a dry day with no wind and a relatively comfortable temperature. If there is wind, paint such that the part is downwind of the can/you. Colder temperatures may mean you will have to wait much longer for paint to dry. Excessive humidity can also affect your finish; try to avoid painting when it is raining or about to rain.
Prepare surfaces for painting. For fiberglass parts, this means clean with isopropyl alcohol / water mixture, sand lightly with 100+ grit sandpaper, and then clean off dust with tack cloth or more IPA mixture.
Apply a light coat of "primer" (may also be paint+primer). No need to use the same color that your final coat will be, but choose a light primer color if you want a light-colored part.
Apply one to two more light coats of primer, waiting about a minute in between each coat. Do not worry about completely covering all spots, but do your best to apply a thin, even coat. Follow the instructions on the can with respect to distance from the part.
Wait the required amount of time (usually 24 hours) for the base coat to dry
Apply 2-3 coats of the final color you want, about one minute apart. Do your best to avoid spending too long on one spot; it's easy to apply another coat, but it's hard to undo a puddle or run!
Wait 24-48 hours for the outer coat to dry
Apply 2-3 light coats of clear coat, moving slightly more slowly on the last coat to achieve a glossy finish. The clear coat will protect the paint underneath.
How to design fins that do their job while imparting minimum drag, weight, and risk
Root chord - edge of fin attached to body tube
Tip chord - edge of fin parallel and furthest from body tube
Leading edge - the edge facing the front
Trailing edge - the edge facing the rear
Semi-span - distance from the root to tip chord
Aspect ratio - ratio of a fin’s span squared to its area
Taper ratio - ratio of tip to root chord lengths
Root chord: ~2 diameter lengths
Tip chord: ~ 1 diameter length
Semi span: vary this dimension for appropriate stability
Fin tabs: make contact with the motor tube and typically between two centering rings.
Placement: close to the back of the rocket between two centering rings.
Material: The main options for the fin material are plywood, fiberglass, and carbon fiber. The material depends on the rocket being made and the durability needed.
Fillets: Create fillets between the fins and the airframe using epoxy. This will increase aerodynamics while ensuring the fins are reinforced.
Sanding edges: Sand the leading edge and tip chord of the fins to decrease air resistance and increase aerodynamics. This is optional, but highly recommended.
Check the Airframe OpenRocket tutorial to learn about adding and designing fins in OpenRocket.
As the rocket flies at high speeds, the fins will vibrate. For lower speeds, this is not a problem because the amplitude of vibrations will decrease from the air. This is problematic when the rocket speed exceeds the maximum fin flutter speed at which point the air will amplify oscillations to the point of destroying the fin. The maximum fin flutter can be calculated from the following formula:
Flutter speed (Vf) - max speed before the fins break
Shear Modulus (G) - amount of deformation associated with a certain amount of force
Speed of Sound (a)
Wing Thickness (t)
Root Chord (cr)
Tip Chord (ct)
Semi Span (b)
Air Pressure (P)
Aspect Ratio (AR) =
Taper Ratio (λ) =
Wing Area (S) =
It is important to dimension your fins so their maximum fin flutter lies above the maximum rocket speed.
Thicker fins are more structurally stable, but they also increase the weight of the rocket and the drag experienced during flight. The force of drag can be calculated with:
Drag Force (Fd)
Air Pressure (p)
Velocity (v)
Drag Coefficient (cd) - how well air moves around the fins
Area (A) - increases with more thickness
The drag coefficient can be lowered by improving the cross sectional area of the fin. Cross sectional areas include square, rounded, and airfoil in the order of lowest to highest performance. The fin thickness should also account for fin flutter as a low thickness can risk damaging fins during flight.
The primary purpose of fins is to correct the rocket during flight such that it continues on a stable trajectory. In order to do this, the center of pressure should lie below the center of gravity. This is so the rocket is stabilized or pointed upward if there is a deviation from the stable configuration. The center of pressure is the sum of the pressure field on the rocket, which creates a lift force.
Stability (S) - measured in cals
Center of Pressure (CP) from the front of the rocket
Center of Gravity (CG) also from the front of the rocket
Rocket diameter (d)
As a general rule of thumb, the stability should fall between 1-2 cals. Below this range, the rocket may not correct itself enough. Above this range, the rocket may overcorrect. By increasing the surface area of the fins, the center of pressure will move towards the aft end and increase the stability.
Fins can be attached with a fin jig. This method involves epoxying the fins onto the motor mount, at equal spacing, through slits made on the main booster tube. We ensure that the fins stay perpendicular to the airframe by using a fin jig: a lasercut "spacer" that holds the fins in place while the epoxy dries.
Fin jigs are used for fin sizes where epoxy adhesion is sufficient. For larger or heavier fins (here we used fiberglass), it might be best to use fin brackets.
To be added later: schematic of fin jig (emphasis on the hole for the rail button), epoxy used, carbon fiber fillets, circle clamp, sanding fillets.
As stated above, fin brackets are convenient for larger and heavier fins where epoxy is not strong enough. A fin bracket is typically an L-bracket that gets bolted into the side of the fin and the airframe. We have not had to use fin brackets yet.
A fin can is a single-piece setup that includes all the fins attached to a cylinder that slides onto the booster tube. We have also never used this method.
See this detailed link for information: http://jcrocket.com/tttjig.shtml
To quote:
High performance rockets put a huge amount of stress on the fins. Large heavy rockets put large amounts of torque on the fins and high speed rockets can cause the dreaded fin flutter. All large rockets subject fins to high forces on landing.
Reinforcing wooden fins with fiberglass or other composite reinforcement helps to make them stronger. (G-10 fins generally don't need reinforcement for strength.) However, for very high speed rockets, you also need to stiffen fins and carbon fiber makes an excellent reinforcement for this purpose.
Fins can be covered with appropriate reinforcement before being mounted to the body. This will make the fins stronger and stiffer. For conventional rockets with motor mount tubes smaller than the body tube, the fins are bonded at three points: outside the MMT, inside the BT and outside the BT. However, for minimum diameter rockets, the fins are bonded only at one point: outside the BT.
For minimum diameter rockets, it is desirable to reinforce the fin/BT joint for strength. In addition, because minimum diameter rockets are often high performance, it is desirable to stiffen the fins as well. The best way to do this is to laminate the fins tip-to-tip with carbon fiber and fiberglass. By laminating the fins tip-to-tip (and over the body tube in between), we reinforce the joint, stiffen the fin and make a solid fin can.
Learn git and avionics' git workflow
You'll find all of Avionics' sources on our Github, including schematics, layouts, firmware, and software. This Github org also contains repositories of other STAR subteams.
Windows 10 supports running a proper Linux development environment using Windows Subsystem for Linux. Installing and using this is highly recommended on Windows.
Make sure you have a Github account and you have joined the Github STAR org Avionics team by messaging the avionics lead (currently Cedric Murphy @Andalite1999#4769). For git installation, see here.
There are many great git guides out there!
Learning git takes time and can be intimidating! If you are worried you're about to mess-up your repo, or have already messed up your repo, ping someone in Discord!
Short list:
Clone the repo.
Create a new change branch from the master branch.
Make changes.
Rebase onto master branch.
Submit a pull-request on Github.
When approved, merge into master!
Clone the "repo" onto your local computer in by running the following command in terminal:
This will copy the repo and all its current files into your directory. Make sure to read through the relevant documentation in the repo before making any changes.
The --recurse
(short for --recurse-submodules
) tag tell the computer to execute
after cloning. For libraries that are used in multiple repositories, such as hardware-sch-blocks,
it is cleaner to create a separate repository for the library and embed it as a submodule instead. Because submodules are not normally downloaded with git clone, --recurse
is necessitated. For a thorough guide, see tutorial.
A branch is a separate copy of a git repo that can have its own changes separate from other branches. A branch can later be incorporated back into the "master" (main) branch. We use branches to develop and test changes before we merge them into master, which we expect to remain stable and flight-ready.
Create and checkout a new branch:
Switch to an existing branch:
Edit or create files with your desired text editor, which should be vim.
Register changes with git using git add
. For example if a.txt
is a new file and b.txt
is a modified file, do:
Then, "commit" changes into git. This saves changes into a snapshot which you can look back at.
Often you will work with other members on a change on a given branch, so the new changes (the commits) on the branch will need to be pushed to Github. Do this by running:
The first time you do this from a new branch, git will tell you that no remote exists. Follow the instructions it outputs to create the branch on the Github side.
Often, there will be many commits on a branch. To keep git history on the main branch concise and informative, we often squash the commits on a branch into a single commit that describes the whole change. There are two primary ways of doing this:
or
While squashing changes gives a single commit that describes the entire change of a branch, rebasing onto master ensures linear commit history of the master branch in case there have been changes on master since your change branch was created. Rebasing does this by essentially taking the current master branch and replaying all your changes on the change branch onto the new master. Rebase onto master, once commits are squashed, by doing the the following from the changes branch.
You may encounter rebase errors here depending on what changes ocurred on master. Git will let you know which files you will have to merge manually and how to continue when done fixing.
Make sure to test all functionality again after rebasing onto master!
Finally, the change is implemented and tested. A pull-request is where the final review of the change is done before it is merged into master.
To submit a pull-request, do a final git push
and then go to the Github website. Select the branch and using the Github UI select submit pull-request. Add relevent reviewers and ping them on Discord.
As reviewers comment, you will likely need to make changes. Once all changes are made and reviewers approve the change, hit merge!
Some commands you will find useful.
Show commit history:
Optional: Download http://leo.adberg.com/gitconfig and save as ~/.gitconfig (replacing user info) To see a view of all commits and branches:
To see the status of your local repo, you can run:
These slides have nice descriptive diagrams! Check it out!
Avionics uses Trello for project management
Probably best said by Trello itself.
Trello is a project management software which allows us to track tasks which need to be done, what stage projects are in, and what everyone is working on. It helps streamline our workflow by making sure we always know what we have done, what we are doing, and what we have left to do.
Create a Trello account and message the Avionics lead to gain access to the above Trello team for Avionics.
How to design a schematic and layout for PCBs
Some parts of this page may be out of date (in particular, the section "Before You Submit"). The rest of this page is a great reference!
A printed circuit board, or PCB, is the backbone of hardware design. These cheap, compact, reliable boards allow us to implement circuits into a greater system. They are better than alternatives in that they provide form (hold everything together) and function (make good electrical connections). They are built from conductive copper layers separated with non-conductive substrates and include things called vias, tracks, and pads which will be discussed later. While the process of making PCBs may seem long and frustrating, this tutorial will guide you through the most basic parts of making a good PCB.
In order to start making your PCB, you will need a design. It should meet your system specifications under all relevant conditions (such as temperature or vibration) in little time for little cost with few iterations (don't worry if you have to redo your design, but don't just guess and check). Your design should be testable and fail minimally. You can start a design by identifying what particular electrical components provide which functions. These components are then put into something called a schematic, which essentially pieces these components together to make your design work.
Once you have your functionality decided upon, it's time to start developing the design a little further. At this stage, continue updating your specification document or create a new system architecture document that will contain all design choices to achieve the desired functionality.
This is where questions like "do we need a microcontroller or can this be done without one?" or "how are we going to power this board?" should be answered. As you do this, feel free to update your specification document as you realize what additional functionality is needed. At this stage, you should also consider exactly how your board may interface with other devices and people (radio, serial communication, LEDs to communicate power/status, switches, etc.)
Depending on your familiarity with the available hardware, you may not be able to fully specify the architecture before taking a look at the next section, Selecting Parts. It is perfectly fine to go back and forth between looking at available components and updating the system architecture.
Selecting parts to use for your design may seem like a tedious task, but it's extremely important to get right for your project to work. After determining your desired functionality and architecture, you know what passive component values and ICs (integrated circuits) you will need, but that is only a small part of selecting the physical part that will end up on your physical board. Here are some things to consider:
Components come in may different sizes and shapes: some are larger, some are smaller, some are impossible to solder, etc. It is extremely important to pick a correct form factor for each component, or your design will be impossible to assemble.
Solderability
How small is the component? For passives, CalSTAR uses 0603 Imperial or larger.
Does it have leads or is it marked QFN (no leads) or BGA (ball grid array - under the IC)? If the latter, you will need a reflow oven and cannot solder by hand. If absolutely necessary, QFN/LGA components may be solderable at a hot-air station; ask a subteam or project lead if you think this might be necessary.
Surface Mount vs. Through-Hole
Surface Mount (SMT/SMD) and Through-Hole (THT or DIP) are two forms the component can take. The former lies flush on the board and are usually smaller while the latter is put in a hole through the board.
Passives and ICs should be SMD, while connectors are usually through-hole. The more compact the board, the better.
When looking at an IC's application circuit schematic/layout, consider the complexity and the sensibility of the externals required. If it is not appropriate for your design, consider another IC. Many ICs require an extensive network of resistors, capacitors, etc. to function properly.
In general, while searching for parts, whether from Digikey (preferred) or Mouser or Adafruit, read the datasheet and specs carefully to ensure they fulfill the requirements you need. You need to check that is can drive the correct load, provide or handle enough current, is powered by the correct voltage, is the right size, and for passives, is the right value. Here is an example of a search for a specific 10kOhm 0603 SMD resistor from Digikey:
Microcontrollers are essentially the "brain" of the PCB. You can program them to perform specific tasks (for example, light up an LED or interpret sensor data). They are usually quite complex and have dedicated pins for their different functions. GPIO pins (General Purpose Input-Output) are especially useful for customization. CalSTAR has previously used AVR processors by Atmel (ATmegas, the same as commonly found on Arduinos), but we are now using 32-bit ARM chips made by STMicroelectronics (STM32F401RET6, for example).
Transistors are three-terminal semiconductor devices used to amplify or switch electronic signals and electrical power. There are many different types of transistors, but the most common that you'll see are BJTs (bipolar junction transistors) and (MOS)FETs, which are (metal-oxide semiconductor) field effect transistors. Transistor physics is generally not covered well in lower-division EE classes; feel free to ask someone for help picking a transistor if you're unsure.
DC-DC converters converts one DC voltage into another. For example, a 12-V battery voltage may need to be stepped down to 5 or 3.3V. There are two common types: LDO and switching regulator. The LDO (linear drop-off) is generally simpler to implement into a PCB because it has fewer external components, but it uses a lot of power.
Passive elements include resistors, capacitors, inductors, oscillators, buzzers: anything that either consumes but does not produce energy or that is incapable of power gain (unlike a transistor that is capable of amplifying). Capacitors and inductors can used for oscillation (like a voltage regulator). Capacitors can also be used for coupling/decoupling.
These are usually LEDs or buzzers: anything that indicates a specific function is occurring. LED's are important to indicate whether power is being supplied to a PCB, for cases of safety and debugging. Buzzers can be used when the PCB is obscured (like in the rocket) and the board LED is no longer visible. Small green SMD LEDs are common to indicate power, while other colors can be used to indicate activity or danger.
A diode is an semiconductor device with two terminals that allows for the flow of current in one direction only. An LED (light emitting diode) is one example. Diodes can be used for reverse polarity protection, i.e. if you connect power in the wrong direction, current will not flow and therefore will protect your circuit. Zener diodes can also protect surges by having one terminal connected to a power net and one connected to ground.
A fuse is a safety device that prevents a short circuit from damaging the rest of the board. There are two types: resettable and non-resettable fuses. A non-resettable fuse works by allowing the overcurrent to melt a small piece of metal in between its terminals so that it becomes open. A resettable fuse has a material in between its terminals that, instead of melting, increases resistance and cuts off current flow.
These are the components that are usually soldered to the edge of the board that allow it to connect to the necessary peripherals. For example, a battery will need a connector (usually an Anderson PowerPole), while screw terminals may be used for wire connection to other PCBs.
There are many different ICs (integrated circuits) that your PCB may need in order to function. This includes sensors (like a GPS, altimeter, accelerometer, or gyroscope) to provide information about what your project is doing (in our case, what is happening during flight). In addition, a radio IC, with attached antenna, is useful for communicating commands to the microcontroller during testing and flight.
While selecting your parts, you will need to write them down. Each component requires a lot of information in order to purchase the correct one. Here is an example BOM, with the necessary columns:
The manufacturer part number is the number of the manufacturer (for example, Infineon) of the component while the supplier part number is the code of the supplier (for example, Digikey). "Ref Des" stands for Reference Designator, which is the number of the component in your schematic. Make sure that you select the correct size for all components and that their packages are appropriate for your layout. For example, make sure resistors/capacitors are 0603 and that you distinguish between through-hole and surface mount.
What is a schematic? They are drawings that represent elements in a system using abstract symbols to give information without unnecessary details. You can implement these schematics in your PCB design software, as discussed in the information notes at the top of this page. In general, signals should go from left to right, top to bottom, with higher voltages at the top and lower at the bottom. Here is an example in KiCad (the long parallel gray lines are to indicate the separation of functions in the circuit):
Notice the connector to power is at the top left and the output is at the bottom right. The amplifiers follow the "high voltage up-low voltage down" rule and everything is separated by function.
You will want to use an appropriate grid size to align your wires (about 50 mils - 1 mil is 1 thousandth of an inch, NOT one millimeter) and use labels to make the values and functions of each part clear.
Most ICs are drawn as rectangles. A resistor can be shown as a long rectangle or a zig-zag shape. Capacitors are using two parallel lines of some length, while a battery is a long line in parallel with a short one. Some shapes are made for special functions (a triangle is usually an amplifier). Here are some examples:
Sometimes you will need to make a new schematic symbol if your software doesn't provide it. Be sure to group pins on your new symbol by function, not the location on the physical package. Power should be on top, ground on bottom, and inputs on left and outputs on right.
Once you have your symbols in your schematic, you might notice they will have associated letters and numbers. For example, U1 or R4. These are called reference designators, as shown above in the example BOM. The letter tells you what kind of component it is. "U" means some IC while "J" is a connector and "R" is a resistor. The number is just clarifies which of that type it is. Naming 15 different resistors "R" isn't helpful, so they are labeled R1 to R15. These are usually automatic, but you will have to hand-label their values, of course.
When your schematic is complete, you will want to run ERC, or electrical rules checker, through your software. In Diptrace, this is done by clicking "Verification" at the top menu bar and then selecting "Electrical Rules Check" from the drop-down menu. In KiCad, it is Inspect>Electrical Rules Check. This will ensure that your wires are connected appropriately and that you didn't make any egregious errors.
What is a layout? It is like a map for how your physical board will be arranged. PCB's are built layer by layer with copper layers for connectivity and insulating layers to provide mechanical rigidity and form. The boards are covered with something called soldermask, so that when you start soldering, the solder will stay only within the exposed pads you designate. These pads are made of copper and connect to the copper layers in the board. Here is an example of both through-hole and surface mount pads with the lines of connectivity in light green (the other smaller holes you see are called vias, which you'll learn about later):
Layout begins by assigning footprints to each of the components in your schematic. Footprints are the physical representation of the schematic symbol of a component. For example, a capacitor footprint will usually be two parallel rectangles, as shown below:
There is a function in your software that allows you to import your schematic so that the footprints connect like they're supposed to. This is called LVS (layout vs schematic) and is often included in DRC (design rule check).These connections are those light green lines you see above. You can even use the autorouter to do this, but it's not a very intelligent function. It's better to do it by hand. Make sure that when you are connecting pads to one another that none of your lines cross! Your layout needs to be planar. You may find that this proves difficult, if not impossible, so to get around this, use vias. Vias, which are holes that go between the back and front of the board, need to be proportional to the width of the trace (the term for the light green lines). See the following figure. Below is a calculator for finding the appropriate width of a trace, which need to be larger to carry large currents.
When routing, use net classes (e.g. power, ground, etc), and try to keep traces short, especially for high currents, since traces have resistance. Fill zones, or copper pours (see example below), help to dissipate heat across the board and connect large areas together. Follow datasheet recommendations for help.
Once you've arranged them in a way that makes sense for your project (i.e. connectors should almost always be at the edge, with the SMT IC's near the center), consider the Design Rules. These are the minimal manufacturability requirements of the board. For example, drill sizes have to be a certain diameter, along with trace widths. The smaller everything is, the more difficult and expensive it will be manufacture, if not impossible. At the end of your design, you will run DRC, which is similar to ERC, but instead checks that you have followed all the rules of manufacturability. Here is an example of a layout:
General steps to follow:
Begin by drawing edge cuts. This is the yellow rectangle that surrounds the components. It determines the outermost edge of your board. Usually, the size of your board is dictated by mechanical requirements, so this is almost always the first thing you should do.
The other two colors of rectangle define the ground and power planes that you will be connecting your components to.
Check ICs' datasheets for a recommended layout. How much space does the recommended layout require? In the above example, U1 had a recommended layout that suggested the capacitors and diodes around it be arranged as so, with copper pours connecting them where appropriate.
Next, place the connectors at the edge of your board. In this example, it would be the USB connector (it wouldn't make much sense to put that in the middle). Place power-related components and their external components after that, according to the datasheet's recommendations. Include any fills or thermal vias that it recommends.
Place the rest of your components (usually passives and indicators) and then add any additional filled zones you may need.
Lastly, route all nets not connected to a fill zone and adjust the size of your fills as necessary after creating them. Add routes and vias to connect your fills.
Other things to consider include the following:
Traces have resistance (they will heat up, decreasing efficiency and wasting power), have inductance (current through them can't change instantaneously), and have capacitance (causes signals on one wire to show up on others). Increasing trace width reduces resistance and inductance. Decreasing trace length does the same.
Vias have inductance and add length, so put them in parallel when you must use them.
Decouple correctly by placing capacitors close to the component you are decoupling and size the capacitor correctly so that inductance doesn't dominate. See datasheets for recommendations.
If you are creating a complex with a lot of components, consider using the "Manhattan Routing" strategy. It has only one simple rule: all horizontal traces go on one layer and all vertical traces go on another layer, and traces go to the other layer (with a via) whenever they need to turn. If your board is very simple then this probably isn't worth the effort, but for large or dense boards this strategy can make your life much easier.
Make sure you have done all of the following before a review, and before boards are submitted for manufacturing.
All passives should have values visible.
Important nets should be labeled
E.g.: V_in, 3.3V, GND, DEBUG_RX, DEBUG_TX, ACCEL_SDA.
Text should not overlap.
Components that are not easily replaceable should have Manufacturer and Datasheet filled out in Component Properties.
"Not easily replaceable": ICs, connectors, fuses, any unusual components such as a massive electrolytic capacitor.
Schematic should be broken up into modules (surrounded with a box) to aid readability. Label each module with text.
E.g.: radio, voltage regulator, reset line, programmer port.
Use netports to prevent lines going everywhere.
Test points should be added to ALL nets that we MAY want to measure at some point.
Double check all patterns
Add silkscreen
Pins on ports such as UART, programming ports, actuators, etc should be labeled
Move reference designators (RefDes) if necessary
Tip: F10 allows moving reference designators, 'r' for rotate
Place board name and version (eg Ground Station v3)
Calstar Logo (use reflected version if placing logo on the back of a board)
File > Renew Layout from Schematic
Verification > Check Net Connectivity
Verification > Compare to Schematic
Verification > Check Design Rules (F9)
Use to calculate impedance of traces, primarily for matching against 50 Ohms
Note: we have our boards manufactured to be 31 mils (this is the substrate height)
The substrate in our case is FR4
Use to determine minimum required trace widths based on current range
Bay Area Circuits:
Stay within BAC's standard capabilities
InstantDFM is a simple tool from bay area circuits that you can use at the very end of the board design process to verify that your board meets their manufacturing requirements (like minimum trace widths, via sizes, copper to edge clearance, etc). Before you submit any board for manufacturing, you should always run it through instantDFM to verify that there are no errors.
Getting started with the development environment for the Avionics codebase
Avionics distributes a container which contains all the tools for compiling our firmware. Some of the development tools we use for firmware development are a mild pain to install (particularly for beginners), so using the container is recommended for quick set up.
If you have tried out the container and have problems given your setup, and you really want to install yourself, go ahead. This is not recommended unless you are well acquainted with installation of compilers, etc.
If on Linux, there's too much variety to put anything here. I'm sure someone in avionics will want to help! Podman is very easy to use on Fedora and works out of the box.
If on Mac, this is all currently untested.
On Windows, you the recommended procedure is to install Windows Subsystem for Linux (WSL) and run Podman within it.
Since WSL is a non-standard linux environment that lacks of some important syscalls and processes, Docker cannot be run on WSL without some hassles. Podman has been tested on WSL, and you should follows the instruction below.
Once you finish, install Podman by running
Then, run the following instruction to create and modify the config file to make it run on WSL:
Then, use an editor of your choice, open /etc/containers/containers.conf
with sudo
:
Uncomment the line with events_logger
, then change the value to file
.
Uncomment the line with cgroup-manager
, then change the value to cgroupfs
.
You should be able to run the docker file right now. Note that you must run Podman with sudo
, or you won't be able to do anything. If you are getting No CNI Configuration file
error, do the following steps:
Run sudo podman network create
. It should give you a filename.
In the command you used to run docker, add --net <config-name>
after podman run
. <config-name>
is the filename you got from the first step.
First download the toolchain container image.
Then, create a directory where the files in the container will be stored.
The location of this directory can be viewed with :
Finally, create the container
Once the container is setup, it can be started with:
You can enter the toolbox to a bash
prompt with the below. This is where you will be actually running commands to use the compiler, etc.
Finally, once the container bash prompt is exited with exit
, the container can be stopped with
An alternate way to transfer files is using the Visual Studio Code editor. This may be convenient if you already use VS Code, and may be a method that works if this does not. See the VS Code & Containers
section.
To copy a file from the image to the host system (your normal operating system), you need to first get the mount point of your workspace by running
where star-workspace
is the volume name. If you use another volume name, you need to change the command accordingly. You can save it to a environment variable to avoid copying the long path every time.
Since the path is usually only accessible with root privilege, you need to copy it to a place that you can access without sudo
, like your home directory:
Then, if on Windows, open Windows Explorer, type in \\wsl$
in address bar. For every distros you install, you can see a folder with the same name as the distros in this folder. Go to the distro folder that you use to run Podman, and go to the path you copy the file to in the last step, like home/<user-name>
. You should be able to see the file you want in that directory, and you can copy and paste it to anywhere you want in your Windows file system.
If not on Windows, simply open a terminal and go to ~
. The file will be there.
Then, go to the "Remote Explorer" tab on the left bar of VS Code, right click on the container you created in the previous step and click attach to start a VS Code instance in the container. From here you should be able to open a terminal inside the container by going to Terminal->New Terminal
and interact with the filesystem through VS Code and clone stuff, open folders, etc.
In this section we detail how to compile code into binaries which can be written onto the hardware.
'Firmware' is the code which runs on the hardware, named so because it is 'closer to the hardware' than normal desktop software.
First clone the desired repository from within the container, e.g.
Then from within the repository, clone the submodules and run mbed deploy
Finally, compile with a command like
Check the repository Readme for details on the command to run to compile. The output, the binaries to flash to the microcontroller, will be put in the output
folder.
To create a new project called mbed_project
, run the following:
To compile a project, run the following from within the project folder
The target, NUCLEO_F401RE
is a development board that has the STM32F401RET6
microcontroller on board, the same microcontroller unit (MCU) that we use. The toolchain selects which compiler we are using.
This should give you something like the following if it compiled successfully.
Find libraries by searching in the search bar on mbed's website. Then, once on a library's page, look at the box titled "Repository toolbox" and select the down arrow on the yellow "Import into Compiler" button.
Then select "Import with mbed CLI" and copy the command listed.
The command should be of the form mbed add <project link>
. Run this command from command line inside your mbed project.
'Flashing' a program onto a microcontroller means to write the compiled code onto the microcontroller to be run when the microcontroller is powered off and back on.
As of right now, usb-detection and programming through the container is not working. Instead install and use a utility on the host system.
Windows: Download and install the St-Link Utility from the file below. To use, first File > Open file
the binary of the program output by mbed compile
. Then Target > Connect
to the board, and Target > Program & Verify
To use, open stlink-gui and perform similar steps to the windows version to flash.
Alternatively, use st-info --probe
to search for programmers and st-flash write $binary_output_file 0x8000000
to flash.
Please note that there is a board design DeCal that can give you a more detailed understanding of how to build PCBs: . Though this tutorial will follow the format of the decal's , this page is just an introduction. You can access the syllabus and material at this link: . Here is another useful resource on PCB design: h
Board design "useful tips" document from the aforementioned board design decal:
Before starting anything else, make a . This should outline exactly what you want your board to do, but should not specify implementation details. For example, a telemetry and power control board might be expected to transmit and receive data at 96 kBits/s, provide up to 500 mA at 5V for 6 hours, etc. Each of these desired functions should be testable before final deployment of the system (i.e. a function like "doesn't run out of power on the pad if there's a delay" would be better written as "provides up to 500 mA at 5V for 6 hours").
Your specification document should be roughly 0.5-2 pages long, depending on the complexity of the project. You may refer to a higher-level system architecture document, or even omit the specification document and simply use a section of a system architecture document as your spec, depending on how far design work has progressed. Make sure to also refer to the rules and regulations of whatever competition the board is for (); explicitly citing these in a spec document is always good.
Different from the component package, this is how the components are actually shipped. Make sure you can order the amount you want; some components are sold in units of 5,000! Generally, Tube, Tray, and Cut Tape and fine, whereas Tape and Reel and Digi-Reel have minimums in the thousands. See the for more details.
does an excellent job at summarizing when you should use a BJT versus when you should use a MOSFET.
A switching regulator, on the other hand, is relatively efficient with power and is generally more precise. These converters are important to supply the correct voltage to a component in order for it to work properly. A switching regulator that steps up voltage (at the expense of current) is known as a boost converter, while one that steps down is known as a buck converter. There are also .
When you have finished your layout, go through this to ensure that your board is ready for fabrication.
Use the HOPE PCB Decal checklist:
Use BAC's InstantDFM to verify they can produce your board within standard capabilities:
Impedance calculator:
Trace width calculator:
Manufacturing capabilities:
Stackup capabilities:
The section will go over setting up the tools for compiling firmware, the section will go over compiling the firmware, and the section will go over writing compiled code to hardware.
To use the container environment, you will need to install the or first. Podman is the fully open source alternative to Docker, and they share the same commands format. Either can be used, although most of this tutorial will use Podman because it is easier to use on Windows.
If your Windows 10 is Home version, you might not be able to enable Hyper-V. You should upgrade to Windows 10 Pro, or just use the free educational version from the school:
Follow the instruction on . You should install WSL 2. This tutorial is based on OpenSUSE, but it is possible to use other distros.
The toolchains repo has a readme with additonal information about the development environment.
To setup, install the extension in VS Code.
We use for libraries and a lot of the support code needed. The tools needed to run mbed are all included in the container. Run the commands below from the container prompt.
For most cases, you will only need the section.
For documentation on the Mbed API, look at the official docs . If you don't find a library for what you want there, look at community built libraries by searching using the search box in the upper right corner.
For more detailed documentation on Mbed Command Line Interface (CLI), look at the official docs .
While the mbed utilities can be used directly, most often in STAR we iterate on existing STAR projects. Therefore we have abstracted away most of the mbed commands using . Note that the specific build system can vary slightly from git repository (repo) to repository, so make sure to check the Readme of the specific project you are working on.
If you are unfamiliar with the Git version control system, check the out before continuing.
Linux: Install the stlink package from the package manager if available or compile from source .
How to debug hardware and firmware problems
Start with these steps to avoid common mistakes:
Make sure the PCB is powered (either by power supply or by battery). Indicator LEDs are generally helpful for this (if they were placed correctly).
Check for correct DC voltages with a multimeter at all input pins.
Check for continuity on nets. You can also inspect solder joints.
Check regulator outputs with a DC multimeter AND an oscilloscope.
Check input voltage at all ICs with both DC multimeter AND an oscilloscope.
Check for amplitude and frequency of all external oscillators with an oscilloscope.
Check bus signals with an oscilloscope.
After you determine that the PCB is powered correctly and connections are intact, see the firmware debugging to determine more complex problems.
Prior to checking firmware, make sure the hardware is functioning as expected using the hardware debugging steps.
Then,
Sanity check you can control GPIO pins by flashing a simple program that sets GPIO pins high, and another program that sets GPIO pins low. Check output using a multimeter.
Check the fuse bits are what you expect them to be.
Check the microcontroller is running at the rate you expect it to using UART. This may be a fuse bit issue as well.
Once you have confirmed basic control of the board and microcontroller, test your firmware by adding status LEDs to show general state of code (particularly useful to check control flow in a state machine). Add additional output at critical points in the code. Forms of output include GPIO pins, radio, UART, and LEDs. This should allow you to see where your program is going wrong.
Modularize the code as much as possible and test modules from simplest to most complex. Reduce complexity in the code.
Reviewing is one of the most important parts of bringing up a board – we don’t want to waste money or time on a flawed design. Consequently, it can take practice to really know what to look for while reviewing a board; there’s no substitute for watching an experienced engineer at work. However, most boards we make have quite a bit in common, so a lot of failure modes are also shared. For anything simple, the below guide should be a good starting point; for anything analog/RF, high-speed, or high voltage/power, additional care should be taken.
In general, when reviewing a board, make notes and open issues on whatever issue tracking system you’re using (GitHub, Jira, etc.). Let the responsible engineer (RE) review those issues and make changes – don’t make changes on your own. Especially with schematics, merging changes from multiple people can get messy.
Reviews take time to be done thoroughly, so (especially if a single person is doing the review), alot time in terms of days, not hours. Additionally, do not think of a review as a 'final check' before a board is put out for fabrication. It may take weeks to make changes and update until a board passes review.
Make sure you include the schematic file (and layout if applicable) as well as a bill of materials (BOM) that includes DigiKey part number (or Mouser #, or direct link if applicable), name, quantity, and price for literally everything on the board.
At the level of the board, one of the first steps is to ensure that all interfaces to other systems are met. This usually means that there should be power, a programming port (per MCU), and some combination of actuators + sensors + communication. Familiarize yourself with the function of the board within the system. The project page for the board or the system it is part of should contain the description of these functions against which you can compare the schematic.
Component level review should be exhaustive. This means pulling up a datasheet for every single component other than simple passives, and comparing side-by-side with the schematic. Things to look for:
Reference designs (in the datasheet) are followed
Directionality of I/O lines
Acceptable voltage ranges
Power lines
Every Vdd/GND pair should have a decoupling capacitor whose value matches what’s suggested in the datasheet
Analog power should be separated from digital power (sometimes with additional filtering on the analog lines).
Certain types of I/O (I2C buses, for example) require pull-up or pull-down resistors. If you’re not sure where these are required, ask.
Sometimes, components will have requirements on where they should be placed during layout (for example, decoupling caps should always be placed near the IC being decoupled). Make sure these are annotated on the schematic.
Lastly, at the system level, you should ensure that your power block can supply enough current/power to meet the peak needs of everything on the board, with overhead. Also ensure that top-level interfaces to other parts of the system are satisfied.
TBD
How to use the lab equipment
The power source is used in place of a battery when running hardware tests. You can connect this to your circuit by using banana plugs, pictured below. By convention, red should be connected to the (+) terminals, and black to the (-), or ground, terminals.
As described by the gif above, follow these steps to set up the power supply:
Turn on the power supply by pressing the Power on/off button.
Set a current limit. To set a current limit, first push the "Display Limit" button. Next, push the "Voltage/Current" button on the right of the machine so that the current is selected (blinking). Then, use the arrow buttons on the right to select the digit you want to adjust, and then use the knob to adjust the value of that digit. Generally, we will use 0.100A unless otherwise noted. While 0.100A may seem small, it is still enough current to cause serious damage to the PCB you're testing.
Select an output: This device is capable of outputting 3 different voltages with maximum values of 6V, 25V, and −25V respectively. Make sure to push the button for the output you would like to use.
Set the voltage: After selecting the correct output (step 3), set the voltage to the desired value. To do this, push the "Voltage/Current" button so that the voltage (displayed on the left) is selected (blinking). Then adjust the value using the arrow buttons and knob, like when you set the current limit. Make sure you are adjusting voltage and NOT current.
Turn the output on: By default, the output of the device is turned off. For the device to actually output current, press the "Output On/Off" button. Always turn the output OFF whenever you are idle / don't need the Power Supply!
Note that these probes have the same connector as the oscilloscope probes. But beware! The function generator and oscilloscope probes have different impedances, which means if you use the wrong probe for the instrument you're using, your output will give you absurd voltage values.
Multimeters can come handheld or in the lab as shown above. They are used to measure the resistance, current, or voltage difference across two terminals. They can also be used to test for continuity. This means that you can determine what points are shorted together or not. You can use banana plugs with this machine, but the probes shown below are generally better to touch at specific points.
Follow these steps to set up:
Turn the multimeter on.
Connect the probe to the multimeter. You can determine what terminals to plug the probes into by looking at their labels.
To measure voltage or resistance or to test for continuity, plug the red probe into the terminal with the V, Ω, and diode symbol.
To measure current, plug the red probe into the terminal with the capital "i" next to it.
The black probe should be in the terminal labeled "LO" between them.
Touch the ends of each probe to the nodes on the board that you want to measure across/test continuity for. You can toggle the information you want to see on the multimeter by pressing the DC V (for DC voltage), AC V (for AC voltage), Ω (for resistance), or cont ))) (for continuity) buttons. When you press cont, it will say open until it is shorted. If there is continuity, it will beep.
The oscilloscope can be used to measure signals that change over time. Unlike a voltmeter, which only shows the instantaneous voltage value, the oscilloscope shows a graph of voltage versus time, which is useful to see how devices respond to inputs. This piece of equipment may look pretty complicated, but most of the knobs are to adjust axes. Oscilloscopes can also be used to simply measure DC voltages, as one would with a voltmeter.
The oscilloscope probe that connects to the color-coded metal terminals at the bottom looks like this:
Follow these steps to set up:
Turn the oscilloscope on (button at the bottom left corner).
Connect the probe to one of the 4 input channels (yellow, green, blue, or red). Make sure that the channel is on (indicated by a green light on the channel number). To turn a channel on (when it was originally off), simply press the corresponding numbered button. To turn it off, push the button again, and the light will be off.
Connect your probe to your circuit.
Auto Scale: Potentially skip steps 5-7 by using the "Auto Scale" button (see the image above) to automatically scale the axes. Don't get too dependent on the "Auto Scale" button; sometimes it doesn't do a "good enough" job.
Adjust the horizontal axis of the plot. The large knob at the top (immediately to the right of the screen) controls the horizontal time axis and allows you to zoom in or out. The time increments represented by the tick marks on the plot are indicated at the top of the screen.
Adjust the vertical scale. The larger of the two knobs for each channel (the one above the button with the channel number) allows the vertical scale of the voltage graph to be adjusted. As with the horizontal scale, the number of volts per tick mark on the graph is marked at the top of the screen.
Adjust the offset. In some cases, signals will appear off-screen; adjusting the smaller of the two knobs (below the channel number button) corresponding to each input will shift signals up or down on the plot.
Add measurements such as average voltage, amplitude, etc. Measurements can be added by pushing the "Meas" button and using the buttons below the screen to select and add measurements.
The function generator can be used to provide test inputs to your circuits. It acts like a power source, but there is a difference. While the power supply is capable of giving you a fixed voltage, the function generator can output sine waves, square waves, and a variety of other waveforms that change over time. Sometimes the function generator is useful if more independent DC supply voltages are needed than the power supply can provide.
Steps to set up the function generator:
Connect the function generator probe (pictured above) to either channel 1 or 2.
Press the "1" button for channel one and the "2" button for channel two to see their menus. Here, you can set the output load (for example, high Z), voltage limits, as well as turning the output on and off (as you would with a power source).
Press the button labeled "waveforms" to get a list of waveforms. Press the blue buttons on the bottom to select your desired waveform.
Press the "parameters" buttons to set the parameters of your waveform. Here you can use the keypad, knob, and arrows to adjust the frequency, amplitude, offset, duty cycle, and phase of your waveform. Again, use the blue buttons at the bottoms to toggle between parameters. You can also press "units" to change the units.
How to code in C, given that you already have knowledge of other programming languages.
A useful reference linked here.
Primitive Data Types:
int
: integer
float
: floating-point number, used to store decimals.
double
: double-precision floating-point
char
: ASCII character
In the <stdint.h>
header, additional types are included for defining integers by size (in bits) and sign. A useful one is uint8_t
(an unsigned 8-bit integer type) to represent a byte.
Computers prefer to interpret things in binary, so the use of bit operators is often useful in C to more accurately visualize what happens underneath the abstraction. The most common operators are:
These don't seem super useful on the surface, but they will be once we start dealing with registers.
The microcontroller datasheet is your best friend!
I/O devices in a microcontroller (such as sensors or actuators) are mapped to memory addresses - that is, you can get a sensor value by reading from a location in memory, or modify an actuator output by writing to another location. What does this mean for you? Embedded C handles this through the use of registers. A register is a storage element in the processor, often used to hold intermediate values during computations. However, certain specialized registers are used to perform hardware functions, and we can access these registers by using their names.
For an example, let's look at the I2C interface on the Atmel ATMega328, a common microcontroller that is famously used on Arduinos. I2C designates a master and a slave device, and the master can individually address a slave device by sending its address on the common bus line before sending or receiving data. There is also a common clock line. Taking a look at page 292 of the datasheet, we find descriptions for each register used in I2C operation.
This register holds an 8-bit value that can be read from or written to (as we see from R/W in the access line), that determines the speed of the SCL line, which is the common I2C clock. The conversion of this value is as follows: SCL frequency = CPU clock frequency / (16 + (2 * TWBR * Prescaler)), where the prescaler is set in a different register.
Let's say I want an SCL frequency of 100 kHz from a CPU clock frequency of 16 MHz. I can achieve this with a prescaler of 1 and a TWBR of 72: 16 / (16 + 2 * 72 * 1) = 16 / 160 = 0.1 MHz. I can assign this TWBR rate simply like this:
So far, so good. Let's move on.
Whoa, okay. This one's a little trickier - we have two different values here. What should we do?
Let's go back to our bit operators from earlier. If I want to get only the TWI Status Bits (that is, TWSR[7:3]), I can simply right-shift the TWSR value to eliminate the three lowest-order bits.
What if I want to write to the prescaler bits without overriding a bit I shouldn't be writing? Technically, I can't override a read-only bit even if I try, but this will illustrate my point just fine. A useful feature of the OR operator is that if I OR something with a 0, I just get that same value - that is, A OR 0 = A. But A OR 1 = 1 no matter what A is.
Now consider this code:
What does this do? I'm ORing the TWSR value with a binary value that essentially passes the top six bits unchanged - since I'm ORing with zeroes. However, I'm forcing the bottom two bits to be 1s, because as I pointed out, 1 OR anything is 1. So this code forces the prescaler to 64, per the table above, but leaves the other bits unchanged! I can simplify this a bit:
This is great, but what if those prescaler bits are already 1s and I'd like to set them back to 0s? ORing won't help, because they'll be 1s after the OR as well. This is where the AND operator comes in handy. Note that for any A, A AND 0 = 0, but A AND 1 = A.
Now consider this code:
This is a similar trick. ANDing the top six bits with ones passes them unchanged, but ANDing the prescaler bits with zeroes forces them to zero. So the top six bits don't change, but the prescaler is now 1. Let's simplify this again:
Let's say now I want to make the prescaler 16, so I want to flip the single bit TWSR[1] to 1. Rather than typing out the binary mask I want to use, we can shortcut:
This left shift operator evaluates to 0b00000010, which is exactly the mask I wanted to use. Similarly, I can flip it back to zero with this:
This produces the mask 0b11111101.
Often, each bit in a register can signify different settings for the microcontroller, and is given a name.
In the I2C control register (TWCR), each bit (excluding bit 1) defines a setting of I2C. The datasheet defines the purpose of each bit. Below is the definition of bit 2, TWEN.
TWEN defines whether I2C is enabled or not. I can set this bit using the bit shifting, ANDing, ORing, and NOTing operations.
Using the predefined names makes the code easier to read and understand, and thus more maintainable, over using raw hex values.
And there you have it! You can use combinations of these tricks to do a lot of powerful things.
For a more complete reference on the C language, see the text below:
http://www.dipmat.univpm.it/~demeio/public/the_c_programming_language_2.pdf
This is a slightly more professional way to solder boards. Faster, but with some risk
Reflow Oven: essentially a toaster over that can follow a pre-programmed temperature profile
Solder paste: similar to solder, but comes in a syringe and is paste-like. When heated past a certain temperature, solder paste flows, and upon cooling forms an ordinary solder joint.
The Chenming Hu Innovation Lab (Supernode) contains a reflow oven. STAR as a team has used it successfully to solder components. Here is how to do so:
PCB to be soldered henceforth referred to as the "target PCB"
PCB blanks, preferably large and of the same height as the target PCB
Stencil (usually ordered from OSH Park)
Solder paste (63/37 Sn-Pb)
We currently have a syringe labeled CalSTAR in the Supernode refrigerator
This is expensive, so try not to waste it
Masking or other tapes
Scraper / credit-card-sized card
Clean the target PCB with isopropyl alcohol (isopropanol)
Arrange spare PCB blanks in a configuration around the target PCB as follows:
Make sure the PCB to solder is snug and there are no gaps around it. If the blanks are thinner (e.g. 31 mils) than the PCB to solder (e.g. 61 mils) or vice versa, you can double-stack. It is important to have the blanks be at the same height as the target PCB
Next, position the stencil such that the holes in the stencil line up perfectly with their respective pads
Once alignment has been achieved--and be sure that it's as close to perfect as possible--tape one edge only of the stencil to the blanks and orient it so the taped side is away from you:
Squeeze solder paste from the syringe "above" (tape side) each section of pads
You will likely have to add more solder paste after the first pass. It is OK to recover solder paste, move it around, etc., but be very careful not to scrape too much side-to-side or away from you. The stencil must remain flat and in position
Continue spreading the solder paste around until each pad clearly has solder paste on it. We have found a steep angle allows for the collection of paste from the top of the stencil, while a low angle and higher amounts of downward force can help to get paste through the holes in the stencil
Gently lift the stencil from the board and flip it "up", exposing the board
Using tweezers, carefully place all components according to the reference designators/layout.
After placement, verify each component is securely on the board by gently pressing down on the top of the package with tweezers
Remove the board gently from the blanks, without tilting it overly
After placement, components should be somewhat attached to the board--the solder paste is sticky. All components should be aligned with their footprints.
It's finally time!
Before starting this section, open all windows in the vicinity of the oven. This process may produce unpleasant and carcinogenic odors.
Open the reflow oven and carefully set the board on the ceramic / kapton tape spacers. Do not place the board directly on the metal tray of the oven
Close the oven door
Turn the oven on with the switch on the back. You will have to walk around to the other side of the oven to access it
Select the pre-set reflow profile for 63/37 solder.
Start the heating sequence.
Even though the reflow oven will not quite be able to follow the profile specified, we have had no known problems with just letting it run--the temperatures reached are sufficient. Abort only if it is abundantly clear that the oven will not reach anywhere near the desired curve, and restart--if the oven starts from 50C, there should be no significant issues.
Allow the oven to cool, and carefully remove your newly-reflowed board after waiting a few minutes for it to cool down!
Inspect the board for any "tombstoning", shifted parts, failed connections, etc. Some amount of these are normal and can be reworked with the hot air rework station or soldering iron.
Inspect smaller connections under the microscope, and retouch if necessary with a soldering iron
Do not be alarmed if the board is slightly browned--it's been toasted, after all
About ham radio and how to get your license
Ever think about building your own radio? To talk to your friends across the county, the country, or around the globe? How about some astronauts on the ISS? Do you like the idea of bouncing radio waves off meteors or even the moon? Think you have what it takes to learn CW ("Morse code")? Amateur radio operators ("hams") do all this and more. By getting licensed with the FCC, you can join the ranks of 8 million radio amateurs in the U.S. Getting licensed allows you to:
Build and operate your own radio equipment
Transmit on radio frequencies (not channels) exclusive to radio amateurs
Transmit up to 1500W*
Experiment with new communication schemes
If you are enrolled in the decal, all of the following information should be provided to you in class or on piazza. There are three levels: technician, general, and extra. The steps for registering for a technician ham radio exam are as follows:
After selecting "individual" and "yes" to the first two questions, fill out all your information and submit.
Note that you will get your call sign after you have passed your exam.
Use a scraper or card to press firmly down on the stencil and spread solder paste, drawing the scraper toward you. At no point should you scrape away from yourself, lifting the stencil!
Professor Miki Lustig often teaches a Ham Radio decal, along with his class EE123: Digital Signal Processing. You can check for information.
Register on the FCC website to get an FRN (FCC Registration Number). You will need this for all future ham exams. Click , then click "Register and receive your FRN."
While you wait to get your FRN, you can search for exams in your area by clicking . Note that there will probably be one in Berkeley at least once a semester. is what you should bring.
There are many resources on the ARRL website to study for the exam, such as the . However, seems to be the best place to do (many) practice exams.
Alka Seltzer Rockets are film canisters with 3D printed nose cones and fins, powered by Alka Seltzer tablets and water. Alka Seltzer is composed of sodium bicarbonate, citric acid, and acetylsalicylic acid (aspirin), which react when dissolved in water, creating carbon dioxide gas. This activity is designed for booths at Discovery Days.
For optimal results, add 3/4 of an alka seltzer tablet broken up into 4-5 pieces and add enough water to fill up the canister about 1/4 of the way.
Folder with nose cone and fin STL: https://drive.google.com/drive/folders/1hvyhlRqM5Wcn5oEIB2c1gB9fgIuNTpOw?usp=sharing
Alternatives to LiPo (Lithium Polymer) batteries that are suitable for high temperatures.
The maximum recommended/tested temperature for LiPo batteries is 60C [1].
When LiPo batteries operate at high temperatures, they are at risk of severe performance degradation, and produce gasses such as O2, CO2 and CO. This is because of the interactions at the electrolyte-electrode interface [1].
This has caused significant distress to our team, as we compete in New Mexico which routinely experiences extremely high temperatures.
Batteries better suited to high temperatures will have different internal chemistries that have high thermal stability. This is not a new problem and more suitable batteries do exist. A few have been listed here. More information will be added if we find reliable suppliers for these batteries and can try to work with them ourselves.
References
Straw rocketry is a simple activity involving construction of a simple paper rocket that can be launched with a straw. Students analyze the effect of different design parameters and environmental factors that affects launch distance. The activity takes about 30 minutes and is intended for an elementary school audience.
Slides:
Lesson Plan:
Templates:
Battery Type
Max Temperature
Potential Suppliers
Lithium Iron Phosphate (LiFePO)
200C [1], [2]
batteriesinaflash.com
Lithium Thionyl Chloride (LiSoCl2)
95C - 125C [3], [4]
Tadiran Eagle Picher
Jauch
Amazon?
We developed a coding workshop for Rainstorm Summer 2020 to teach high-schoolers about algorithms in a 25 minute session through zoom. This activity is designed for students with no previous experience with programming.
There are 3 variations to this activity: elementary school level for Scientific Adventures for Girls, high school level (25 minutes) for Rainstorm, and high school level (55 minutes) for Splash @ Berkeley.
Original agenda:
Python file:
Original slide deck:
Follow English conventions unless told otherwise
Leave names of existing places/companies/objects as is
ex. AT&T
Use the spellings/names of objects common in the US as opposed to those common internationally
ex. Labor vs Labour
Do not put a period after units unless other conventions dictate it
in, not in. or inches
3 ft, not 3'
30 mi/hr, not mph
4 hrs, not 4 hr
Nosecone is one word; not "nose cone"
Do not abbreviate words with symbols
ex. &, @
Capitalize proper nouns, but not regular ones.
ex. Nomex and Lexan, polycarbonate, payload, ejection subsystem
Replace words like 'Payload, Ejection, Movement' with phrases like 'payload system, ejection subsystem, movement subsystem' respectively.
Convention is to not hyphenate between latin prefixes.
ex. subteam is correct vs sub-team
ex. subsystem is correct vs sub-system
A sentence that uses a listing system within it should:
have a colon before the listing begins;
have semicolons between parts, and;
use the ", and;" transition before the last item.
Use --- in LaTeX to get the long m-dash used to separate parts of sentences. -More from brunston
A quick activity designed for Scientific Adventures for Girls. Elementary schoolers learn how to fold paper airplanes and various techniques to fold airplanes with different properties. The paper airplanes are modified with paper clips and hot glue to be compatible with the launchers. The launchers are laser cut from 1/4" plywood and 2 rubber bands tied in series.
Basic paper airplane designs: https://www.foldnfly.com/1.html https://www.foldnfly.com/23.html#Zip-Dart http://www.amazingpaperairplanes.com/special-FoldingShuttle.html
File for the launcher handle: https://drive.google.com/open?id=1-xcIQ6RzBKBEgQfNm30i7Ea8DOYpTp_r
For laser cutting in a hurry, try the Quick Cut or Quicker Cut versions. Quick cut: https://drive.google.com/open?id=1JfvUeSJ1fXi0T_x_kQmykSvNxs_Vm_rT Quicker cut: https://drive.google.com/open?id=1TngAumQyYzIghxUJ6bFFs_RGLtvzxjpJ
Guidelines for how to keep CAD documentation consistent within STAR
Conventions for CAD documentation of parts designed for use by STAR can be grouped into 2 categories: drawing setup and filename conventions.
Regarding drawing setup, CADs for the purpose of documentation should use the drawing template and use Imperial (also known as IPS) units. Furthermore sub-assemblies should be placed in external files (a tutorial of how to do this is soon to come).
Regarding filename conventions, file names of CADs should adhere to the following guidelines:
File names shall follow the general convention of: Project_Subteam_DescriptiveName[_McMaster part #]. See below for project and subteam codes.
An example of this might be IREC20_PAY_Payload_Centering_Ring.SLDPRT for an in-house part or IREC20_AIR_Weld_Nut_90611A320.SLDPRT for a McMaster part.
Similarly an example for an assembly might be IREC20_AIR_Nosecone_Assembly.SLDASM
File names shall not contain special characters (e.g. "!@#$%^&*()?/|\" ) aside from "_". Hyphens shall be allowed only if part of an external part number. Spaces and periods (outside of ".SLD***") are not permitted, as they can cause filepath issues.
Subteam shall be denoted by its appropriate 3-letter abbreviation:
AIR : Airframe
AVI : Avionics
PAY : Payload
REC : Recovery
PRO : Propulsion
SIM : Simulations
OUT : Outreach
Project shall be denoted by the selected abbreviation for the project:
MINDI: 2" minimum-diameter rocket
IREC20 : 6” diameter rocket design for IREC 2020 (this is Bear Force One, the project started before it was named and before IREC 2020 was moved to 2021)
LE165 : “Hot Take”, Propulsion’s first-iteration of a liquid engine
LE1: Liquid Engine 1, Propulsion's 2020-2021 "simple" engine
LE2: Liquid Engine 2, a multi-year project to design and build a higher-performance engine. Custom tank CAD can also use LE2.
SSEP: Stage separation demonstrator
DAVE: Deployable aerial vehicle experiment, a payload launching on Bear Force One.
CAS: Common Avionics System mission(s), flown on AirBears. AirBears (the vehicle) was developed before the naming convention became mandatory, but all CAS-related CAD should follow the convention.
It's pronounced "LAH-tech" or "LAY-tech", not "LAY-tecks"; the letters in TeX are meant to represent the Greek letters tau, epsilon, and chi.
is a typesetting system, much like Microsoft Word or Adobe InDesign. It is not a text editor. is used widely in the scientific and technical publishing industry; if you've seen a document that looks like the picture below, chances are it was written in .
While documents come in all sorts of flavors, they generally share a similar appearance because they use the Computer Modern typeface. However, all the fonts, colors, layouts and pretty much everything is customizable--is a way of "programming documents".
While Microsoft Word is a "What You See Is What You Get" (WYSIWYG) system, is decidedly not. Instead, is written as code (see below), and then compiled, usually into a PDF.
The most common reason to use is because you are writing a document with equations in it. There is simply no other way to get beautifully formatted equations (although many programs like Word now support syntax).
Even if you don't have equations, allows writers to stop worrying about annoying formatting issues, breaking their document when they add a picture, etc. and focus on the actual content. Documents like reports and books can be written in sections and seamlessly re-compiled using the article
andbook
classes, while the formatting and numbering of tables, figures, references, citations, footnotes, etc. are taken care of completely automatically.
To give one example, if you have 5 figures labeled Fig. 1 through Fig. 5, you can insert a figure between Fig. 1 and Fig 2. and not have to worry about changing the references to Figs. 2-5 to Figs. 3-6. This can save an enormous amount of time when writing longer documents.
There are two ways to use : locally on your computer or in the *cloud*.
This is really for hardcore users and people without internet. You'll first need to install a version of compatible with your operating system. Head over to https://www.latex-project.org/get/ to get started; we recommed TeX Live for Linux, MacTeX for macOS, and MiKTeX for Windows. These downloads can be pretty big!
As mentioned previously, is a typesetting system, not an editor. You can write documents in Atom, Sublime, Notepad, Notepad++, vim, Emacs, ex, TextEdit, or whatever text editor you can get your hands on. That being said, TeXnicCenter and TeXstudio are popular editors for Windows, and MacTeX includes TeXShop; you might want to use these or similar TeX-oriented editors to edit your documents unless you know what you're doing. Linux users can choose from 10s of options; for some reason people who are into Linux are also into TeX.
Welcome to the future. Simply head over to https://www.overleaf.com/ (now merged with ShareLaTeX) to get started! UC Berkeley provides free Overleaf Professional with a verified berkeley.edu email address. Overleaf has hundreds of great templates and tutorials to help you get started.
While there are hundreds of tutorials on the internet, this one is pretty good: https://www.overleaf.com/learn/latex/Learn_LaTeX_in_30_minutes. When in doubt, just Google! Chances are someone's had the same question and made a StackOverflow post about it.
We have previously used to compile our reports for NASA Student Launch. If you ever need to make a checklist, design document, or report, feel free to use . Generally, Google Docs is a little easier for the uninitiated, but don't be afraid to make your documents look nice!
Tutorials specific for the Payload subteam. Since the payload team is quite broad, the most important tutorials are those referenced under General or Manufacturing.
Most of the tutorials under Manufacturing have been written by Payload members for Payload applications:
Installing and using KiCAD for editing schematics, layouts, symbols, and footprints.
Download KiCad from here: http://kicad-pcb.org/download/
This also contains instructions for each system.
The KiCad tutorial is actually pretty good, so in general refer to it. The Avionics intro project (on Gitbooks) guide also walks through usage of KiCad.
To jump right in, go to Draw Electronic Schematics and then Layout Printed Circuit Boards.
Use the following link to learn how to make new symbols for components when you can't find an existing symbol for it in the KiCad libraries.
Often, it can be worth finding an existing symbol that is similar (for example, an older version of a sensor), copying it, and modifying it.
Try to make symbols following a functional pattern of placing pins. Symbols don't need to look like the footprint of an IC. Often, symbols of ICs will have all Vdds/Vccs/Vddios at the top, all Vss's at the bottom, and pins on the sides of the symbol.
STAR has has a repository hardware-sch-blocks
which contains a library of symbols, star-common-lib
. Create your symbols in this repository on a new branch, add them to the library, and when ready submit a pull-request. Make sure to update the datasheet link and description!
If you've made your own schematic symbol for a component, you will likely have to make a footprint for it as well. Footprints are described here. The following link will show you how to make new component footprints.
As with schematic symbols, try finding an existing footprint and then modifying it according to the actual component's datasheet. Datasheets will have drawings and dimensions of the footprint, often under a section such as 'Packaging'.
Many ICs come in standard packages (such as SOT-8). KiCad includes footprints for these standard packages, so often one can select one of these and then ensure with the datasheet that it matches--unfortunately, different manufacturers may use the same name but actually have slightly different footprints.
As with symbols, all STAR footprints go in star-common-lib
in hardware-sch-blocks
. Create your footprints on a new branch (makes sense to put them on the same branch as the new symbols), and submit a pull-request. Please let the current Avionics lead know when you submit a pull-request so it doesn't slip through their email.
CalSTAR Composites Best Practices
This technical note condenses practical knowledge about producing composite parts from the CalSTAR team and alumni. Focus is on materials and best practices: what to use, where to get it, and how to use it. This document is not a replacement for hands-on practice and self-driven learning, but it should give newer team members a good head start.
Unlike a typical engineering note, this document is a living article with no restricted author list and no formal revision structure. Therefore, when editing, please be concise, neutral, and specific. This document is a forum for imparting hard-won composites knowledge, rather than hard-won personal philosophy. With the exception of diatribes against Bondo. These are fair game.
Use good safety practices (gloves, goggles, avoid skin contact, ingestion, inhalation, etc) with all resins and materials described below. Read the MSDS and be aware of safe disposal methods as well as safe use. This document makes no attempt at a complete description of safe handling or risks of the materials described. Some particular examples of the safety precautions to be aware of are:
Again, it is essential to properly research for yourself the risks and best safety practices for each material and process before use. If you are unsure, it is always better to contact a lead and ask for assistance than to endanger yourself.
Resins are usually used with a reinforcing fiber or filler. Common resins fall into the categories of epoxies, polyesters, vinyl esters, and cyanate esters. Most layups generally use:
Cyanate esters behave similarly to epoxies, and are the most common resin system for prepreg.
Understand that all vinyl esters and polyesters require fitted working respirators, to avoid breathing in the solvents, this should be done with zero ex
Also understand that vinyl esters and polyesters should only be used in conditions with good ventilation and no spark / fire hazard, as the aerosols are flammable.
Many dusts and fillers are bad to breathe -- when in doubt wear a dust mask.
If material like a resin gets on the skin, it is usually incorrect to attempt to “wash” it off with a solvent. The reasoning is that the solvent will simply dissolve the material and make it easier to penetrate the skin! Use soap and water with manual scrubbing instead.
epoxy as the matrix for fiber-reinforced laminates
vinyl ester as the matrix for fiberglass molds
polyester (e.g. gel coat) as the hard surface coat for molds – if molds are used.
These resins are all thermosets. In other words, the curing process is a 3D chemical cross-linking, where the mers (short CH molecules of which the resin is composed) grow strong links to one another. The process is both heat-driven and exothermic, so it accelerates itself. This means two things:
You can speed up a cure by heating the resin.
Thinly spread resin (volume / surface area = low) will cure much more slowly than a mass of resin in a container (volume / surface area = high).
With regard to point (2), a large mass of curing resin left in a cup will often turn brown, smoke, and put off foul smells and lots of heat. (The self-accelerating effect is compounded by the fact that polymers have low thermal conductivities, so the heat cannot escape the curing resin easily.) Therefore always dispose of excess resin by spreading it over a large area of paper or plastic, and letting it cure in that spread-out state.
The 105 epoxy system is the default for laminated parts. Various hardeners can be combined with 105 resin to adjust cure time and cured part properties. Usually the 209 hardener is chosen, which gives a long pot life, so that the layup will not be rushed. The 105 system features a low viscosity, making it a good laminating resin. The main downside of the 105 system is its low Tg (~120°F).
9396 is one of the stiffest and most temperature-resilient (service temperature up to 350°F) structural epoxies. It is more difficult to use in laminations due to having a higher viscosity and shorter pot life than West System 105/209. (However, the team has made many successful laminations with 9396.) It can be used as a good adhesive, and is the best option for laminates or bonds in close proximity to intense heat sources (like the exhaust). 9396 is effective as a potting and repair resin. Expect working life on the order of 1.5 hours, and at room temperature, 70% cure in 24 hours, with full cure in several days. At elevated temperature (~135°F), cure time can be significantly reduced to ~1.5 hours.
Tap’s 4:1 epoxy is moderately stiff and strong. It has the benefit of being readily purchased on short notice, and can be used for general purpose potting and lamination. However, as a general purpose resin it makes significant compromises: it has a higher viscosity than 105 and a shorter pot life than both 105 and 9396. Expect a working life of less than 15 minutes.
The team has usually used Tap’s polyester resin, and found it serviceable. Polyester alone can be used as a matrix for fiberglass molds, and finds few other applications. In fact, other Berkeley teams have frequently used vinyl ester instead of polyester for fiberglass molds, since the vinyl ester is more thermally stable and bonds better to epoxy than polyester.
A polyester product called “gel coat” comes pre-filled with talc, CaCO₃, and other mineral oxides so that it can produce a thin, hard surface layer in molds. Tap’s gel coat has most frequently been used by the team for fiberglass molds. For surfacing of urethane foam plugs, a similar product called Duratec is probably superior in hardness and in holding a smooth surface during sanding; in a pinch gel coat on urethane may suffice.
Vinyl ester is very similar to polyester in processing behavior. It is somewhat more expensive than polyester, but deforms less under temperature and bonds well to both polyester and epoxy. Vinyl ester is the usual choice of matrix for fiberglass molds – this because fiberglass can be more demanding of a perfect medium for a usable quality layup. Tap’s vinyl ester product has generally been used.
Cyanate ester is the most common resin system for prepregs (frozen fiber tapes pre-impregnated with resin). Once cured, it is mechanically similar to epoxy, but has better resistance to hot-wet conditions. In the uncured state it is very sensitive to moisture. When removing prepreg from the freezer, where it should be stored prior, it must be allowed to come to room temperature before opening the bag. Otherwise condensation on the material will ruin it. When repacking prepreg for putting back into the freezer, include a dessicant pack and seal the bag well. Cyanate ester systems require heat to properly cure. Most of the prepreg we will likely use is RS3, and cures when held at 350°F for several hours. There are published schedules of heat and pressure to define good cure cycles for various resin systems.
For the most part, the team has used high-strength carbon fibers such as AS4 and IM7. These have relatively low modulus and fall into the “black aluminum” design regime. A key decision when acquiring fiber is the form of the fabric: whether to get unidirectional or woven, and if woven, what type of weave. It has been useful to get a moderate amount of unidirectional material for making strength-controlled shear panels, but for the majority of parts that are not filament wound, we will use woven cloth.
Satin or twill weaves are much easier to control during layup than plain weave. Plain weave is very difficult to use in any part with bi-directional curvature or uni-directional curvature tighter than ~200 mm radius. Therefore it is advisable to always insist on 5 harness satin or twill. Fiber areal weight of ~6 oz/yd² is generally useful. In special applications, lighter fabrics may be desirable.
Carbon fiber composites have good electrical conductivity in the plane of the laminate, but if using the carbon for example as a grounding body, it is necessary to drill into it and install a metal stud which will bypass the current past the surface epoxy (which is non-conductive) and into the center of the laminate, where contact can be made with the exposed carbon fibers. Carbon fabrics are easily cut with good, sharp shears.
By experimentation, we have found that plain weave final product should be around 0.35-0.36 g per square inch.
The usual glass in fiberglass fabrics is E-glass, which is strong and moderately stiff. Fiberglass is good as a thermal and electrical insulator and is reasonably strong, but significantly heavier and less stiff than carbon. Many weights of cloth are available depending on the application. Usually a fiberglass mold is made using glass mat and vinyl ester resin; however, in the case of an epoxy-glass mold, one would use a woven glass fabric. Glass fabrics are easily cut with good shears.
Aramids (commonly referred to by the brand name “Kevlar”) are strong in tension and moderately stiff. They have extremely poor strength in compression, but extremely high strength in shear. They are therefore used where skid-protection or shrapnel containment is necessary. They find some use in the lining of section of rocket airframe where catastrophic failure which may result in shrapnel may be present. Aramids are difficult to cut in the dry state and difficult to cleanly trim or machine when cured in a matrix. In the dry state, the best method of cutting is with well-sharpened high-quality shears, and patience.
The team has experimented before with fabrics that combine both carbon and aramid fibers in the weave. Generally this hasn’t been found particularly useful, as the aramids reduce the overall stiffness and compressive strength without adding any benefit that couldn’t be otherwise more efficiently achieved by including a separate aramid layer in the stackup.
Glass fibers and carbon fibers are also produced in mat form, where the fibers are randomly oriented and loosely packed together. The fibers are lightly bound to each other by a “size” adhesive, which dissolves in the resin upon lamination. Glass mat fibers typically have a size which is soluble in polyester and vinyl ester, but has poor solubility in epoxy. Carbon mats usually get a size which has better solubility in epoxy. But the type of size can only be definitely ascertained by contacting the manufacturer. Glass mat in heavier weights (1.5+ oz/yd²) is predominantly used in combination with vinyl ester when making fiberglass molds. In low weights, glass and carbon mats are usually called “tissues” or “surfacing veils”, and are useful when a very smooth surface is required on a part without the use of gel coat. As an example, an 0.7 oz/yd² glass surfacing veil has been used for the interior surface of the restrictor; weights down to 0.3 oz/yd² are readily available.
There is not much "theory" to selection of weave in typical rocketry usage. One usually wants twill or satin weave, and not plain. Plain weave is difficult to use on anything other than flat plates or large cylinders. Twill or satin will conform to bi-directional curves much better. Satin is most generally useful, especially in harnesses 5HS to 8HS. The tow count -- 1k, 3k, etc -- often seen associated with a weave is the number of fiber strands in each tow of the weave (a tow is a single fiber bundle -- multiple tows are woven to form a weave). So the tow count is directly related to the fiber areal weight. (Fiber areal weight -- FAW -- is the mass of fiber per unit area, usually quoted in oz/yd² or g/m². The unit g/m² is often written “gsm”.)
Fumed silica (also known by brand name “cab-o-sil”) is a filler powder used to thicken epoxy resins. It is lightweight and confers thixotropic (shear thickening) properties on the resin, making it very useful in all potting, filling, and surfacing applications. Epoxy filled with fumed silica creates a hard, sandable surface. Sometimes microballoons are added to either reduce weight or weaken the surface (to make sanding a little easier).
Glass microballoons are a powder consisting of small hollow glass spheres. The hollowness makes them extremely lightweight. They are useful in potting applications where weight minimization is important. Microballoons are not as strong as fumed silica, and do not thicken the resin as effectively, therefore they are often used in combination with fumed silica.
Talc powder (a magnesium silicate) can be used as an epoxy filler. It is heavier than fumed silica and makes a surface which can be very difficult to sand. Therefore, it is not commonly used in applications where a surface finish is desired. However, it does improve smoothness of the filled resin, so sometimes a small amount of talc may be added in a surfacing application.
Milled or chopped glass fibers are readily available. They are simply E-glass fibers which have been cut to very short lengths. Milled fibers are short enough to look like powder, but will significantly strengthen the resin when used as a filler (at a cost of more weight). Chopped fibers are usually ⅛” to ¼” long, and greatly strengthen the resin, but it is difficult to spread a resin smoothly when filled with chopped fibers. Therefore, milled fibers are more often useful, particularly as an additive in mold surfacing when high strength is required (at the cost of more sanding time). The CalSTAR team has utilized this in the past by impregnating JB weld adhesive with Carbon Fiber shavings.
Chopped carbon fibers are usually produced by the team, simply by repeatedly cutting scrap carbon fabric. They are useful for rapid repair in potting and filling applications. When onsite during a test or launch day, it is useful to have on hand a quantity of chopped carbon and fast-curing epoxy, to rapidly mix up a high-strength potting compound to apply to fill damaged areas which will cure within a short time period. Resin filled with chopped carbon can be difficult and messy to control, as the fibers tend to clump together and not flow.
Bondo is a well-known material among hobbyists and amateurs. It is notable for being weak, brittle, and difficult to control. In particular, its cure time and hardness is highly sensitive to mix ratio with the catalyst. When applied as a filler to a mold surface, the Bondo is much weaker than the rest of the surface; this discontinuity in strengths makes it difficult to achieve a smooth and continuous surface during sanding. Bondo is composed of a polyester resin with a weak filler powder, and will dissolve styrene foams. No one knows precisely why Bondo remains popular, but year after year its ill-advised usage has punished the production schedule of many rocketry and other competition teams alike. It is strongly recommended that Bondo not be used.
Special dispensation is made for a particular Bondo product called “Professional Glazing & Spot Putty”. It has a finer grained filler than general Bondo, and can be useful in the single specific case where one wants to fill tiny pinholes in mold surfaces -- in this case the goal is explicitly to have a weak filling agent, so that any excess filler remaining on the surface surrounding the hole can be easily sanded off later with a fine paper, and not risk damaging or mis-shaping the rest of the surface. A common mistake is to forget that the filler is a two-part system: it must be mixed with a hardening catalyst in order to cure. UV-curing putty is available, but it can be difficult to achieve full and consistent cure; therefore, the UV-curing material is also not recommended.
Urethane foam is the standard for mold making. In general, the higher the density, the better will be the mold. Cost scales directly with density; there are trade-offs to be made. Typical densities availale are 6, 10, 20 lb/ft^3. High quality parts have been made with 6 lb/ft^3 foam, but 10 or greater is preferred, as it will improve fidelity and reduce the coating/sanding effort considerably.
Urethane foam sands well and is reasonably strong. In lower density (6 lb/ft^3) take care not to puncture the foam, as its compressive strength isn’t too high. The foam is somewhat brittle and should not be dropped from too high or danced upon too enthusiastically. Urethane foam is compatible with both epoxy and ester resins. Slabs may be bonded together with either of these agents, or urethane Liquid Nails, or Gorilla Glue. When bonding slabs, make the adhesive layer as thin as possible -- otherwise it will be a hardness discontinuity that interferes with machining/sanding.
Polystyrene foams are cheap and readily available. They usually come in 1” thick boards meant for building insulation, but can be sometimes purchased thicker. There are two basic types:
● Expanded polystyrene (EPS)
● Extruded polystyrene (XPS)
EPS is composed of many beads fused together, and is horrible to sand / mill / shape. It is usually white, and often used in molded shipping boxes or packing peanuts. XPS is much better for sanding and shaping, and comes in colors blue or pink (there is no significant difference between XPS in the two different colors). Both typically come in 1-2 lb/ft^3 density: very light and very low hardness.
Over the years, polystyrene has been used to make a number of molds for FSAE and CalSol, two other competition teams on campus. These generally have been of low quality and time-consuming to produce. Polystyrene has the twin disadvantages of being very difficult to sand smooth, while also being incompatible with all polyester resins / fillers (these resins include styrene monomers in their formulation -- clearly, then they will dissolve styrene foam).
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For the most part, one uses special epoxy formulations for adhering composite parts.
9309 is a high-strength structural epoxy adhesive. It is similar in many respects to 9396, but has a special filler allowing it to bridge gaps up to 0.030” and create good fillets with honeycomb core. It has a lower glass transition temperature than 9396, therefore it can be debonded with a heated blade when necessary. One generally does not add extra fillers to 9309. It has a Tg = 130°F and service temperature up to 160°F.
DP4X0 is a high-strength epoxy adhesive with a minute pot life indicated by the value of x and 24 hrs to full cure. Pot life options include 20 minutes, 60 minutes and 90 minutes. Recommended for all general purpose bonding when fast cure time is desired. Excellent for trackside repairs. While it can be filled with milled or chopped fibers to increase strength of a repair patch, this may make it brittle and thus more prone to failure. It also comes in a "NS" or "non-sag" variant which is good for applications such as creating fin fillets.
9396 is discussed earlier in this document as a laminating and potting resin, but is repeated here. It is specifically useful as an adhesive in high-temperature locations (service temperature up to 350°F). It can be moderately filled with fumed silica to bridge bond gaps between 0.020” - 0.030”, and needs no filler at gaps less than 0.015”. Because 9396 is quite linearly rigid, a good bond joint design becomes more important wherever peel failure is a concern. As one of the stiffest resins available, with reasonably low viscosity, 9396 is particularly good as an adhesive whenever the primary design requirement is stiffness and a definite 0.005” - 0.008” bond gap can be obtained.
Decent results can be achieved with adhesive epoxies available from hardware stores. Devcon brand epoxies have been used successfully and are recommended. However, 9309 or DP420 will still be superior in strength, stiffness, and repeatability.
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Shears are not scissors. Shears look like big scissors, but they’re better. Good shears are sometimes marketed as carpet and upholstery shears. They have an adjustable pivot screw to control pressure between the two blades. The blades are of alloy steel and hold an edge. Shears need to be sharpened from time to time. Correct sharpening technique is essential to maintain close contact between the two shearing edges. An example of good shears is shown from the MSC catalog below.
The most effective saws for cutting fiber composites tend to be toothless steel disks impregnated with diamond powder. These are commonly available, marketed as tile-cutting saws. They can be purchased in sizes which fit Dremels, grinders, tables, etc.
High-speed steel drill bits will go dull fairly quickly when cutting fiber composites. Cheap ones can be sacrificed for simply punching holes. Machinists will not thank you for using their good precision drills to cut composites. Carbide bits are preferred, as they will last longer and cut cleaner. High precision (diameter tolerance < 0.001”) holes are readily achievable in composites with carbide reamers.
If a composite part is to be cut or shaped in a mill or router, the cutter should preferably be carbide, with a titanium nitride coating. Again, machinists will not thank you for dulling down their general-purpose high-speed steel cutters on composites. Sacrificial bits may be used to ease their pain with prior request to the team.
A standard stock of sand paper includes 60, 100, and 200 grits in dry sanding paper; 100, 200, 400, 600, 800, 1200 in wet sanding paper. Higher grits go dull quickly; in any grit, the paper must be replaced with some frequency as it goes dull. Discard dull paper -- this is not the place to be miserly.
Scotch-brite pads come color-coded in different levels of aggressiveness of abrasion. It is usual to keep a stock of green pads (aggressive) and light gray pads (very soft). Note that some other colors of scotch brite are “tan”, “gray”, and “dark gray” -- not to be confused with “light gray”, which is almost white in color. Like sand paper, scotch-brite goes dull with continued use, and should be discarded.
Single edge razor blades find innumerable uses in composites manufacture. They are cheap and disposable. It is usually worth the extra money to get precision edge stainless blades, which will hold an edge sharper and longer than the standard blades. Blades should be disposed of frequently as they go dull. Proper disposal requires a sharps box of some sort.
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Before bonding two surfaces together, it is critical that they be properly prepared. The goal is to achieve three qualities:
Cleanness -- no interfering grit or organic particles
High surface area -- increase surface area with texture
High surface energy -- increase the molecular adhesion between the surface and the glue
When bonding a fiber composite surface, the goal is to achieve scratches in all directions in the plastic matrix only. Carbon fibers, in particular, are poor bond surfaces, therefore one does not want to sand into the fiber. (If you see black grit, you’ve gone too deep.) Green scotch-brite pads are an effective abrasive to achieve scratches in the matrix without attacking the fibers underneath. Scratch the surface thoroughly in all directions, either with swirling motions ~1” in diameter, or by scratching at 0°, 90°, +45°, -45° in succession.
When bonding a metal surface, sand paper may be necessary to achieve good scratching. 200 grit dry sanding is effective, again moving either in 1” swirls or a 0°, 90°, +45°, -45° succession of sanding directions.
Clean the surface well with degreaser and water, then isopropyl alcohol. For stubborn surfaces, acetone may be necessary, always check to ensure that the surface is acetone safe before using acetone.
Prior to bonding, the quality of the surfaces can be tested by putting a few droplets of water on them. If the water spreads out into a thin film, then the surface energy of the part well exceeds the surface tension of the water. This is a good sign, indicating that high surface energy has been achieved, and the bond will be good. If the water balls up, repelled from the surface, then the surface prep steps must be repeated.
Bare aluminum in air rapidly forms an oxide layer which bonds poorly. However, if this natural oxide layer is replaced with a special chromate one, the aluminum-to-epoxy bonds is one of the strongest you can get. Therefore, after mechanical abrasion and cleaning, the aluminum is to be etched with West System 860. While still wet after etching, the second part of the 860 system is applied, which puts down a chromate layer. This protects the aluminum surface from oxidation for several hours. In this time window, the bond should be made. A respirator with good filters is recommended while applying the chromate.
Note that anodized aluminum is a very poor bonding surface, and should be completely removed. This can be time consuming.
Also note that there is a more permanent alternative to West System 860, called “iridite” or “alodine”. This surface coating makes for excellent bonds, and does not have the same restriction on time frame for bonding. (The alodined surface is good for adhering to paint as well as epoxies.)
When the goal is to have a material not stick to a surface (i.e. a plug or mold), it is again critical that the surface be properly prepared. The goal is to achieve three qualities:
Cleanness -- no interfering grit or sticky particles
Low surface area -- keep the surface as smooth as possible, i.e. a mirror-finish
Low surface energy -- decrease the molecular adhesion to the surface
Flash from previous uses of the mold should they be present, should be mechanically removed. A soft scotch-brite pad (light gray) is helpful. Be sure not to scratch the mold. If aggressive cleaning is necessary, use a degreaser with water, then acetone. Otherwise use isopropyl alcohol with a towel. Blow off dust and repeat wipe-down until thoroughly cleaned.
In situations where a mold is not used, but you are interfacing a carbon fiber layup with a surface which eventually you do not want the carbon to be bonded to, following the same steps as above but replacing the mold with your surface. Remember that it is always better to be sure of what you’re doing but slower than to work quickly and risk damaging or destroying the surface.
Use Meguiar’s mold release wax or Part-all paste wax. Apply a thin light layer over the whole surface with a microfiber towel. Let the solvents flash off 5 minutes, then buff in the wax until shiny with a clean microfiber. (Buffing well is important -- a shiny waxed surface will release well, whereas a hazy texture of wax can actually act as a mild adhesive!) Repeat a minimum of 3 coats. The mold release wax provides a strong, low surface energy barrier between the mold and the part. It fills and smooths pinholes and tiny scratches. Often, mold release wax only needs to be applied the first few times a mold is used -- after that, the mold becomes “seasoned”, with plenty of wax permanently impregnated into the surface.
Before applying mold release film, but after waxing, the quality of the release surface can be roughly observed by putting a few droplets of water on the surface. If the water balls up, then the surface tension of the water exceeds the surface energy of the mold. This is a good sign, indicating low surface energy has been achieved on the mold, and it should release well. If the water spreads out in a thin film, this means the surface must be improved, either by better waxing or (more likely) by stripping off the wax (with acetone) and sanding the surface smoother, then clean it again and re-wax.
Mold release film is applied every time a mold is used. It is applied as a thin liquid layer which hardens into a polymer film no more than a few microns thick. It provides a breakable layer and a geometric offset between the mold surface and the part, allowing for easier release. Dampen a towel with mold release and wipe on a single layer covering the full surface. Rewiping over an area will only dissolve the previous release and is therefore unnecessary, but not harmful. Again, understand that the mold release film is a very thin coat.
In a typical application, where a male plug is to be made, and then a female mold produced off of the plug, the essential steps are:
Urethane foam slabs are bonded together into a larger block
The foam is machined by a CNC routing shop off of CAD geometry
The machined plug is sprayed with a polyester-based hard surface coat (e.g. Duratec or Gel-Coat)
The coated plug is sanded smooth and polished
The female fiberglass mold is laid up on the plug
For a nosecone of size, say, 13” in diameter, expect step (1) to take two person-days, step (3) to take two person-days, and step (4) to take six person-days. The schedule for step (2) depends on how quickly you can get the CNC shop to mill the foam and send it back. Making the female mold (step 5) is discussed separately in this document. The bottom line to be very aware of is to start early! The time estimates above are deceiving, because:
● These estimates are for experienced workers. Students new to the process will be slower, with greater risk of damaging plugs and then needing to repair them.
● All curing processes have inherent downtime while you wait for resins to harden. This compounds the time cost of any unexpected repairs.
● The other time constraints on student schedules -- you really need full workdays to be most effective, and these only happen twice a week.
It is worth checking the mass of a given foam plug in CAD, to understand how many people will be needed to move it around as it goes through the various processing steps.
MORE DETAIL TO-DO
The following outlines the process for making a 2-part fiberglass mold
Necessary Supplies:
● ⅛” Particle Board
● Thick Fiberglass Mat
● Vinyl Ester Resin / MEKP Catalyst
● Oil Based Clay
● Hot glue gun
● 2-3” paint brushes
● Plastic hemispheres
● Gel coat
Outline of steps:
Build dam separating the two halves of the mold
Gel goat first side
Lay-up fiberglass on first side
Tear down dam
Gel coat second side
Lay-up fiberglass on second side
Pull mold off plug
Outline of steps:
Prepare mold
Prepare materials: carbon plies, peel ply, breather, dropcloth, vacuum bag
Wet the carbon
SafeLease the mold
Lay up on mold surface
Vacuum seal part and vacuum part
Cure
Remove part from mold
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Some useful books and articles are compiled in the table below.
This is a rough and incomplete list of composites-specific suppliers that may be used.
Title
Author
Where to find
Comments
ME127 reader: Design and Manufacture with Composite Materials
Multiple, compiled by Prof. Dharan
Needs to be Sourced
Concisely combines information from various textbooks and guides into one composites bible
Fiberglass and Composite Materials: an enthusiast’s guide
Forbes Aird
Purchase if need be – pdf is being sourced
Straightforward, covers all the basics in resins, fabrics, layups, tools, processes
Surface preparations for ensuring that the glue will stick in bonded composite structures
L.J. Hart-Smith
Search engineering articles database
Essential reading on bond prep of surfaces
Adhesively bonded joints for fibrous composite structures
L.J. Hart-Smith
Search engineering articles database
Essential reading on bond joint design and why bonds fail
Mil Handbook 17-2:
POLYMER MATRIX COMPOSITES
MATERIALS PROPERTIES
US Dept of Defense
Extensive list of tested material properties for various fibers and resins
Mil Handbook 17-3:
POLYMER MATRIX COMPOSITES
MATERIALS USAGE, DESIGN, AND ANALYSIS
US Dept of Defense
Overview of most practical composites matters. Most common standard reference in composites world
Handbook of Composites
edited by S.T. Peters
Good combination of theory and practical knowledge
Principles of Composite Material Mechanics
Ronald F. Gibson
at engineering library
Current ME 127 textbook, lots of theory
Tensile Properties of Glass Microballoon- Epoxy Resin Syntactic Foams
Nikhil Gupta and Ruslan Nagorny
Properties of epoxy-glass microballoon potting compounds
Supplier
Location
Link
Comments
Tap Plastics
Stores throughout Bay Area, one close to garage
Close to RFS, fairly limited selection
The Composites Store
Southern California
ACP Composites
Livermore
Douglas & Sturgess
Richmond, close to garage
Setting up ground station software to run on laptop
First, install npm
. Then, run $ npm install
. This will take a while as there are many dependencies for the ground station software.
If your terminal fails on
try uninstalling and reinstalling node.js.
If you are getting a git error such as
try running npm cache clear
.
If you are on Windows and are installing npm
in WSL, npm
will likely fail if you have npm
also installed in Windows itself. Install npm
in only one of the two.
To run the program, you will first have to plug in the ground station and then determine which device the ground station is.
On Windows, open Device Manager
, look under COM Ports
. Remember which are listed, and then unplug ground station. The Device Manager will refresh and, if the ground station was correctly detected by Windows, one of them will have disappeared. You can plug ground station back in for it to reappear. It should have a name in the format COMx
where x
is a number. If you installed npm in Windows, you will run the ground station software with the command npm start COMx
. If you install npm in WSL, you will run the ground station software with the command npm start /dev/ttySx
where x
is the same number as in Device Manager.
Make sure you have logs
folder in that directory or else this will fail!
Open up a web browser and go to http://localhost:8080. If opening this gives you a blank page, inspect element
. If the error says something along the lines of cannot find dist/openmct
then...we really don't know. For now, contact someone who has it working to email you their openmct
package. Then from ground_station_openmct/node_modules
run rm -rf openmct
then unzip the emailed openmct package into ground_station_openmct/node_modules
.
Spacecraft Structures involves designing an engine mount analogue that is tested using a lever and a dummy weight shaped like a rocket to mimic the forces of a rocket launch. The objective is to design and build a structure that can withstand 3 launches using minimal materials. The entire workshop takes around 2 hours and has been run at Splash, Expanding Your Horizons, and SWE High School Engineering Program.
The structure itself is composed of two 1/4" plywood plates with enough space in between to fit a film canister, which represents the rocket engine. Coffee stir sticks and hot glue are the only other materials provided to construct the rest of the structure.
The structures are tested by placing them in between the rocket and the lever and dropping a 15 lb (6.8 kg) weight on the other side of the lever from shoulder height.
Current slide deck: https://docs.google.com/presentation/d/1Tvh4uL7LV4K578TAZ41O1hmjDH1xtWBw7VfJ3QOH_RE/edit?usp=sharing
Short version slide deck: https://docs.google.com/presentation/d/1qYkuULqG4q63alXvwlvJgF1JBPIipl0p_xpdBJXMaAc/edit?usp=sharing
Vector file for laser-cutting top and bottom plywood plates: https://drive.google.com/file/d/1LmVELYuEPEu2I09916-3BJlAm2x18kNZ/view?usp=sharing
How to solder/populate a PCB
Please note that there should be a through-hole and surface mount soldering workshop roughly every semester; ask on Discord for a date and time. It is highly recommended that you attend this workshop, as this page is more of a supplement than a stand-alone tutorial.
Now that you have a PCB, you are ready to solder. Make sure you have the following supplies:
Soldering iron
Solder
The board that needs soldering
Components to solder onto the board
Flux (either liquid in syringe or pen form)
Tweezers (for surface mount soldering)
Solder wick (not necessary, but useful)
Solder sucker (not necessary, but useful)
When putting together your board, remember to test as you solder. This will make sure that you have a better idea of where a bug is if you run into one. This means soldering on a module and then testing that module before moving on to soldering another module. Refer to "Using Lab Equipment" on information relevant to testing. An example of how to break up soldering a board into modules is as follows:
Voltage regulator/power input. Test with a multimeter (and by power LED).
Microcontroller. Test by writing a simple program to verify that you can use digital input/output pins. Can also verify by flashing a program that uses the debug UART port.
Sensors/actuators (one component at a time). Verify the component works by interfacing with the microcontroller. This may require having some code ready to communicate over I2C or SPI!
Remember to put away all tools you used when you are done. Keep whichever space you are working in clean.
Through-hole soldering steps (repeat these steps for each joint):
Place your circuit element into the PCB.
Melt a small blob of solder on the tip of the soldering iron. This is called “tinning the tip” and it improves the transfer of heat from your soldering iron to the component you want to solder. Make sure to do this to avoid oxidation and permanently ruining the tip.
If necessary, apply flux to the metal ring on your PCB. Flux is usually more important for surface mount soldering.
Touch the tip of your soldering iron to the metal ring and component leg (of a through-hole component) at the same time. (See diagram below)
Feed solder into the joint (not the soldering iron) while this is happening. It should only take a couple of seconds at most to fill the joint with a proper amount of solder.
After enough melted solder is present, stop feeding solder and remove the tip from the joint.
Clean the tip of the soldering iron by dabbing the tip on a wet sponge.
Let the joint cool down for at least 5 seconds and then trim the ends of the wire(s).
The following tutorial is for through-hole soldering:
Surface mount soldering is a bit more difficult. The components are small, and it's easy to short pads (the metal parts that you're soldering onto) and components together. But all it takes is practice!
The steps to do surface mount soldering is similar to through-hole:
Place your circuit element onto the PCB.
Tin the tip. Very important.
This is when it's good practice to use flux! Apply some to the pad before soldering. After you're done, put some flux on the solder blob and apply heat with the soldering iron to flatten peaks.
While soldering, touch the tip of your soldering iron to the metal pad and edge of the component leg at the same time.
Feed solder onto the pad (not the soldering iron) while this is happening. It should only take a couple of seconds at most to cover the component and pad with the right amount of solder.
After enough melted solder is present, stop feeding solder and remove the tip from the pad.
Clean the tip of the soldering iron by dabbing the tip on a wet sponge or brass sponge.
Let the joint cool down for at least 5 seconds and then refer to the flux step above.
The following tutorial is for surface mount soldering:
There are many free through-hole components around Supernode, and you can just ask someone for surface mount components. It's important that you practice. Please ask for help if necessary.
A walkthrough of our component selection process for designing boards.
One of the challenges of circuit design is narrowing down exactly which components you want to use. For example, suppose you need to include a zener diode as part of your circut. A quick internet search on supplier websites reveals more than 70,000 possible options! How are you supposed to narrow it down?
This option is relatively simple but works very well: browse through some of our old electronics projects and re-use components that we've used before. For example, if you need a zener diode, check our past projects to see if any of them incorporated a zener diode, and re-use that specific diode for your current project (as long as that diode meets your current project requirements). Some of the projects that you can browse are:
Open up kicad and browse through their schematic symbol libraries. In these "Kicad default libraries" you can find a whole host of specific part numbers for each general type of component (amplifiers, transistors, etc). There are two main advantages to using components from the Kicad default libraries: first, obviously, you'll have easy access to the symbol and footprint for your part, without having to make them yourself or search online. Second, by virtue of the component being included in Kicad's deafult libraries, you'll know that it's a very popular component.
If we go back to our old example of trying to find a zener diode, here's how we can search the Kicad default libraries. First, open up the schematic editor and select the button to add a component:
Then, type "zener diode" in the search bar:
Most of the options it shows us here at the top are 'generic symbols' and aren't specific part numbers.
If we scroll down, now we can see some specific part numbers. For example, here I've selected the BZV55B2V4 zener diode, and if we later decide we want to use it in our project, we can buy that specific diode from digikey.
Sometimes, if a component isn't available in the Kicad default libraries, you can find it in an online Kicad library, which you can download and incorporate into your project just like a component from a default library. One of the best resources for finding these online kicad libraries is snapeda.com. This website allows your to search by part type (or by specific part number) to get symbols and footprints that you can integrate into your kicad project.
If you go to the main page and type "zener diode" then the search results will look something like this:
One of the great things about SnapEDA is that it tells you how popular each part is by displaying the number of times that each symbol and footprint has been downloaded. If something has over 100 downloads, that usually means its a very solid choice. For this reason, looking up parts on SnapEDA is still useful even if you already have the symbols and footprints. If you're trying to choose between two zener diodes, and one of them has much more downloads on SnapEDA than the other, then that might help to inform your choice between them.
Digikey.com is the main website that we use to search for and purchase parts. However, we frequently buy parts from other sources as well--mouser.com is a good example, offering almost all of the same features as digikey. We also buy parts from Amazon sometimes, like the ESP32s used in the LE2 ground system.
For now, though, you can stick to digikey, as that will make things simpler. Continuing with our zener diode example, you can start by typing 'zener diode' into the search bar at the top of the screen. Doing so will lead you to a page that looks like this, where you can select the category of components to browse:
Click on "Diodes - Zener - Single." Next, you'll see a page that looks like this, where you can browse all the specific components to purchase:
You can start narrowing things down by selecting some filters. Under "product status", select "active"--this is one filter that you can always select right off the bat. After that, scroll through the rest of the filters and select the ones that apply to your project. For example, maybe you know that you'll need a zener voltage of 12V exactly--in that case, you can go to the "Voltage - Zener (Nom)" filter and select 12. Additionally, maybe the project requirements stipulate that the zener diode needs to support 500 mW of power; in that case, you can go to the "Power - Max" filter and select every power level above 500 mW. Oftentimes, you can also go to the "Mounting Type" filter and select "surface mount" because we usually use surface-mount components on PCBs due to their small size. (Though sometimes we do need to use through-hole components, usually when the components have some kind of high-voltage or high-current function).
Press the red "apply all" button after selecting your filters. This drops the number of results down to about 617. Next, unless you have a specific part number in mind, go to the "Quantity Available" tab and press the down arrow button to sort in descenging order or quantity available. This is done for two reasons; first, the parts with a very high number available are generally the most popular, and therefore the best to use. Second, we have had some problems in the past with parts that are out of stock on digikey (for example: we designed CAS in 2020 and included a component called the BNO055. That component ended up going out of stock, and as of 2023, it's still out of stock. Depending on how far in the future you're reading this, it may still be out of stock today!).
From here, you can scroll down the list of most popular components and note down any that look appealing. Note that, when digikey reports the quantity of a component, they include both the quantity that they have "in stock" (the normal way to buy them) as well as the quantity available on the "marketplace." The marketplace is relatively new so STAR doesn't have much experience buying from there. If you find a component you really like that's only available on the marketplace, by all means go ahead and buy it, but if you want to stay on the safe side, then stick to the components that are listed as "in stock" on digikey. At this point, you'll probably be able to get a shortlist of several components (10 or so) and start deciding between them.
Look at options from a reliable vendor. Some vendors that make lots of good components include Texas Instruments, Onsemi, Diodes Incorporated, Analog Devices, and NXP. Note that digikey allows you to filter by vendor when you are doing the filtering step.
If you are deciding between a few components, read their datasheets. Some datasheets have detailed pinouts, application circuits, debugging information, and more, whereas some other datasheets only have the absolute bare minimum. Components with more comprehensive datasheets are generally a better choice because they'll be easy to use.
Solderability is very important! Components with "little legs" (there's an official package name but I can't remember it) are much preferred because the metal part sticking out makes it relatively easy to solder. In contrast, some components have all their pads directly under the package without any legs at all. This makes it much more difficult to solder, although it can still be done by STAR's capabilities if there are no other options.
Go to adafruit.com if you're interested in getting breakout boards specifically. Adafruit has a much narrower scope than most other component distributors, and they tend to specialize in things that you can connect to an arduino or esp32, such as sensors and actuators. Adafruit usually has very extensive documentation and tutorials for using their components, which makes them a really appealing choice.
Some components are used a lot by STAR simply because our club used them before many times, so they should be prioritized when doing components searches. Some examples of this include the STM32F401RE microcontrollers, which was used in many projects (most notably CAS), as well as the ESP32 devkit-C V4, which was used for ELLIE and LE2 electronics.
If there's one component that is mostly really good but won't work for some reason (maybe its out of stock, or it doesn't meet the required power rating, or something else), try looking for a closely related component. Most manufacturers use a sort of naming convention in which components have more similar part numbers if they are more closely related. Many datasheets will even have an "ordering information" section near the end where they tell you the exact meaning of the naming convention for that family of components.
If the component you're looking for is something that a microcontroller communicates with, you should prioritize components that already have drivers written for them (available online), so you don't have to write drivers yourself.
You can literally just google something like "best zener diode" and see what the top few results are. This isn't the most effective strategy, but sometimes it can work.
You can click on each individual part to see more details about its symbol and footprint. Note that not all components will have both a symbol and footprint provided--some have only a symbol, some have only a footprint, and some have neither. Components with the will have a symbol, and components with the will have a footprint. If you get a component with only a symbol, it is possible to make the footprint yourself and incorporate both into your project (and vice versa). However, note that symbols are generally much easier to make yourself than footprints.