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, tempĀerature, 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 ā no need for multiple batteries.
Precision sensor & 24 bit ADC yield superb 0.1% accuracy.
Built-in voltmeter reports battery voltage on powerup ā no more guessing about battery condition.
Post flight locator siren aids in locating your rocket.
Confusion-free individual terminal blocks ā 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 āsecond chancesā 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
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
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 subteamās 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.
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: 1/8ā (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 3/16ā 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: 8ā
Tip Chord: 3ā
Height: 5.5ā
Stability: 1.27 cal
Lower Stage
Root Chord: 10ā
Tip Chord: 3.5ā
Height: 5.7ā
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).
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.