This document details the rough list of changes made to the original SRAD Sporadic Impulse rocket in order to have a COTS test launch be done with it.
New General Objectives:
- Preserve as much of original airframe/geometry of original SRAD SI.
- Reach an apogee of +1.5km - For testing of recovery systems and electronics. ~3km would be extremely difficult, cannot adequately replace impulse of SRAD engine.
- Attempt to simulate properties of Sporadic Impulse as closely as possible for testing purposes
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Use COTS Sporadic Impulse to test recovery systems and electronics of rocket
- To test recovery system - Must go to around above 1.3km
NOTE : RICARDO AND Eggtimer are present for redundancy purposes.
Constraints:
- Minimal off-rail launch velocity of 30m/s.
- Maximum touchdown velocity of 5m/s for recovery.
- Weight at recovery deployment must be similar to SRAD conditions.
Potential Issues:
- Sourcing a COTS motor with total impulse comparable to that of the SRAD hybrid engine.
- What are we doing with the tank? Probably run it either entirely dry or entirely full throughout.
- Rocket reaches speeds of Mach 0.6 at launch. May encounter stability issues b/c static margin calculations become a bit weird there.
General Plan:
- Use 2 K660 Cesaroni motors as boosters, procured from Rockets and Things.
- Use 2 K570 Cesaroni motors as inner engines, procured from Rockets and Things.
- Fiddle with fin design to recalibrate stability of the rocket.
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Fill fuel tank with water as ballast in order to match weight of COTS Sporadic Impulse to the weight of Sporadic Impulse with its fuel tank empty.
- This is in order to provide recovery as similar testing conditions as possible
- Maximum acceleration of 87.2 m/2^2
17/10/2020 Update:
- Made different configurations for wet, dry and no water rockets. Wet still has a 4 motor config while the other two have a 3 motor config.
- Wet mass config requires 12.6 Kg (not possible with tank volume we have, it'll go to a max of 11.6) of water whereas dry config needs 5.64 to match the dry mass of SI which will be 29.2 Kg.
- Can't use the tank as it will be rewelded at that time. Along with this, using water will not be an option.
- Use 1 K660 and 2 K570 as inner engine & boosters respectively because of reduced mass. This still might be overkill considering the fact that we don't have a tank now so we need to review .
- 3-D print a smaller section (around 30 cm) and then add ballast to match the dry mass of rocket to test recovery system but needs to be reviewed .
24/10/2020 Update
- Removed fill & feed system from config - No tank and engine, so what for.
- Removed fore transition - no tank, so no need for transition and can instead use one flush body tube.
- NOTE: above changes made b/c Eddie confirmed we most likely can't use tank.