Rocket Development¶
Last updated: 2026-04-10
Last updated: 2026-04-11
Focus: avionics, flight software, and the systems engineering side — not propulsion chemistry.
Recent Finds¶
SparkyVT HPR Rocket Flight Computer: 1600 sps, Mach 2.3, 250+ Flights (GitHub)¶
The most mature open-source HPR flight computer project: Teensy 4.1-based (ARM Cortex-M7 @ 600 MHz), runs at 1600 samples/second for all sensor channels simultaneously. Features: 4 programmable pyro outputs, Mach-immune apogee detection (barometer-only apogee detection has false positives during transonic phase — this system suppresses them), air-start and two-stage support, tilt-sensing safety inhibit (won't fire pyros if rocket is off-axis post-apogee). Flight-tested on 250+ flights including M and N class motors, reaching 34,000 ft AGL at Mach 2.3. The PCB fits in a 38mm tube coupler. Practical for high-power club rocketry through experimental class. Sensor fusion architecture: complementary filter for altitude (IMU + barometer), GPS for position logging post-flight (not used real-time for apogee detection).
Georgia Tech GTXR Two-Stage Sounding Rocket: EKF for GNSS Lockout (AIAA 2024)¶
University-level sounding rocket avionics design using Extended Kalman Filter (EKF) for state estimation — specifically addressing GNSS lockout (GPS drops under high-G and supersonic flight). Modular avionics: separate boards for power, compute, and RF with a CAN bus backbone. EKF fuses 6-DOF IMU + barometer during GPS blackout intervals. Key lesson: GPS alone is insufficient above Mach 0.8 — the EKF must be tuned to handle the transonic barometer pressure anomaly near Mach 1.
LeLaR: DRL Attitude Control Demonstrated In Orbit — Implications for Rocket Avionics (arXiv 2512.19576)¶
While primarily a satellite ADCS result, LeLaR's Sim2Real success has direct implications for advanced rocket avionics: a deep reinforcement learning controller trained purely in simulation controlled InnoCube's reaction wheels in orbit on Oct 30, 2025 — without any in-flight fine-tuning. The training randomized over inertia uncertainty, actuator noise, and disturbances. For rocket avionics, this opens the door to DRL-based attitude controllers for TVC (thrust vector control) or active fin stabilization systems — domains where hand-tuning EKF + PID stacks for each new vehicle configuration is expensive. Key open question: can Sim2Real transfer survive the far more violent dynamics of boost phase (>5G, vibrational noise, propellant slosh) compared to the relatively benign orbital environment?
Rocket Anatomy (Systems View)¶
┌─────────────────────────────┐
│ Payload / Nosecone │ ← satellite, experiment, recovery bay
├─────────────────────────────┤
│ Avionics Bay │ ← FC, IMU, GPS, barometer, RF, power
├─────────────────────────────┤
│ Propellant Tanks │ ← liquid: oxidizer + fuel / solid: grain
├─────────────────────────────┤
│ Engine / Motor │ ← thrust generation
└─────────────────────────────┘
Avionics¶
The brain of the rocket. Handles state estimation, event detection, and recovery.
Flight Computer (FC)¶
Responsibilities: 1. State estimation — fuse IMU + GPS + barometer → position, velocity, altitude, orientation 2. Event detection — apogee, burnout, staging (for multi-stage) 3. Recovery sequencing — deploy drogue (fast) then main parachute (slow) at right altitudes 4. Telemetry — broadcast data to GCS in real-time 5. Abort / safe mode — inhibit pyrotechnics if criteria not met
Sensors¶
| Sensor | Purpose | Typical part |
|---|---|---|
| IMU (6/9-DOF) | Accel + gyro (+ mag) | ICM-42688-P, BMI088 |
| Barometer | Altitude (pressure) | MS5611, BMP390 |
| GPS | Position + velocity | u-blox M10, ZED-F9P (RTK) |
| Pyro continuity | Check e-match integrity | Simple ADC measurement |
Sensor fusion: Extended Kalman Filter (EKF) or Complementary Filter. GPS alone is too slow (1–10 Hz) and drops under high acceleration. IMU alone drifts. Fusion gives best-of-both.
Open Source Flight Computers¶
| Project | Language | Notes |
|---|---|---|
| OpenRocket | Java | Simulation only — not a flight computer |
| AltOS / TeleMetrum | C | Altus Metrum — mature, used widely in amateur rocketry |
| RAVEN | C | Featherweight Rocketry — certified recovery FC |
| Odyssey | C++ | University rocketry standard |
| Custom STM32/RP2040 | C/C++ | DIY, educational projects |
Recovery System¶
Dual-deploy is standard for high-power rocketry: 1. Drogue — small chute at apogee. Slows from terminal velocity but still fast. 2. Main — large chute at lower altitude (~150–300m AGL). Slow landing.
Triggered by barometer detecting pressure increase (descent detected) + altitude threshold.
Ejection charges (black powder) or CO2 systems physically separate sections and deploy chutes.
Redundancy: two independent flight computers, each with independent e-match channels.
Flight Software¶
State Machine¶
Each state transition has criteria: - ARMED→BOOST: accelerometer > 3g for > 0.1s - BOOST→COAST: accelerometer < 0g (burnout) - COAST→APOGEE: vertical velocity crosses zero (from IMU/baro fusion) - APOGEE→DROGUE: fire pyro channel 1 - DROGUE→MAIN: barometer altitude < threshold AGL - MAIN→LANDED: velocity < 1 m/s for > 5s
Safety Inhibits¶
Pyrotechnic systems should never fire unless ALL conditions met:
def can_fire_drogue():
return (
state == APOGEE and
altitude > MIN_SAFE_ALTITUDE and # not on pad
time_since_launch > MIN_FLIGHT_TIME and
continuity_drogue_ok and
armed_by_operator
)
Telemetry Protocols for Rocketry¶
- LoRa (433/915 MHz) — long range, low data rate, line-of-sight 20–30 km
- APRS (144.390 MHz, US) — AX.25 packet radio, nationwide receiver network
- 2.4 GHz custom — higher bandwidth, shorter range
- Iridium SBD — satellite telemetry, works anywhere (GPS + position beacon)
Typical telemetry packet: timestamp, altitude, velocity, GPS lat/lon, temperature, voltage, state.
Launch Systems & Infrastructure¶
Categories¶
| Class | Altitude | Mass | Examples |
|---|---|---|---|
| Model | <500m | <125g motor | Estes |
| High Power (HPR) | 1–30 km | H–O motors | NAR/Tripoli certified |
| Experimental | 30–100 km | Research motors | UKRA, university programs |
| Sounding Rocket | 100–1500 km | Professional | NASA Black Brant, VSB-30 |
| Orbital | 200+ km | Tons | SpaceX, RocketLab, ISRO |
Range Safety¶
For any experimental/university launch: - Flight termination system (FTS) — ground command to destroy or neutralize vehicle - Range clearance — coordinate with local aviation authority (NOTAM) - Exclusion zone — keep personnel at safe distance (debris trajectory calculation) - Telemetry — real-time position for safety officer to authorize flight termination
PropulsionTypes (Software Perspective)¶
| Type | Controllability | Restart | Notes |
|---|---|---|---|
| Solid | None once ignited | No | Simple, reliable, most amateur rockets |
| Cold gas | Throttleable | Yes | N₂ or CO₂, low Isp, used for RCS |
| Liquid bipropellant | Throttleable | Yes | Complex, high Isp, SpaceX/RocketLab |
| Hybrid | Partially | Limited | Solid fuel + liquid oxidizer (LOX/N₂O) |
For software: liquid engines expose the most control surface — injector valves, turbopumps, gimbal actuators, all with feedback loops.
Key Organizations & Programs¶
- NASA Student Launch — annual competition, HPR, universities worldwide
- Spaceport America Cup — largest intercollegiate rocketry competition
- IREC / SAC — 10k and 30k ft APOGEE challenge
- LAPAN/BRIN (Indonesia) — national rocketry research (RX series sounding rockets)
- Reaction Engines — SABRE engine (air-breathing/rocket hybrid)
- RocketLab — Electron (small orbital launch vehicle), open-source mindset, Neutron upcoming
Open Questions¶
- What's the state of propellant-free propulsion (electrodynamic tether, solar sail) for orbit raising in small sats?
- Can RP2040/STM32H7 handle real-time EKF at 1 kHz on a flight computer without RTOS?
- How does SpaceX Starship's full-flow staged combustion affect the propulsion design space for new entrants?
- What's the regulatory path for experimental rocketry launch in Indonesia (BRIN coordination)?