I have been interested in model rocketry for a long time. Putting the time and energy into designing and building a model rocket, watching it leave the launch pad in a plume of smoke, and fly into the sky is very exciting and rewarding. The model rocketry community is a very passionate and supportive group, too. I have wanted to dive into the world of model rocketry for a long time and have finally decided to pursue it. In this post, I’d like to introduce my ideas for designing and building a model rocket flight data computer.

MicWro Engineering is developing a model rocket Flight Data Unit (FDU) to log in-flight performance data and give further insight into a rocket’s flight.

Functional Requirements

• The FDU shall include a signal channel to deploy a parachute at apogee.
• The FDU shall include a buzzer to aid in locating the rocket during recovery.
• The FDU shall fit within a 4 inch diameter rocket body.
• The FDU shall log data at a minimum sample rate of 50 samples per second.
• The FDU shall write flight data logs to a flash memory chip and dump the logs to a Micro SD card at the end of flight.

Sensor Requirements

• The FDU shall, at minimum, measure and log the following parameters:
  • Position
  • Speed
  • Acceleration
  • Orientation
  • Apogee (maximum) altitude
  • Atmospheric temperature
• The FDU shall include the following sensors:
  • IMU (accelerometer + gyroscope)
  • Compass
  • GPS
  • Barometer
  • Temperature sensor

Accelerometer Requirements

• The accelerometer shall have a measurement range of at least +/- 50G’s.
• The accelerometer shall have a sample rate of at least 100Hz.
• The accelerometer shall have an ADC resolution of at least 12 bits.
• The accelerometer shall communicate using a SPI interface.

Gyro Requirements

• The gyro shall have a measurement range of at least +/- 500 degrees per second.
• The gyro shall have a sample rate of at least 100Hz.
• The gyro shall have an ADC resolution of at least 12 bits.
• The gyro shall communicate using a SPI interface.

Compass (Magnetometer) Requirements

• The compass shall be capable of measuring earth’s magnetic field.
• The compass shall have an ADC resolution of at least 12 bits.
• The compass shall have a sample rate of at least 100Hz.
• The compass shall communicate using a SPI interface.

Altimeter (Barometric Pressure Sensor) Requirements

• The altimeter shall have an ADC resolution of at least 12 bits.
• The altimeter shall be capable of measuring atmospheric pressures up to 30km altitude AGL.
• The altimeter shall communicate using a SPI interface.

GPS Requirements

• The GPS shall have a sample rate of at least 10Hz.
• The GPS shall communicate at a serial baud rate of at least 115200 bauds per second.

These are high-level requirements that will be refined as development progresses.

Design Timeline

Here is an approximate flow of events that this project will follow:

1. Define project requirements
2. Select electronics
3. Design electrical schematic
4. Design PCB
5. Design sensor fusion algorithms
6. Develop software
7. Ground testing
8. Design a rocket
9. First flight test!

Ideas for Future Iterations

These features would be nice to have and are good features for future iterations:

• Transmit telemetry data to a ground station.
• Dual deployment system.
• Engine TVC.
• Fin control.