Flight computer

This repository contains the schematics and firmware for the Martlet IV Avionics system - Project Strix.

Project Strix is a single-board flight computer designed to carry out essential tasks during the launch of Martlet IV. Powered by an ARM Cortex-M4, Strix is able to perform a plethora of functions in real time, and respond to dynamic events as they happen.

Specification

The system must be able to

1. Carry out data acquisition for the Pulsar engine sensors.
2. Perform altimetry for the rocket for the purpose of:
   1. Finding the maximum altitude obtained by the rocket.
   2. Deploying the parachutes^*.
3. Store the data obtained from 1. and 2. using a storage device in a protective container.
4. Transmit the data obtained from 1. and 2. to a ground station in real-time for the purpose of:
   1. Informing the ground support team of the Pulsar engine sensor data before launch (i.e. during filling operations).
   2. To aid an investigation should the rocket vehicle suffer an in-flight malfunction.
   3. To find out the rocket's maximum altitude in case loss of the rocket prevents retrieval of stored data.

^*Note that a commercial off-the-shelf 'Stratologger' altimeter will also be wired to the parachutes and will also be able to deploy them for redundancy.

Core Modules

The system is composed of several sub-modules, all connected to the central microcontroller for unified control.

Altimeter

The onboard altimeter uses two redundant IMUs and barometric pressure sensors to accurately determine the altitude of the rocket.

Sensor Front-Ends

The sensor front-ends take data from the Pulsar engine sensors and converts them into voltages readable by the microcontroller's onboard ADCs. The subsystem supports the following sensors:

Radio

The radio subsystem handles the onboard two-way ISM-band radio, which allows Strix to both send telemetry to ground control and receive telecommands. A modular architecture allows for precice control of output power to ensure the rocket operates within local limits. The subsystem also contains a GPS receiver, which assists in location of the rocket after landing.

PSU

The modular power supply provides regulated 1.8V, 3.3V, and 12V power to the flight computer and blackbox. Power is delivered from 2x 18650 Li-ion cells, which can be recharged on the pad before switching to internal power.

Design Constraints

The space allowed for the system is shown below (dimensions in mm):

The module must also not take up the entire space; some area or a hole must be left empty to allow other cables to pass through the rocket (in addition to the central hole).

The module, including any batteries and mounting hardware, should have as little mass as possible - it must weigh no more than 500g.