We’ve released the design and code for the Gideon Mk1 flight computer with data logging capability as open source. Code is available on GitHub and the hardware can be built by anyone who can solder Adafruit components This design involves $57 of parts and can log relative altitude (by barometric pressure), temperature, and all G-forces and orientation during the flight to a durable SD card as a CSV file.
We also have a design for a 55mm payload fairing nosecone that can carry these electronics on board a 55mm rocket tube. You will be able to buy the nosecone design files or fully printed nosecones at our new sister website, AsteriaFab, a 3D printing/fabrication business.
Here’s some pictures of GideonMk1 being assembled, tested and flown on our Lyrid and Rhea rockets.