The Illinois Space Society Guides You Through the Creation of TARS MK4, Its Latest Flight Computer

The Illinois Space Society has celebrated the completion of its fourth-generation rocketry flight computer, TARS MK4, with a guide to how and why it was designed the way it is — while also releasing the project files for others to inspect and use.

"We're a team of about 100 undergraduate engineers from the University of Illinois at Urbana Champaign, and our mission is to be one of the first collegiate teams to design, build, and launch a two stage rocket 100km to the Kármán line," the ISS team writes by way of introduction.

"TARS MK4 is our premier 4th generation flight computer designed to compete in the 2023 Spaceport America Cup. It's capable of live radio telemetry, GPS tracking, autonomous state estimation, and controlling our rocket's apogee through an air brake mechanism that creates drag to slow down and reach a specific altitude for the competition."

TARS MK4, named for the sarcastic robot assisting the heroes of the 2014 Christopher Nolan film Interstellar, is split into three boards: a telemetry board, TELEM; a flight computer, FCB; and the power management board, PMB. "This allows us to get more board space for surface mounted devices (SMD)," the team explains, "and allow for more people to simultaneously work on them with KiCAD."

The finalized design is centered around a Teensy 4.1 microcontroller, mounted as a module to the FCB, with an Espressif ESP32-S3 and Microchip ATmega328P as auxiliary microcontrollers providing telemetry and power management. As a sensor payload, TARS MK4 includes barometer, accelerometer, gyropscope, and magnetometer sensors, with data communicated back through a LoRa radio link via an Adafruit RFM96W breakout board.

"Our telemetry thread in flight software sends data to our embedded LoRa radio transceivers which then beams it down to our grand station receiver where it's parsed and then displayed onto our custom ground station software running on the Electron Framework," the team explains. "It's built as a browser based application enabling it to easily be [run] locally on a laptop or even hosted on a cloud webpage for people to view on their phones."

The Illinois Space Society's full project write-up, with tips on everything from board design to assembly, is available on Instructables; the TARS software and hardware designs are published to GitHub under an unspecified open source license.

"Hopefully in a few months time we'll be ready to reveal our next generation flight computer called MIDAS MK1," the team adds. "We're aiming to shrink all of TARS into one board and add pyrotechnic circuitry to be able to initiate in-flight events such as parachute recovery."