Design, development and test of the control unit for a small cold-gas propulsion system.

The present thesis is linked to a project launched by Tyvak International concerning propulsion module development for CubeSat proximity operations. The project is born from a market analysis that had revealed a gap in the development of thrusters suited to this application, therefore Tyvak, in collaboration with T4i, started a preliminary design of a cold-gas thruster for a 6U CubeSat targeted at missions that require proximity operations. The objective of this thesis is the development and test of the control unit for this propulsion module, in particular the work is focused on the implementation of the software, the assembly of a development board and the test of the functionalities and performances of the designed system. Before starting the development of the code, an analysis was carried out to determine functions that the software should accomplish, and which interfaces the system should have. After determining this, the design of the code is divided into modules in order to more easily develop and test them. Of these, the main modules are the control and settings of interfaces, data and telemetry acquisition, and strategies to control valves and heaters. All software is developed to maintain the main loop time as fast as possible, in order to have a high time resolution in the valves control. Subsequently, a test campaign is carried out with two different kinds of tests:these are referred to as software tests, and hardware tests. The first are performed with the help of Raspberry Pi used as a GNC simulator and have the objective of individually testing the functionalities and time performances of all commands. While the hardware tests aim to test the control algorithm implemented to keep the temperature in operative range for thrusting and to assess the real valves opening times linked to hardware delay and not only to the software reactivity.