Development of Test Methodologies and Setups for Thrust Measurements of Cold Gas Micro-thrusters for CubeSats

Abstract: Measuring the thrust of cold gas micro-thrusters, due to the small magnitude of the generated force, is a challenging task, and to obtain satisfying quality of results usually careful adjustments of the setup has to be performed. The work presented in this paper aims at improving the quality of such measurements at the GomSpace Sweden company. The work consists of two parts: In the first part the author focuses on improving current thrust measurements setup implemented in the company, which consists of a vacuum compatible laboratory scale. It was observed that the results obtained from this setup were approximately 25‒35% lower than expected. A test campaign performed within the work found that this was associated mainly with backflow of plume expansion gases. Covering the scale and the tested propulsion unit with a box having openings only for thrusters was proved to be sufficient setup upgrade to mitigate the issue. In the second part of the project an alternative setup utilising a hanging pendulum-based solution with strain measurement-based force sensor is proposed and its design is thoroughly described. Results of initial tests of a 3D printed prototype of this setup are presented, proving its potential to produce results with better quality of output than the laboratory scale.