Jet Propulsion Laboratory Small Satellite Dynamics Testbed Planar Air-Bearing Propulsion System Characterization

Abstract

The Small Satellite Dynamics Testbed (SSDT) at the Jet Propulsion Laboratory offers infrastructure that supports small satellite guidance and control testing in a relevant dynamics environment while constrained by the gravity of Earth. One of the testing environments of the SSDT is its planar air-bearing platform, which has two lateral and one rotational degrees of freedom. This paper details the new position-control system and its compressed-gas thrusters of the planar air-bearing test platform, and characterizes the pertinent parameters related to the platform and propulsion system. A detailed description of the hardware and software systems of the platform is provided. Testing shows a maximum float time of 13.5 min, an average maximum thrust per thruster of 0.51 N, a tank pressure drop of 6.85 psi/s, and minimum impulse bit of 40 ms. The paper further presents results necessary for designing position controllers for use on this system, such as the relationship between number of thruster firing and output force, and the timing latency in the thruster firing control system. The paper shows that the embedded computer used in this platform exhibits timing delays of approximately 34 ms. Implications of these results on control system design are discussed in the conclusions.