Improved Design and Characterization of MicroNewton Torsional Balance Thrust Stand

摘要

Torsional balance thrust stands are in common use for performance measurement of small thrusters in the microNewton to milliNewton thrust ranges. Due to their mechanical nature these stands must be calibrated regularly to minimize drift caused by external factors such as ambient temperature change and internal variations such as inertial differences in test articles. Common calibration methods include electrostatics, linear induction motors, and piezoelectric impulse comparison, all of which in turn must be initially calibrated for force. The thrust stand in the High Vacuum Lab at Purdue University utilizes an electrostatic fin assembly originally calibrated with repeatability errors less than 3% at forces over 50 μN. The need for more accurate measurements, in particular, for a MEMS microthruster array characterization and sensing of Knudsen thermal force at low pressures, prompted a campaign of recalibration and reconfiguration to achieve better performance to values less than 10 μN. The main goals of this paper are to present the improved design of the microNewton thrust stand and characterize its performance for measurement of Knudsen thermal force and thrust performance of a microfabricated thruster array.