Development of a Torsional Thrust Balance for the Performance Evaluation of 5-N Class Thrusters

摘要

Development of high performance micropropulsion technologies will greatly benefit next-generation interceptors and microsatellite missions. Miniature interceptors (multiple kill vehicles, RPG countermeasures, etc.) and microsatellites (space-based radar formation) are constrained in mass, envelope, and electrical power. Therefore, all spacecraft subsystems, including the propulsion systems for orbital maneuvering (divert propulsion), attitude control, and station keeping, have to be miniaturized. However, accurate performance evaluation of N-class thrusters requires the development of low-thrust measurement technologies. This article presents design, development, and preliminary testing of a Torsional Thrust Balance (TTB) for performance evaluation of miniature thrusters. The thrust balance allows a measurement range between 25 mN to 4.5 N and can be configured for both steady-state and pulsing operations. Additionally, the TTB can accommodate a wide range of thruster weight by compensating the, moment arm length with a mass counterbalance system. Displacement measurements are made using a triangulated laser-positioning sensor, the output of which is converted to thrust via a LabView interface. The use of frictionless pivots, a moment arm, and counterbalanced-stand design offset the influence of measurement complications such as environmental interference, natural vibration frequencies of the system, and tare forces. In future studies conducted with this system, uniformity of the reference positioning of the thruster for each firing will be ensured with the use of a one-sided damping system used in conjunction with a limit sensor to both reposition the thruster arm and trigger the thruster firing. The accuracy and precision of the TTB was tested using a 0.5-N reference cold gas thruster. Thrust measurements were shown to be accurate and repeatable.