Thrust stand for pulsed plasma thrusters

Abstract

A torsional-type thrust stand has been designed and built to test pulsed plasma thrusters in both single shot and repetitive operating modes. Using this stand, momentum per pulse is determined strictly as a function of thrust stand deflection, spring stiffness, and natural frequency. No empirical corrections are required. The accuracy of the method was verified using a swinging impact pendulum. Momentum transfer data between the thrust stand and the pendulum were consistent to within 1%. Following initial calibrations, the stand was used to test a Lincoln experimental satellite (LES-8/9) thruster. The LES-8/9 system had a mass of approximately 7.5 kg, with a nominal thrust to weight ratio of 8.0×10−6. A total of 34 single shot thruster pulses was individually measured. The average impulse bit per pulse was 266 μN s, which was slightly less than the value of 300 μN s published in previous reports on this device. Repetitive pulse measurements were performed similar to ordinary steady-state thrust measurements. The thruster was operated for 30 min at a repetition rate of 132 pulses/min and yielded an average thrust of 573 μN. Using average thrust, the average impulse bit per pulse was estimated to be 260 μN s, which was in agreement with the single shot data. Zero drift during the repetitive pulse test was found to be approximately 1% of the measured thrust.