Effect of Pressure Level on the Performance of an Auto-Initiated Pulsed Plasma Thruster

Abstract

Pulsed plasma thrusters (PPT) are micro-propulsion devices used in satellites for station keeping. Conventionally the plasma discharge in a PPT is initiated by a spark plug. The primary objective of the present work was to develop and characterize a PPT that does not need a spark plug to initiate the plasma discharge. If the spark plug is eliminated, the size of the thrusters can be reduced and arrays of such thrusters can be manufactured using micro electro mechanical systems (MEMS) techniques, which can provide tremendous control authority over the satellite positioning. A parallel rail thruster was built and its performances were characterized inside a vacuum chamber to elucidate the effect of vacuum level on the performance. The electrical performance of the thruster was quantified by measuring the voltage output from a Rogowski coil, and the thrust produced by the developed thruster was estimated by measuring the force exerted by the plume on a light weight pendulum, whose deflection was measured using a laser displacement sensor. It was observed that the thruster can operate without a spark plug. In general, the performance parameters such as thrust, mass ablation, impulse bit, and specific impulse per discharge, would increase with the increase in pressure up to an optimum level due to the increase in discharge energy as well as the decrease in the total impedance of the plasma discharge. The thrust efficiency is found to be affected by the discharge energy.