Linear 1-D analysis of oscillation instabilities in stationary plasma thrusters

Abstract

A one-dimensional, linear perturbation model was formulated to aid in the analysis of the low-frequency (33 kHz), axial oscillation instabilities observed during the operation of Stationary Plasma Thrusters. The first six solutions of this l st order perturbation model were determined by scanning the complex frequency plane and were addressed in this study. Of these modes, two notable patterns of behavior were found and discussed. The first group of modes had waves which translated through the thruster, with a fundamental harmonic of 49.7 kHz. The second group, having a fundamental harmonic of 74.2 kHz, exhibited a sloshing type of behavior and was found to have several characteristics of a predator-prey type cycle. Although all modes were found to be highly damped, contrary to the existence of oscillation instabilities, it is believed that an ionization-acoustic resonance instability could be excited.