Enhanced propulsion performances under optimum parameters in closed drift accelerators

Abstract

Parametric estimations of propulsion performances were conducted through numerical analysis and experiment in closed drift accelerators, the so-called hall thrusters. At high-voltage mode of DC regime which is ordinary operation region, the large-amplitude discharge current oscillation in the tens of kHz has been a serious problem that should be solved with a view to improving the stability of operation and the durability of thruster-in-itself. So the dependencies of propulsion performances, (thrust, specific impulse and thrust efficiency) including both amplitude and frequency of “low-frequency oscillation” on various parameters, (discharge voltage, neutral species temperature and magnetic field configuration) were investigated in the present study. Besides the following possibility was suggested: The operational conditions or the design providing the larger “average length of ionization-zone”, which we introduced as a new physical parameter, made it possible to operate with suppressing amplitude. In addition, the mechanisms of controlling amplitude were clarified from the spatio-temporal variations of plasma properties and electromagnetic field in the acceleration channel for single-cycle of discharge current oscillation. The knowledge obtained here would be useful for proposing ideal operation and design of hall thruster as a promising high-performance propulsion device in space missions requiring for high-reliance.