Performance evaluation of a low power Hall thruster with carbon dioxide propellant

Abstract

Carbon dioxide (CO2) is an attractive candidate for condensable propellants because its availability and storability. Although several studies have been reported on adopting CO2 as a propellant for Hall thrusters, there have been few studies on CO2 standalone operation, and none of them have focused on physical phenomena in plasmas. This study experimentally evaluated, thrust performance and plume characteristics of a 100 W-class Hall thruster under CO2 operation. CO2 operation was compared to xenon operation under the same discharge power conditions to determine its unique properties. As typical thrust performance under this experimental condition, a specific impulse of 727 s, thrust-power-ratio of 19.8 mN/kW, and anode efficiency of 0.0711 were achieved at a discharge voltage of 200 V and a discharge power of 352 W under a background pressure of 3.4 × 10−2 Pa. Plume measurements showed that mass utilization efficiency was 0.228 under CO2 operation, which was particularly poor compared to under xenon operation. The first reason for this is that the ionization mean free path of CO2 is 5.18 mm, about eight times longer than that of xenon. The second reason is that the energy is used for other processes, such as dissociative ionization and dissociation etc., considering the reaction process of the particles. Therefore, the results suggest narrowing the channel width to increase the channel density, and increasing the magnetic field strength to suppress the discharge current as ways to improve thrust efficiency.