Computational modeling of expanded plasma plumes in vacuum and in a tank

Abstract

Electric propulsion devices have shown to offer substantial fuel savings for various space missions. Hall thrusters, specifically, have shown great promise over the years due to their near optimum specific impulse for a number of space missions. The Hall thruster, however, releases a partially ionized plasma plume which contaminates any surface it comes into contact with. Backflow contamination can lead to sputtering and effluent deposition on critical spacecraft components. A computational method for studying these interactions was developed by David Oh in 1997. He developed a Particle-in-Cell and Direct Simulation Monte Carlo (PIC-DSMC) algorithm to model the expansion of a plasma plume from a Hall thruster into a vacuum. In his work he implemented a plasma-surface interaction model which determined erosion rates on surfaces made of quartz, silicon and silver but he did not track the surface material removed. In this work Oh's model is expanded to include the removal and tracking of material from generic spacecraft surfaces and the walls of a vacuum tank. Sputtering yields adopted in this model are based on sputtering theory developed by Matsunami and Yamamura. Since the plasma can have a negative impact on spacecraft subcomponents, a method for protecting the spacecraft (in the form of a protective shield) is proposed, studied, and recommendations are discussed.