Evaluating argon and xenon ion thruster propellants and their interaction with atmospheric species at 360 km altitude

Motivated by recent developments in the commercial sector related to the use of argon as a spacecraft propellant, this paper presents the first comparison between two ion thrusters using xenon and argon as propellants. We use numerical simulations to model a satellite at 360 km altitude, a typical Low-Earth Orbit, and so therefore include ambient gases as well as the propellant in our modelling. We use a hybrid particle-in-cell scheme in which the particle density determines whether interactions are simulated using a Monte Carlo collision or using a direct simulation Monte Carlo collision model. Plume shape, overall propulsive performance and interactions between the ionized propellant, ambient species and the satellite’s surface are considered here. Our calculations indicate that argon produces a 67.1% higher specific impulse than xenon. The key benefit of argon over xenon is that it produces a plume with a lower particle number-density and correspondingly a smaller back-flow of ionised propellant that may form a plasma sheath around the spacecraft and disrupt radio-frequency communications. This appealing property implies that argon may be more suitable than xenon for long missions.