Fully kinetic modeling of a divergent cusped-field thruster

Abstract

A fully kinetic, particle-in-cell plasma simulation tool has been incrementally developed by members of the Massachusetts Institute of Technology Space Propulsion Laboratory. Adapting this model to simulate the performance and plasma dynamics of a divergent cusped-field thruster is discussed. Strong magnetic fields in the cusps (B0.5 T) necessitate using a time step on the order of a picosecond in order to resolve electron cyclotron trajectories. As a result, successfully completing a divergent cusped-field thruster simulation with the full magnetic field strength has yet to be accomplished. As an intermediate step, simulation results of a divergent cusped-field thruster with the magnetic field at 1/5 the actual value are presented, including performance parameters and internal plasma structure details. Evidence suggests that even at 1/5 the magnetic field strength, ions are fully magnetized within certain regions of the divergent cusped-field thruster. This has strong implications concerning the basic operating principles of the thruster because the Hall effect does not result in a net flow of current in regions where ions are fully magnetized. Further modifications that may lead to successful simulations of divergent cusped-field thrusters at full magnetic field strength are also outlined, which may allow for more detailed studies of the plasma structure and performance of the cusped-field thruster.