Numerical simulation of ion thruster plume to spacecraft charging

Dense plume induced by electric propulsion thruster has a character for high density and low energy, they are quite different from space plasma on geosynchronous orbit. Moreover, charge-exchange ions (CEX) of ion plume the influenced by spacecraft surface potential may form backflow, which would impact the spacecraft surface and make spacecraft surface charging becoming more complicated. Therefore, the ion thruster plume model was established and a numerical simulation using particle-in-cell (PIC) method and Monte Carlo Collision (MCC) model was adopted to obtain CEX ions distribution by plasma simulation software SPIS. The self-consistent electric potential is obtained from neutrality hypothesis. Based on simulation results, the paper calculated the electron and ion charging current, secondary electron and backscattered electron emission current, and built the computation method of the surface charge potential by charge and discharge balance equation. The results suggested that the thruster plasma current mainly accounts reason for spacecraft surface charging when thruster is on work. Moreover, the backflow and neutralization electron current can decrease high surface potential caused by spacecraft charging.