Spacecraft charging due to lack of neutralization on ion thrusters

Abstract Lack of neutralization is one of the most common malfunctions in ion thrusters. This phenomenon has been investigated by means of a ground experiment using a 2-cm class microwave-discharge ion thruster together with a reduced-size mock-up of the MUSES-C spacecraft. Electron leakage from the plasma beam to the high-voltage solar array has been observed to cause a slight amount of charging, its magnitude being equivalent to the operational voltage of the solar arrays. In the cases with no electron emission for ion beam neutralization, full-charging was established and the extracted ions were observed to return to the thruster body. At such experimental conditions, a so-called “virtual anode” appears in front of the deceleration grid. In this research, design guidelines for both the spacecraft and the ion engine system are proposed, based on the experimental simulation results.