Effect of Nonuniform Plasma on Grid Erosion of the Water Ion Thruster

Miniature water ion thrusters provide CubeSats with orbit transfer capability and enable missions that require high [Formula: see text]. Erosion on the grids is critical for the thruster’s lifetime and propellant utilization efficiency. It was shown numerically that the nonuniformity of the plasma in the discharge chamber causes inhomogeneous erosion of the grid. However, deviation from experiments was still a problem. In this study, we evaluate the performance and the change in the grid erosion of the miniature water ion thruster during 1000 h of operation. The propellant utilization efficiency decreases from 16% to 12% due to grid erosion. The contamination effect of the antenna and magnets on the performance of the thruster was less than that due to the change of grid geometry. In terms of grid erosion, in the center and the periphery of the grid where the ion beam density is low, the direct impingement of the ion beam is dominant, and the diameter of the accelerator grid eroded from 0.31 to 0.52 mm. On the other hand, in the middle part of the grid, where the ion beam is dense, charge exchange ions dominate the erosion, and the diameter was eroded from 0.31 to 0.39–0.45 mm in hexagonal.