Investigation and experimental simulation of performance deterioration of microwave discharge ion thruster μ10 during space operation

In space operation of the microwave discharge ion thruster μ10 on the asteroid explorers Hayabusa and Hayabusa2, the propellant utilization efficiency deteriorated much more than in the ground endurance test. In this study, a fault tree analysis and experimental simulations of space operation were performed, focusing on the grid-derived internal carbon contamination. It was found that the performance deterioration due to the waveguide contamination matched that in Hayabusa2 qualitatively and quantitatively. Based on the experimental verification, the future performance is experimentally predicted. •Performance deterioration investigation for microwave ion thruster μ10 in space.•Fault tree analysis showed possible cause: grid-derived carbon contamination.•Experiments revealed carbon on waveguide decrease propellant utilization efficiency.•Successful thruster performance reproduction in “Hayabusa2” operation by experiment.•Prediction of future thruter performance based on experimental verification.