Study on the plume self-neutralization of ionic liquid electrospray thruster based on median potential

Ionic liquid electrospray thruster (ILET) has the advantages of high specific impulse, precise thrust control, and low structural mass, which make it ideal for small satellites. The charged particles of ILET’s plume may lead to device charging or even damage, restricting its engineering applications. Thus, this paper examines the self-neutralization effectiveness of the ILET's plume under various emission conditions using particle-in-cell simulations. In order to accurately evaluate the self-neutralization effectiveness of the ILET’s plume, the median potential is explained in this paper and its reasonableness as the evaluation criterion for self-neutralization of the plume is verified. The working envelope for achieving self-neutralization of the ILET’s plume is determined by simulating the bipolar plume under various emission conditions. The results indicate that when the highest and lowest potentials are the same, the mean electric field strength between two points in space with a better degree of neutrality is 200% higher compared to points with a lesser degree of neutrality. The study determines the working envelope to realize self-neutralization of the ILET’s plume with an effectiveness of 70%. When the emission voltage of the anode thruster is fixed, the range of the cathode thruster’s voltage ranges from 108.36 V to 228.74 V. The asymmetry between the anode and cathode emissions of the ILET prototype significantly influences the operational range of the cathode thruster. Greater asymmetry leads to a narrower operating range for the ILET to achieve self-neutralization of the plume. This study serves as a guide for the ILET to achieve self-neutralization of the plume.