Measurement of long-time performance changes of porous electrowetting ionic liquid electrospray thrusters

Porous ionic liquid electrospray thrusters are the ideal propulsion technology for CubeSats because of their structural simplicity, high thrust accuracy and plume self-neutralization. The electrowetting technology can replenish the propellant for the emitter online, thus prolonging the lifetime of the thruster. In order to gain a deeper understanding of its operating characteristics, the changes in thruster performance before and after propellant replenishment deserve to be scrutinized. In this study, the performance changes of a porous electrowetting ionic liquid electrospray thruster are tested by voltage-current test and time-of-flight mass spectrometry over a long operating time. The experimental results show that asymmetric operation with a negative current less than positive current for a long period of time causes anions to compensate for the emission after accumulation at the emitter, resulting in a phenomenon that the negative current is much larger than positive current. The reason for the difference in emission characteristics between the positive and negative modes is that the plume in the positive mode is quite ionized while the plume in the negative mode contains liquid droplets. This study provides a reference for the selection of operating conditions for ionic liquid electrospray thrusters.