Resonant and ground experimental study on microwave plasma thruster

Two types of microwave plasma thruster system setup, one operating at 1-kW power level and the other operating at 0.2-kW power level, are introduced. Only when their thruster cavities are in the resonant state can the microwave energy efficiently produce thrust. According to the test method on the return loss of passive microwave components, the resonance state of thruster cavity is experimented with the scalar network analyzer. The objects are to analyze the cavity efficiency and research the matching condition of the cavity dimension, microwave coupling probe position, and the medium within the cavity. The microwave plasma thruster systems are investigated under the condition of atmosphere. The propellant gas of argon and helium for 1-kW thruster will be ionized to produce thrust under the help of a vacuum pump, whereas the same gas for 0.2-kW thruster will be ionized directly because of the high volume power density. Reflected microwave power from 0.2-kW thruster cavity, mass flow rate, and total efficiency of microwave generation subsystem and cavity are measured, which explains that in order to improve microwave plasma thruster performance the parameters and gas must be chosen properly.