0-D composition and performance analysis of an air-breathing radiofrequency ion thruster

This paper presents a physics-based 0-D steady-state model of a radiofrequency ion thruster (RIT) that is valid for any propellant blend, and hence, any plasma mixture, and the model is used to predict the drag compensation capability and plasma composition of an air-breathing RIT operating in very-low Earth orbit (VLEO). This study fills a gap in the modeling of air-breathing electric propulsion with an air-breathing RIT model that is validated with experimental data of a RIT operating with an N_2 / O_2 mixture. The model expands upon current 0-D RIT models by accounting for the dissociation of neutral molecules and molecular ions and by applying particle conservation for each ion and neutral species. Atomic oxygen in the atmosphere is assumed to completely recombine into O_2 in the collector, and the model is used to calculate an air-breathing RIT’s thrust, discharge efficiency, mass utilization efficiency, and discharge plasma composition at altitudes between 80 and 150 km. At 1 kW of total input power and an optimal flow rate of 0.17 mg/s, the net thrust was limited to 3 mN at all altitudes considered. At these same operating conditions, the mass utilization efficiency and discharge efficiency were approximately 0.15 and 870 eV/ion, respectively. To increase the performance of the thruster, the magnetic field should be increased in order to increase the beam current. The mole fraction of atomic oxygen in the discharge chamber was found to be between 0.19 and 0.27 depending on the altitude, indicating that grid erosion should be a focus of future studies.