Performance characterization of a low power hall thruster operating with xenon-nitrogen mixture propellant

Abstract

The present study deals with the performance characterization of a 300 W-class Hall thruster operating with xenon-nitrogen mixture propellant and its plasma diagnostics to investigate the physics behind the Hall thruster. Hall thrusters are highly efficient electric propulsion device that generates thrust by the electrostatic acceleration of ions produced by the collision between neutral particles and ExB confined electrons. In the performance characterization of the Hall thruster operating with xenon-nitrogen mixture, the thrust, specific impulse, and anode efficiency were measured at the fixed anode power (250 – 450 W) with selected anode voltage (200 – 400 V). As a result, the performance, including the thrust, specific impulse, and anode efficiency, deteriorated with the increase in nitrogen mass fraction of propellant and improved with the increase in anode power. At the anode power of 450 W, the anode voltage of 300 V, and the nitrogen mass fraction of 40%, the thrust, specific impulse, and anode efficiency decreased by 31%, 16%, and 16%p, respectively, compared to pure xenon operation. However, the xenon mass flow rate decreased by 53% compared to pure xenon operation, implying the viability of xenon-nitrogen mixture propellant in terms of providing options to reduce the propellant cost. Furthermore, a thrust analysis model is formulated to identify the major cause of performance deterioration. The measured thrust and results from plasma diagnostics, including a Faraday probe and a retarding potential analyzer, were utilized in the analysis. As a result, the decreased propellant ionization, especially reduced production of Xe$^+$ ion, was the major cause of the performance deterioration. Additionally, pure nitrogen operation was achieved at the anode power of 450 W and anode voltage of 350 V, implying the potential of a low-power pure nitrogen Hall thruster. Advanced plasma diagnostics will be conducted to understand the contribution of individual ion species to the performance and physics of the Hall thruster operating with xenon-nitrogen mixture and pure nitrogen. Further performance improvements of the pure nitrogen Hall thruster are also planned.