Study on Electrodes Design for MPD Thruster Using Water Propellant

• Published in: TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES Vol. 68; no. 2; pp. 108 - 113
• Main Authors: NISHII, Keita, KOMATSU, Daisuke, KAKAMI, Akira
• Format: Journal Article
• Language: English
• Published: Tokyo THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 01.01.2025; 一般社団法人 日本航空宇宙学会; Japan Science and Technology Agency
• Subjects: Discharge; Electric Propulsion; Electrodes; Magnetoplasmadynamics; MPD Thruster; Nozzles; Regolith; Thrust; Thrusters; Water Propellant
• ISSN: 0549-3811; 2189-4205
• DOI: 10.2322/tjsass.68.108

This study addresses a quasi-steady self-field magnetoplasma dynamic (SF-MPD) thruster with water propellant. Water has no toxicity nor reactivity to materials and necessitates no high-pressure tank. Accordingly, using water as a propellant lowers thruster size and the ground-test costs. Moreover, water is abundant on Earth and accessible in space because it may be harvestable in celestial objects such as a regolith on the moon. However, the thrust-to-power ratio of the water MPD thruster was smaller than that of conventional MPD thrusters. Changing the electrode shape is a promising option to improve the thrust-to-power ratio. In this study, a 1-MW class water-propellant MPD thruster was examined to evaluate the relationship between performance and electrode geometry. The ceramic-nozzle anode produced a maximum thrust of 14 N with a corresponding thrust efficiency of 7% and a thrust-to-power ratio of 5 mN/kW at a discharge current of 10 kA. The tubular anode yielded a maximum thrust of 5 N with a corresponding thrust efficiency of 0.8% and a thrust-to-power ratio of 3 mN/kW at a discharge current of 10 kA. The nozzle divergence angle seems to produce gas dynamic thrust, resulting in enhanced total thrust. The difference in discharge path would affect propellant utilization.