Global modeling and performance analysis of a water-fueled radio-frequency gridded ion thruster

Abstract

This study presents a global model analysis of a water-fueled gridded ion thruster powered by a radio-frequency inductive coil. A comprehensive reaction set is developed to capture the complex plasma chemistry of water, including the formation and ionization of secondary neutrals generated through dissociation and neutral–wall recombination reactions. The global model solves coupled particle and energy balance equations to predict plasma properties and thruster performance as a function of operating parameters, such as the input radio frequency power and the propellant mass flow rate. The results demonstrate that while water exhibits a greater discharge complexity than xenon, the dissociative pathways contribute only marginally to the formation of light ions, such as H+ and H2+. The discharge is instead dominated by heavier ions, such as H2O+, O+, and OH+, which contribute to meaningful thrust production. Compared with xenon (for a 12-cm diameter thruster studied here), water exhibits higher electron temperatures and an enhanced coil–plasma power transfer efficiency, although the propellant mass utilization efficiency and the thrust-to-power ratio are lower. A thrust performance analysis reveals that water can achieve a competitive thrust and specific impulse at higher input powers, establishing its viability as an alternative propellant. Overall, the model provides a robust foundation for the development of future water-fueled electric propulsion systems and addresses a critical gap in general low-temperature water plasma research.