Characterization of water propellant in an electron cyclotron resonance thruster

Abstract

A coaxial electron cyclotron resonance thruster operating on water vapor propellant is investigated to determine the influence of molecular propellant chemistry on thruster performance. The performance is characterized at different mass flow rates (0.1–0.4 mg/s) and powers (20–200 W) using a thrust stand, ion energy analyzer, and spectrometer. Experimental data are compared to the results from a theoretical model that includes non-equilibrium chemical kinetics. The thruster is observed to transition from a state where power deposition favors propellant dissociation and ionization into a state where it favors electron heating and ion acceleration. The results suggest that the majority of plasma heating occurs in a core region that surrounds the thruster antenna and that propellant flow outside this region is not efficiently utilized for propulsion.