Performance Predictions for CW-Mode Operation of an RMF Thruster

Abstract

The performance of a $\sim$4 kW-class rotating magnetic field (RMF) thruster operating in CW-mode is analytically predicted. Scaling arguments based on a first-principles analysis are employed to translate experimental measurements of electron density, electron temperature, and current density from triple Langmuir probe and inductive probe measurements of pulsed operation into equivalent values for CW operation at the same mass flow rate and applied bias field strength. Measurements are considered from thruster operation at combinations of 45 and 60 sccm Xe and 120 and 180 G peak centerline bias field. It is predicted that while the transition to CW-mode operation would reduce power draw by $\sim$30\% while increasing efficiency by a factor of 3-5, the overall efficiency will remain below $6\%$. The low CW-mode performance is driven primarily by wall interactions, with the majority of thrust arising from electron pressure at the walls and the majority of thermal losses arising from electron wall losses. These results are discussed in the context of design strategies to improve performance.