Inductive probe measurements in a rotating magnetic field thruster

Abstract

AbstractThe induced magnetic field during acceleration in a pulsed rotating magnetic field (RMF) thruster is experimentally investigated. A two-axis Bdot probe is employed to characterize the time-resolved evolution of the fields in a 5 kW-class test article. This device is operated at an average power of 4 kW with an RMF frequency of 415 kHz, pulse widths of 125µs, and a repetition rate of 155 Hz. Plasma currents induced in the thruster are shown to reach 2500 A and to have sufficient magnitude to form a field-reversed configuration plasmoid. The Lorentz force resulting from the induced magnetic field contributes ∼25% of measured thrust at this operating condition. Of this Lorentz thrust, ∼58% is due to plasma current interaction with the steady applied bias field, while the remainder is caused by interaction with secondary induced currents in nearby structural elements. This structure force is predicted to scale quadratically with plasma current magnitude. These results are discussed in the context of the historically low performance of these devices and strategies for improving their operation are presented.