Preliminary Characterization of an MPD Thruster with Extended Anode and Multichannel Hollow Cathode

Abstract

Magnetoplasmadynamic thrusters (MPDTs) are coaxial devices that utilize Lorentz forces to accelerate a plasma discharge. Such devices are capable of processing high power (from 100s or kW to multi-MW per device) and are or interest for future spacecraft propulsion applications. However, the performance of these thrusters is limited by the "onset" instability condition, in which radial pinch forces deplete the anode region plasma, resulting In high anode fall voltages and excessive erosion beyond a characteristic current level. A new MPDT was developed utilizing a multi-channel hollow cathode with an extended anode and multi-channel hollow cathode. The thruster was tested in the "quasi-steady" mode with argon propellant at 1.5, 1.0, and 0.6 g/s mass now rates. The thruster was operated initially in the self-generated magnetic field mode, and data are presented on the voltage-current response characteristics to identify early indicators or transition to the MPD "onset" instability in this geometry. This work serves to prepare for later experiments to compare results with various externally-applied magnetic fields to investigate the influence of the magnetic field on the characteristic current for the onset condition.

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