Development of a Magnesium and Zinc Hall-Effect Thruster

This paper describes the first demonstrations of a Hall-effect thruster operating on zinc propellant as well as experiments using magnesium propellant. Pathfinding experiments were performed using consumable anodes that were machined from solid magnesium and zinc, which sublimated under the heat load from the discharge plasma and delivered propellant gas to the thruster. The magnesium and zinc anodes served as the acceleration electrode and as the propellant supply. A retarding potential analyzer was used to obtain plume diagnostics during early operation of the experiments, showing acceleration of the propellant ions. A new porous anode with internal propellant reservoir was designed and built to be capable of being refilled with either propellant. A scheme developed earlier for bismuth-fueled Hall-effect thrusters was employed wherein shim anodes were implemented to shift discharge current to and from the main anode to control the main anode temperature and hence the metal propellant sublimation rate. Results are reported showing stable operation of a thruster using a porous anode with magnesium propellant. The magnesium-fueled thruster could be operated for approximately 100 min durations, which was governed by the propellant supply. Also demonstrated was the ability of the shim anode scheme to actively control the propellant mass flow rate from the porous anode. [PUBLISHER ABSTRACT]