Erosion and passivation of electrodes of a magnetoplasrnadynarnic thruster

Abstract

The erosion of the electrodes in a low powered steady state magnetoplasmadynamic thruster is described. The environment experienced by the electrodes in this device is harsh, leading to high cathode erosion rates and, when operating with propellants containing oxygen, passivation of the anode. The erosion of the electrodes is often cited as the lifetime limiting feature of magnetoplasmadynamic thrusters, and can also interfere with the operation of these devices when they are used for non-propulsive applications. The cathode erosion was investigated using analysis of the surface structure, theoretical evaporation predictions, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and metallographic examinations of the crystal structure. The passivation of the anode was investigated using SEM and EDS techniques. From this work suggestions for reducing the erosion rate are made. A plasma coating application of this device for materials deposition is also suggested.