Determining Vacuum-Arc Thruster Performance Using a Cathode-Spot Model

Abstract

A simple model of the vacuum-arc cathode-spot and plasma region was developed to predict the performance of vacuum-arc thrusters operating roughly in the arc current range 80–300 A with thrust pulses 250 s. The conventional-based cathode-spot model predicts ion current, average ion velocity, and erosion rate to establish thruster performance. Vacuum-arc properties for a range of materials (Al, Ti, Cr, Fe, Ni, Cu, Ag, Pb, Bi) were determined as well as maximum arc spot currents for Ti, Cr, Fe, Ni, and Bi. Model results generally show good agreement with published data and predicted thruster performance is comparable to literature. Most values of ion-to-arc current ratio were within 10% of published experimental data, ion velocities within about 30%, and erosion rates were within roughly 50%, provided macroparticle ejection was low. The crucial role of the ion-to-arc current ratio on thruster performance is assessed.