Efficiency Analysis of a Low Discharge Voltage Hall Thruster

Abstract

Power loss mechanisms for a 2 kW (nominal) Hall thruster operating at low discharge voltages were examined through thrust stand measurements and probe studies. Operating conditions included discharge voltages ranging from 100 V to 300 V and mass flow rates of 3 to 5 mg/s of xenon. Thrust stand measurements indicate a minimum thrust efficiency of 15% at 100 V at 3 mg/s and a maximum of 59% at 300 V and 5 mg/s. Retarding potential analyzer, emissive and Faraday probes were utilized to quantify multiple sources of inefficiency. The ratio of exhausted ion current to discharge current was found to be the dominant loss mechanism at low discharge voltage.

Energy Efficiency in Low Voltage Hall Thrusters

“…These magnet current values are comparable (to within .25 A) with the values used in the preceding study. 3 Figure 2 depicts the current to the anode as a function of the magnet current. The current efficiency is the ratio of discharge current to mass-flow current multiplied by the ionization charge quantity f i Q.…”

“…3 The study was conducted as a function of discharge voltage where thrust efficiency was calculated from thrust stand data, discharge supply measurements, and propellant line flow rates. The operating point corresponding to maximum efficiency was found by adjusting the current through the magnet coils.…”

A Vaporizing Liquid-Metal Anode for High-Power Hall Thrusters

“…Bismuth thrusters in Soviet research utilized a propellant feed system that was maintained in excess of 1,000 0 C, in order to flow gaseous bismuth directly into the thruster. 24 Additionally, the thruster body was heated above 1000°C using resistive heaters. This method may present a problem, however, in that a number of heaters consuming significant amounts of power are likely required.…”