| A scaling methodology was created for the purpose of designing high-power, high-current, xenon-fueled Hall thrusters. This scaling methodology was based on preserving the plasma processes inherent in Hall thrusters that function at discharge currents in the range of 4.5 to 10 Amperes operating at discharge voltages in the range of 200 to 700 Volts. In order to preserve these plasma processes a simplified theory of Hall thruster operation was developed that described these plasma process in terms of Hall thruster characteristics including discharge channel width and depth, magnetic field strength and distribution, and propellant density. This theory was implemented to design a fifty kilowatt Hall thruster capable of operating at a discharge current of 100 Amperes.; It was determined that high power Hall thrusters require peak centerline radial magnetic field strengths of 200--300 Gauss, comparable to conventionally sized thrusters. The axial distribution of the applied radial magnetic field was determined to require both a step gradient upstream of the Hall region and to have little or no effect in the vicinity of the anode. High power Hall thrusters were determined to require xenon propellant densities achievable with anode mass flow rates of approximately 0.10 mg/s per square centimeter of channel cross-sectional area. Discharge channel depths of 20--30 mm were required to enable electric field strengths and electron temperatures required for efficient ionization. Channel widths compatible with the required axial gradient of the applied radial magnetic field were necessary. A 2:1 ratio of wall magnetic field strength to centerline magnetic field strength provided these conditions. The ratio of discharge-chamber-volume-to-surface-area was not optimized even though this ratio is known to influence electron temperature as a result of secondary electron emission. |
