100 kW hydrogen arcjet thruster experiments

The High Power Arcjet thruster is investigated with respect to the effects of constrictor diameter, cathode gap, and cooling mechanism on specific impulse and general engine performance. The thruster is mounted on a thrust balance and integrated into a stainless steel vacuum chamber, and cathodes with 5-, 10-, and 14-mm diams and varying tip configurations are tested. The results are analyzed with specific attention given to cathode erosion, varied propellant-injection angles, the influence of tank pressure, and pressure data for the arc chamber. The thruster with a 4-mm constrictor is more critical than the 6-mm version, and the best results are obtained for the 4-mm cathode gap. The highest specific impulse for this configuration is 1300 s at 200 mg/s corresponding to an input power of 66 kW. The smaller throat diameter is shown to lead to better performance characteristics for the High Power Arcjet thruster. 8 refs.