Investigation of stabilized resonant cavity microwave plasmas for propulsion

Results are presented for the performance of a microwave electrothermal thruster utilizing bluff-body and swirling flow stabilized plasmas with helium and nitrogen propellant. Stabilized plasmas have been produced in the TM(011) electromagnetic cavity mode with coupling efficiencies approaching 100 percent and specific powers up to 27.3 MJ/kg. Fluid dynamic measurements indicate specific impulses of up to 543 s, efficiencies of 44-69 percent, and thrusts of 0.27-0.40 N with helium propellant. Spectroscopic results indicate plasma core electron temperatures of 11,840-12,170 K with extremely flat radial profiles. (Author)