ARCJET ENGINE PERFORMANCE- EXPERIMENT AND THEORY
Analytical and experimental results are presented on the propulsion performance and the energy addition and loss mechandisms of a radiation-cooled arcjet engine having a constricted-arc configuration. A useful lifetime of one month was obtained with such an engine operated with hydrogen at 1000-sec specific impulse, 30-kw d-c power input, andd an electric to thrust power conversion efficiency of 40%. At 30-kw input power, reliable engine operation was obtained at up to 1000-sec specific impulse with ammonia and up to 1500-sec specific impulse with hydrogen. Specific impulses greater than 2000 sec were obtained using hydrogen in a radiation-cooled engine operated at 200-kw input power. Electric to thrust power conversion efficiencies were in the range from 35 to 45%. Visual examination of the arc discharge through a quartz constrictor indicated that there was a smooth, constant-diameter, luminous core extending from the cathode through the constrictor and terminating in the nozzle. Examination of experimental cool-off data and engine exterior surface temperature distributions indicated the existence of an energy transfer path from the hot engine walls to the cold incoming propellant. (auth)