Fluctuation of arcjet plume properties

Physical properties in a 1-kW hydrogen arcjet plume are observed to fluctuate when power is supplied by flight-type HF switching power electronics. The arcjet power processing unit (PPU) is observed to modulate electron density, electron temperature, and atomic excited state emission. Electron density and temperature are measured temporally by employing a triple Langmuir probe in the arcjet plume. Emission is observed using spectroscopy techniques. Velocity fluctuations are also detected, though they appear not to be directly linked to the PPU frequency. Determination of species velocity using time-of-flight techniques is described, and a connection between the plume emission and the electron temperature is discussed. (Author)