Laser-induced fluorescence measurements of flow velocity in high-power arcjet thruster plumes

The flow velocity of atomic hydrogen in the plume of an ammonia-propelled arcjet thruster was measured using laser-induced fluorescence (LIF). The velocity was obtained by the Doppler shift of the absorption peak of the Balmer α spectral line. Measurements were made at the nozzle exit, varying the distance from the plume centerline. Results are presented for arcjet operating conditions 13, 20, and 27 kW with a mass flow of 0.31 g/s