Optical Measurements of Density and Species Concentration in a Low Reynolds Number Micro-Nozzle Flow

摘要

With increasing interest in CubeSats and low power micro-propulsion, there is a need to increase the efficiency of micro-nozzles. In order to design optimal nozzles, computational models must be validated against detailed studies of the nozzle plume structure. This paper describes the development of a system to measure species concentration, density, and temperature in the exhaust plume of a micro-resistojet nozzle at the rarefied gas conditions encountered by a CubeSat in orbit. Raman and Rayleigh scattering techniques are to be used to measure these quantities for nitrogen (N_2), hydrogen (H_2), and a mixture of N_2 and H_2 to simulate decomposed ammonia (NH_3). The thruster will be tested at a range of Reynolds numbers (Re) from 100 to 3000, and gas reservoir temperatures from 300 K to 1000 K.