Low power arcjet thrusters are high specific impulse, high specific energy, electric propulsion devices that are now used for north-south satellite stationkeeping. Simple mission considerations indicate that the efficiency of these devices must increase to remain competitive with next generation electric propulsion devices. Numerical performance models can assist in this effort by providing tools to evaluate present performance and new concept designs. To be useful, however, these tools must correctly model the physics of ohmic dissipation, chemical reactions, gasdynamic expansion, and energy transport to and across the anode surface. This paper discusses the sensitivity of model predictions to the description of nonequilibrium transport processes and chemical phenomena within low power hydrogen arcjets. Simulation results are obtained using a continuum-based single fluid description of the flow and with a particle-based Monte Carlo method. Optical measurements of temperatures, velocities, and hydrogen number densities are used to assess the model predictions. Improved descriptions of ohmic dissipation, chemical nonequilibrium, and transport properties throughput the arject flow field are necessary to improve the accuracy of numerical methods and satisfactory represented thruster performance.
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