Computational Predictions of the Hypersonic Material Environmental Test System Arcjet Facility

Abstract

The Hypersonic Materials Environmental Test System arcjet facility located at the NASA Langley Research Center in Hampton, Virginia, is primarily used for the research, development, and evaluation of high-temperature thermal protection systems for hypersonic vehicles and reentry systems. To improve testing capabilities and knowledge of the test article environment, a detailed three-dimensional model of the arcjet nozzle and the freejet portion of the flowfield is developed. The computational fluid dynamics model takes into account nonuniform inflow state profiles at the nozzle inlet as well as catalytic recombination efficiency effects at the probe surface. The results of the numerical simulations are compared to the calibrated pitot pressure and the stagnation-point heat flux for three test conditions at low, medium, and high enthalpies. Comparing the results and the test data indicates a partially catalytic copper surface on the heat flux probe of about 10% recombination efficiency and a 2–3 kPa pressure drop from the total pressure measured at the plenum section in front of the nozzle. With these assumptions, the predictions are within the uncertainty of the stagnation pressure and heat flux measurements. The predicted velocity conditions at the nozzle exit are also compared and show good agreement with the radial and axial velocimetry data.