The aerothermodynamics of the gas giant planets was studied in a superorbital expansion tube. A mixture of H2/Ne was used as a substitute to the Jovian atmosphere of H2/He, which allowed Jovian entry aerothermodynamics to take place at flight speeds of 15 km/s, whilst still maintaining chemical similarity. Results for shock standoff distance and electron concentration along the stagnation streamline of a blunt body demonstrated that nonequilibrium effects occurring in the vehicle shock layer during Jovian entry can be experimentally simulated. Two-wavelength and near-resonant holographic interferometry were used to obtain experimental results.
A one-dimensional inviscid analytical model was developed to model shock layer property distribution along the stagnation line of a blunt body in nonequilibrium hypersonic flow. Shock standoff was calculated from the average density along the post-shock stagnation line and controlling non-dimensional flow parameters were identified. The analytical model was validated for dissociating flow using published theoretical, experimental and CFD shock standoff results. For ionising flow, experimental results for shock standoff and electron concentration distribution were compared with predictions from the theoretical model. Good agreement was obtained for shock standoff results using near-resonant holographic interferometry, however, for two-wavelength holographic interferometry, experimental results were consistently lower than predictions, primarily due to low resolution of density variation in the shock layer. Shock standoff distances modified for the effect of low density resolution showed significantly improved agreement with both analytical and CFD results. The experimental electron concentration distribution was reasonably consistent with the analytical model. Radiative cooling of the shock layer, three-dimensional cylinder end effects and uncertainty in reaction rate coefficients were identified as second-order effects that may contribute to differences between predictions made using the analytical model and CFD, and experimental results.
New scaling parameters have emerged during analysis that can be used to simplify the experimental simulation of hypersonic nonequilibrium dissociating and ionising gas mixtures. Flow properties along the shock layer stagnation line were found to depend primarily on the chemical scaling parameter for highly nonequilibrium flight, regardless of individual values of freestream density, freestream velocity, freestream dissociation, body radius and degree of gas dilution.