Aerodynamic Heating In Atmospheric Entry of Space Transportation

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One of the most serious problems which space transportation system "HOPE" encounters is aerodynamic heating during atmospheric entry. In order to predict the magnitude of the aerodynamic heating, the detailed flow structure around HOPE is required. According to HOPE's descent flight trajectory at the altitudes from 120km to 70km, the flight Mach number is larger than 20. For such ultimately high Mach numbers, the air temperature in the shock layer of the nose is highly increased, so that not only vibrational excitation of nitrogen and oxygen molecules but also their dissociations possibly take place. These processes will be generated as nonequilibrium process at high altitudes due to insufficient molecular collisions. Thus, the shock layer flows at high altitudes should be considered to be chemically out of equilibrium. For such nonequilibrium state, the flow field was numerically calculated with viscous shock layer method using 2 temperature model (translational-rotational temperature and vibrational temperature). The equations were formulated for a multicomponent the gas flow with thermal and chemical nonequilibrium. Although the temperatures to be considered are translational, rotational, vibrational and electron-translational temperatures, at high altitudes vibrational temperature deviates from translational temperature due to slow equilibration of vibrational energy with translational energy because of insufficient energy exchange. Therefore the vibrational energy equation is needed to determine the vibrational temperature. At moderate altitudes (60km to 50km), thermodynamic state will be in equilibrium, and therefore chemical and thermal equilibrium calculation was carried out and 1 temperature model was used. The model used here is a axisymmetric nyperboloid. In addition, experiments of heat flux to the wall using a few of TPS were performed in an arc-heated low density plasma wind tunnel.