Aerodynamic Heating In Atmospheric Entry of Space Transportation

“希望”号空间运输系统在进入大气层时遇到的最严重的问题之一是空气动力加热。为了预测气动加热的大小，需要详细的HOPE周围的流动结构。根据HOPE在120km ~ 70km高度的下降飞行轨迹，飞行马赫数大于20。对于如此高的马赫数，机头激波层的温度会大大升高，因此不仅会发生氮分子和氧分子的振动激发，而且可能发生它们的解离。在高海拔地区，由于分子碰撞不足，这些过程将产生非平衡过程。因此，在高海拔地区的激波层流动应被认为是化学上不平衡的。针对这种非平衡状态，采用2温度模型（平移-旋转温度和振动温度），采用粘性激波层法对流场进行了数值计算。建立了具有热化学不平衡的多组分气体流动方程。虽然要考虑的温度是平动、旋转、振动和电子平动温度，但在高海拔地区，由于能量交换不足，振动能与平动能平衡缓慢，振动温度偏离了平动温度。因此需要用振动能量方程来确定振动温度。在中等海拔高度（60km ~ 50km），热力状态处于平衡状态，因此进行化学和热平衡计算，采用1种温度模型。这里使用的模型是一个轴对称的双曲面。此外，在电弧加热的低密度等离子体风洞中，利用少量TPS进行了壁面热流密度实验。

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.