Two-Dimensional Aerodynamic Loads of Space Shuttle Thermal Protection System Considering Steady Internal Flow

The Thermal Protection System (TPS) in Space Shuttle is assembled by the ceramic tile, the strain isolation pad (SIP) and the substrate structure. The existent experiment data reveals that the pressure distribution in the gaps and in the SIP has important effect on the aerodynamic load of the tile. Restricted by the computational capacity decades ago, an approximated multi-tile flow model based on the porous media flow was proposed to analyze the aerodynamic load for Shuttle tiles. The present work utilizes computational fluid dynamic (CFD) technology to reexamine the effects of steady internal flow on the aerodynamic load of the tile. The two-dimensional TPS model is established by adding tile-SIP assembly on the surface of airfoil. The far-field flow speed is assumed at transonic regime to simulate the critical load condition with shock wave on the tile. The internal flow in the gaps and flow through the SIP are calculated by solving the Navier-Stokes equation. The Spalart-Allmaras turbulence model is adopted. The pressure distributions on the top of the tile, in the gaps and along the bond line between the tile and the SIP are obtained. Numerical results show: The strongest aerodynamic load is at Xs/L = 0.67; when the permeability of SIP is increasing, the moment in Z-direction and the force in Y-direction are decreasing and the force in X-direction is increasing.