Thermomechanical Behavior of Damaged TPS Including Hypersonic Flow Effects

The thermomechanical behavior of damaged space shuttle tile thermal protection system (TPS) is considered. The effects of damage on the thermal protection capability and the induced thermal stresses in the TPS are examined by comparing the thermal and structural response of the damaged configurations with the undamaged configurations. The TPS is subjected to the re-entry heating and pressure profile, and the transient temperature distribution and the resultant thermal stresses in the system are computed using finite element analysis. Three different damage sizes are considered. The validity of the simplifying assumptions is systematically examined. Certain assumptions are relaxed and their effects on the system response are determined. Thermal loads based on high speed flow past a cavity are also incorporated to provide a more accurate model. Damage changes the surface properties of the tile, which significantly reduces the radiation heat loss from the surface of the tile. It also alters the flow field and thus the thermal loads sustained by the TPS, resulting in elevated temperatures. The elevated temperatures combined with the stress concentrations induced by the damage increases the thermal stresses. Results indicate that damage is capable of elevating the maximum temperature in the tile to beyond its melting point and cause structural failure.