Thermomechanical Behavior of a Damaged Thermal Protection System: Finite-Element Simulations

Abstract

The thermomechanical behavior of damaged space shuttle tile thermal protection system (TPS) is simulated using the finite-element method. The effects of damage on the thermal protection capability and the induced thermal stresses in the TPS are evaluated by comparing the thermal and structural response of the damaged configurations with the undamaged configurations. The TPS consists of three components (the LI-900 tile, the strain isolation pad, and the underlying structure), and it is modeled as a discrete, three-layer structure. The TPS is subjected to the reentry heating and pressure profile corresponding to the Access to Space vehicle. The transient temperature distribution and the resultant thermal stresses are then computed. Three different sizes of damage simulating hypervelocity impact are considered. The validity of the simplifying assumptions used in an earlier study is systematically examined to determine the correct combination of assumptions required for modeling this class of problems. Influence of damage location on TPS response is also studied and it is concluded that centrally located damage represents a worst-case scenario.