Modeling ablation of charring heat shield materials for non-continuum hypersonic flow

We describe the on-going development of physical models for use with the direct simulation Monte Carlo (DSMC) method that allow the injection of pyrolysis gases generated by the ablation of charring thermal protection system material for flows in translational nonequilibrium. The test case used in the study is the Stardust reentry capsule, which employed a Phenolic Impregnated Carbon Ablator (PICA) heat shield and experienced very high heat loads during its descent through the atmosphere of the Earth. We systematically examine the effect of improving the level of sophistication of the physical models used for chemical reactions, surface temperature, and ablative mass flux on the predicted flowfield and surface properties.