A Novel Engineering Methodology for Decoupled Aerothermal Analysis of Hypersonic Atmospheric Entry

Analysis of TPS response to atmospheric entry is generally performed in a decoupled manner where some terms in the surface balance equations are ignored. In such an ap- proach, surface uxes are calculated using a computational uid dynamics solution of the hypersonics ow ffeld. These are non-dimensionalized for use by a material response code, where correction terms (such as blowing and hot-wall corrections) are applied to account for the missing physics, and surface ablation is estimated with further simplifying assump- tions. A new method is presented here which directly includes blowing and ablation physics, thus removing the need for correction models and simpliffed ablation assumptions. This approach includes the diffusion processes of ablative species in the boundary layer and in- cludes non-equilibrium surface chemistry when appropriate. A comparison is made between the heritage methodology, using a notional trajectory designed to allow molecular disso- ciation and vibrational energy contribution, while not reaching ionizing conditions. The new methodology predicts surface temperatures with the same qualitative trend, with the largest disagreements in areas of the trajectory where non-equilibrium effects are expected to occur. The solid ablation ux and subsequent recession behavior is constantly lower for the new method, but this discrepancy in surface thermochemistry can be decreased by adopting kinetic models with more aggressive oxidation mechanisms. Interestingly, it is found that a large difference in computed recession does not necessarily equate to the largest difference in heat shield sizing.