Arcjet Modeling for Efficient Characterization of Thermal Protection System Materials in a CO2-Rich Environment

The ablative heat shields on recent Mars missions had less surface recession than predicted. This deviation has been attributed to the NuSil coating that was applied to prevent particle shedding. Experiments have since shown that this coating behaves differently in a Mars-like atmosphere (rich in CO2) than it does in an Earth atmosphere where it was initially assessed. A test campaign was conducted in 2024 at the Hypersonic Materials Environmental Test Systemat NASA’s Langley Research Center to assess NuSil coating in a Mars-like environment. To quantitatively analyze the material response, heat flux and stagnation pressure on the test specimens are required. Due to the differences between the test specimen and the measurement probes, these must be computationally determined using boundary conditions that also must be computationally determined. The purpose of this work is to apply an efficient approach of running computational cases with boundary conditions spanning the range of the experimental campaign in order to construct surrogate models to map probe measurements back to upstream boundary conditions. These surrogate models are then utilized to determine the appropriate boundary conditions for all of the experimental measurements without the need for computationally expensive iteration used in past work. For the experimental cases considered, inlet pressures are predicted with about +2/-3 kPa average uncertainty, and inlet enthalpies are predicted with about +0.6/-0.4 MJ/kg average uncertainty. The results also show that the top contributors of uncertainty are O catalytic efficiency for the high heat flux cases and CO2-CO2 diffusion cross section for the low heat flux cases.