3D ablation modeling of silicone-coated heatshield compared to MEDLI2 in-flight data

Abstract

Mars 2020 was protected during atmospheric entry by a heatshield made of Phenolic Impregnated Carbon Ablator (PICA), NASA’s flagship porous ablative material. The heatshield was equipped with the Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) suite that provided detailed in-flight data for the validation of aerothermodynamics models. NuSil, a silicone overcoat that shows a protective effect against atomic oxygen, was applied as contamination control during Mars 2020 assembly, test, and launch operations. A detailed equilibrium ablation and thermal response model of NuSil was developed in the Porous material Analysis Toolbox based on OpenFOAM (PATO) framework. The mass and heat transfer model of NuSil, based on experimental results collected under arc jet environments, includes specific boundary conditions for the coating removal and surface equilibrium processes using representative elements of the NuSil/environment system. Charred NuSil models with different compositions and properties at the surface were investigated. Three-dimensional simulations were performed for the material response of the Mars 2020 heatshield during atmospheric entry. Surface thermal differences were analyzed by comparing PICA-NuSil ablation simulations to in-depth thermocouple data from the MEDLI2 suite.