Arc-jets are essential facilities used in the research, development and evaluation of thermal protection systems for hypersonic vehicles since they can reproduce the high-enthalpy environments seen during planetary entry. A test campaign is underway in the Hypersonic Materials Environmental Test System arc-jet, in support of the oncoming Mars 2020 mission to screen the response of the PICA-NuSil system. High-fidelity thermochemical non-equilibrium computational fluid dynamics simulations have been carried out to assist the test campaign by simulating the complete test matrix for the facility. A novel approach using machine learning has been implemented in order to calibrate the numerical results to the experimental data available. In addition, three different specimens are analyzed to assess the effect of the geometry on the aerothermal environments and material response. Accurate computational modeling of hypersonic flow fields can help improve the design of thermal protection systems that may enable robot and human exploration of the Moon, Mars, and beyond.