Numerical Investigation of Hypersonic Atmospheric ISRU Vehicle Inlet on Mars via a Tuned Navier–Stokes Method

Atmospheric in-situ resource utilization (ISRU) vehicles are expected to operate at hypersonic speeds, where low-density, high-enthalpy conditions can drive portions of the flow into the slip regime. In this work, we numerically investigate a hypersonic atmospheric ISRU inlet operating in the Martian atmosphere using Mars conditions from NASA–GRAM at 10 km altitude, and we assess the suitability of a tuned Navier–Stokes (NS) approach in this regime. A local Knudsen-number analysis shows that, although the bulk flow remains continuum, the near-wall region resides in the slip-flow regime, rendering a classical no-slip NS formulation inappropriate. We review the limitations of the classical Maxwell slip condition, highlighting its grid-dependent and potentially unphysical behavior when the local mean free path becomes comparable to the near-wall cell spacing. To address this, we introduce the Continuum–Rarefied Explicit Slip Treatment (CREST), an explicit, mildly dissipative slip-wall model based on a wall-local, projected Knudsen number. Comparisons between untuned NS solutions and CREST-tuned NS solutions demonstrate significant differences in the magnitude and location of peak wall heat transfer and pressure, underscoring the importance of tuned NS formulations with slip-wall models for reliable analysis and design of hypersonic atmospheric ISRU inlets.