Project HH Atmospheric ISRU Inlet Analysis: CFD Assessment of Shock Managed Hypersonic Intake Geometries

Project HH aims to harvest atmospheric hydrogen for in - situ refueling of deep -space vehicles. Unlike ram - or scramjet intakes that preserve total pressure for propulsion, an ISRU inlet must decelerate the freestream and dissipate as much kinetic energy as possible before encountering the gas -processing hardware. We use CONVERGE CFD with adaptive mesh refinement and SST k-w turbulence modeling to evaluate four axisymmetric inlets under a Uranus reference flow (Mach <10 at 160 km altitude). Case 1, a sharp converging cone, establishes a baseline bow shock, 4.5 kg/s hydrogen capture, and 461,000 N drag. Case 2 verifies that a blunt spherical cap reproduces the similar energy removal and drag, confirming that pressure build-up alone behaves as a blunt fore- body. Case 3 adds a sharp double - cone fore - body: a weak oblique wave precedes the bow shock, producing an Edney Type IV interaction that funnels a supersonic jet into the duct, tripling mass capture to 12.5 kg/s but raising drag proportionally. A half- scale replica (Case 4) sustains baseline throughput while halving drag. Gradient- length Knudsen analysis shows continuum validity over > 95% of each domain. Results provide a first design rule -set: combine an upstream oblique stage with a pressure -induced bow shock to balance energy dissipation, mass flow, and structural load in atmospheric ISRU inlets.