Alexandra RICHET, Vivien LORIDAN, Pierre BONNEMASON, Luc MIEUSSENS
DOI Number: N/A
Conference number: HiSST-2025-088
Under hypersonic regime conditions, a bow shock surrounds the spacecraft and temperature increases followed by electrons production that makes the gas behave like a weakly ionized plasma. This plasma layer reacts as a shield, either reflecting or capturing electromagnetic waves, leading to radio frequency blackout. The purpose of this work is to identify the most significant aerodynamic phenomena affecting electron density in the flow, and then to determine the resulting signal attenuation by solving electromagnetic equations through the connection between CFD (Computational Fluid Dynamics) and CEM (Computational Electromagnetics) inhouse codes. In the current paper, the multi-species Navier–Stokes equations are employed in the aerodynamic simulations. Due to their low mass, electrons exhibit specific diffusion behavior that cannot be compared to other species and must be carefully modeled to accurately predict their transport around the vehicle. Special attention is given to the parameters and expressions governing diffusion fluxes by including an effective diffusion coefficient, which tends to reduce the electron density along the vehicle wall while increasing electron production at the stagnation front. In a subsequent phase, thermal nonequilibrium is taken into account by incorporating vibrational and electronic internal energy conservation equations into the Navier–Stokes system, each with dedicated source terms. This approach allows the flow to be characterized by multiple temperatures. CEM simulations are then performed to determine the signal
attenuation at the telemetry’s position over its specific frequency to predict RF blackout. To validate the reliability of the coupled CFD–CEM model, simulation results are compared with the RAMC-II experimental data.