Numerical investigation of surface catalytic effect on the plasma sheath of a hypersonic re-entry capsule

Radio frequency blackout indicates the communication interruption between signal monitoring sites and re-entry vehicles; it is a serious threat to the safety of astronauts and the space exploration missions. In this study, a surface catalytic model coupled with a thermochemical non-equilibrium computational fluid dynamic model is developed to study the catalytic wall effect on the plasma sheath of a hypersonic re-entry vehicle. The mechanism of the surface catalytic effect on the plasma sheath of a re-entry capsule is revealed by a comparative study. The flow-field characteristics simulated under conditions of the full-catalytic and non-catalytic walls are compared and discussed for the hypersonic atmospheric re-entry capsule at different altitudes. The chemical and physical mechanisms behind the surface catalytic effect of the re-entry capsule are analyzed. The experimental data of Radio Attenuation Measurement-C-II are used to validate the numerical model established in the present study. It is found that the numerical results simulated with the fully catalytic wall are more consistent with the experimental data. Near the capsule wall, the mole fractions of the species N, O, N+, and O+ decrease as the catalytic recombination coefficient increases. Because of the surface catalytic effect, the communication black is mitigated due to the reduction of the electron number density in the wake zone of the capsule.