Surface catalysis effects on mitigation of radio frequency blackout in orbital reentry

Abstract

Radio frequency (RF) blackout during atmospheric reentry leads to the cutoff of communication with ground stations and/or data-relay satellites. This causes significant problems during reentry, and thus, mitigation methods have been in high demand. In this study, we numerically demonstrate a novel method for mitigating the RF blackout using surface catalysis effects. Plasma flow behavior and electromagnetic wave propagation around a reentry vehicle were investigated in detail. The approach couples computational fluid dynamics and a frequency-dependent finite-difference time-domain method. The computations were performed with a massive parallelization technique using a large computer. The computed results were compared for cases imposing low and full catalysis conditions on a surface boundary. The investigation revealed that the surface catalysis effects reduce the RF blackout. Atomic species, dissociated across a shock wave formed in front of the vehicle, were recombined on the vehicle surface through surface catalysis. These molecules, flowing into a wake region at the vehicle’s rear, caused recombinations of electrons, originally generated in the shock layer. Therefore, a decrease in electrons was observed in the wake region and a wake path, which allows the propagation of electromagnetic waves, was formed. This complicated behavior of the molecules and electrons, induced by the surface catalysis, resulted in mitigation of the RF blackout.