Transmission of Radio-Frequency Signals Through Plasma During Hypersonic Flight

Abstract

Abstract : The purpose of the proposed research project was to address the problem of communication black-out with a vehicle during a sustained hypersonic flight. Attempts to communicate through dense plasmas, which forms around an aircraft during hypersonic flight, fail when the transmitted wave frequency is below the plasma frequency. Under such conditions, the transmitted propagating wave becomes evanescent inside the plasma layer and its amplitude is exponentially attenuated. It was demonstrated that without accounting for dissipation, anomalous plasma transparency to radio-frequencies can be achieved via amplification of evanescent waves using a diffraction grating, periodic plasma modulation, or a barrier. For dissipative plasma, adequate transmission can be achieved using a diffraction grating or periodic modulation. Furthermore, using a barrier, reflectionless transmission and absorption can be achieved in dissipative plasma.