A Terahertz Signal Propagation Model in Hypersonic Plasma Sheath with Different Flight Speed

A hypersonic plasma sheath could shield communication signals, which results in the so-called “blackout.” Hypersonic flights in near space used to suffer from the “blackout.” Terahertz (THz) communication is considered to be a potential solution to the blackout problem. On the other hand, it is still not clear that how the complex flight conditions impact the THz communication channel conditions in the plasma sheath. The relation between the occurrence of communication blackout and the flight conditions is unclear either. In the present study, the relation between the THz signal attenuation in plasma sheaths and the hypersonic flight speed was investigated using the numerical hypersonic hydrodynamic model. According to this study, the thickness of the plasma sheath decreases with the increasing flight speed. The electron density and the electron collision frequency increase with the flight speed. As a result, the THz signal attenuation increases with the flight speed. In addition, a new estimation model, which is able to predict the THz signal attenuation in the plasma sheath for arbitrary flight speed, was developed on the basis of the numerical study. The estimation model, in which the hypersonic hydrodynamics is absent, could help to significantly reduce the time consumption in predicting the THz communication channel conditions as well as the occurrence of the blackout.