The Study Of THz Wave Transmission Characteristic In Plasma Sheath

When A spacecraft entering the Earth's atmosphere,the velocity of reentry is very fast,Generally speaking,it faster than sound velocity dozen times even several tens of times,the spacecraft is surrounded by the fierce shock waves when it in the step of reentry.The air molecules in the shock waves become dissociated and ionized by high temperature and high pressure,and become a dense layer of plasma enveloped the spacecraft.The plasma has absorption and reflection effects on the waves transmission because of its special electrical properties.We call this phenomenon “communications blackout”,which is leaded by plasma that is produced in the step of reentry.The plasma surrounded the spacecraft we call plasma sheath.For the “communication blackout”,this article simulates some plasma sheaths of the blunt spacecraft— RAM-C? in different conditions,and researching the transmission properties of THz waves in the plasma sheath on this basis.Basing on the research conclusions give some reasonable suggestions about using the THz communication technology to relieve “communication blackout”.CRAM-First,this article discuss the meaning of research “communication blackout ”,domestic and foreign research on this problem,accounting related work and research method about this article briefly.Second,introducing the physical properties of unmagneized cold plasma,the specific forming process of the plasma sheath and the flow properties in the five plasma sheath regions.Third,describing the algorithm of simulating electromagnetic waves—Scattering Matrix Method(SMM).Using this algorithm simulate the THz waves transmission properties in the plasma sheath and researching the relationships between transmission properties and angle ?? electron collision frequency ?e?thickness of plasma sheath X?electron density peak N0.Proposing some physical explaining based on the interaction theory of plasma and electromagnetic wave.Finally,according to the flight parameters of RAM-C? from the NASA flight report,simulating several plasma sheaths of RAM-C? in different situations depended on the plasma fluid computing simulation language and the open source platform NRLMSISE-oo.And then,simulating the microwaves and THz waves transmission properties in these plasma sheaths by using scattering matrix method.At last,discussing the feasibility,which THz communication technology as a measure to relieve “communication blackout”,and offering some specific suggestions.