The Calculation Of Terhertzwave Propagate In The Plasma

Hyper sonic flying machines(warhead, aerocraft, re-entry capsule, etc.) speed up to Mach dozens when returning to earth’s surface. Because of the violent friction leads high temperature and high pressure. The surrounding air is ionized into a plasma state. It will generate a layer of plasma sheath around flying machines surfaces when they into the atmosphere. The plasma sheath absorbs the energy of the reflected electromagnetic wave, and the Doppler frequency shift and the phase shift of the electromagnetic wave are generated. The ionized air interferes with radio signals, framing signals and navigation signals. That is the blackout.( Blackout are caused by an envelope of ionized air around the craft, created by the heat from the compression of the atmosphere by the craft.) The flight mission and astronauts’ safe are seriously threatened by blackout phenomenon.Terahertz wave can be effectively used in the function of the electromagnetic wave and optical wave can not be realized, due to terahertz wave has of a dual characteristic- both terahertz wave and electromagnetic wave. Terahertz wave can effectively overcome the blackout phenomenon which caused by plasma. It has been proved in theory. In this paper, we study the interaction of the plasma sheath on the surface of the aircraft from two aspects. Firstly, we can use commercial software CFD-FASTRAN for simulation of flow field. According to three dimensional chemical non equilibrium flow Navier-Stokes governing equation to simulate the distribution of plasma flow field around the Soyuz craft. And they can get plasma pictures around the spacecraft, electron density images, pressure cloud pictures, temperature field cloud pictures and collision frequency cloud pictures. In order to let us to have a whole understanding on the plasma flow field. Then, we find the smallest part of the plasma electron density to provide theoretical basis for the installation of communication antenna.Finally, this article makes a study of the propagation characteristics of communication radio in the plasma. It takes the theoretical formula derivation of electromagnetic wave propagation in the plasma about Z transform time-domain finite-difference method. And then we use the Z transform time-domain finite-difference method to do numerical simulation and interpretation for the power reflection coefficient and transmission coefficient of terahertz wave in the plasma changing with working wave frequency, collision frequency, plasma electron density and plasma thickness’ s changing. It goes from the perspective of simulation that terahertz wave propagation in the plasma sheath within relationship between the power reflection coefficient, power transmission coefficient and plasma electron density, collision frequency, plasma thickness, electromagnetic wave frequency respectively. The simulation results show that the terahertz wave effect in solving the blackout significantly.