Research On EHF Signal Transmission Characteristics In The Plasma Sheath Of A Sharp Cone Hypersonic Vehicle

"Blackout" has always been a problem in the aerospace,the formation mechanism is that when a hypersonic vehicle is flying at high speed in nearby space,the plasma sheath generated by the gas surrounding the vehicle interacts with the shock wave,which will greatly attenuate the electromagnetic wave communication signal and even interrupt the communication.There is no mature and universal solution to this problem.This article starts with the method of "change the appearance of the vehicle " and uses the "electromagnetic adjustment method" to study the transmission characteristics of the EHF signal in the plasma sheath of the sharp cone hypersonic vehicle,this method combines "high frequency communication" and "magnetic window method".And using the same research process to qualitatively discuss the navigation application of Beidou signals on reentry vehicle.The main research contents are as follows:1.Through the establishment of a hypersonic fluid dynamics model,the plasma sheath structure of the blunt cone vehicle and the sharp cone vehicle is compared,including the electron density distribution in the sheath,the electron collision frequency distribution,and the evolution of the sheath,the evolution time of the sheath and the thickness of the sheath.Based on the above parameter data,the scattering matrix method is used to solve the transmission characteristics of the EHF signal in the sheath.It is found that in the sharp cone vehicle sheath,the signal attenuation mechanism is determined by the absorption mechanism and reflection mechanism of the signal.The attenuation mechanism in the sheath of a blunt cone vehicle is quite different.In the sheath of a blunt cone vehicle,the contribution of the signal reflection mechanism to the signal attenuation is almost zero.2.Based on the data obtained from the EHF signal under different magnetic field strengths,two solutions are proposed to deal with the black barrier problem faced by the sharp cone hypersonic vehicle.One is to use 140 GHz signals for real-time communication and data transmission without adding auxiliary equipment to the aircraft to generate a constant magnetic field.The second method is to use the94 GHz signal for real-time communication under the 0.15 Tesla intensity magnetic field generated by the auxiliary equipment,and explain the advantages and disadvantages of the two solutions.3.Under the same research process of plasma sheath channel characteristics,qualitatively discuss the navigation application of Beidou signal on reentry vehicle.It is concluded that the Beidou signal can be applied to the navigation application of the reentry vehicle when the flight speed is 10 Ma and no external magnetic field is applied.Similarly,when the flight speed is 12 Ma,the magnetic field strength is 0.1Tesla,the flight speed is 14 Ma,and the magnetic field strength is 0.5 Tesla,the Beidou signal can be used as a navigation signal for the reentry vehicle.In summary,this article provides a theoretical basis for the use of EHF signals to deal with the blackout problem of the hypersonic vehicle,and tries to apply the Beidou signal to the related blackout problem to analyze and solve the blackout problem.It is of great significance.