Study On Electromagnetic Scattering Characteristics Of Hypersonic Vehicle In Plasma Sheath

During the reentry capsule reenters the atmosphere and the hypersonic aircraft travels in extended space,due to its high Mach number and the particle distribution inside the space,the surface of the aircraft rubs with the particles in the air,and some heat-resistant materials outside the aircraft react chemically.Some surface materials are dissociated at high temperature,and a high-temperature substance is formed on the surface of the aircraft,namely plasma.The plasma sheath will affect the positioning of the ground and the aircraft.The presence of the plasma sheath has a serious impact on target detection.There may even be a flight accident.At present,for the aircraft,its main solution to interfere with radar signal processing through plasma is the store-and-forward technology.This method can only store part of the information of the aircraft,but it cannot monitor the target aircraft in real time.Although for the return module,the detection failure caused by the sheath is only a few minutes to tens of minutes,but for the aircraft that performs continuous missions in a continuous space for a long time,due to its at least reentry cruise time,it is The loss of contact may be as long as ten minutes.Because these aircraft need to maintain communication with the ground all the time,it is very important to locate the radar in real time.The main work of the paper is as follows:1.Simulation Study of Plasma Sheath Chemical Flow Field.The fluid simulation software FLUENT under CFD was used to simulate the thermochemical non-equilibrium flow field around the hypersonic aircraft.Firstly,the basic concepts of the flow field control equations were introduced,and the hypersonic vehicle model was established.Components and reaction equations and basic information of the aircraft.The flow field grid was established using GAMBIT,and the flow field at different flight heights and Mach numbers was simulated.The different flight heights and Mach numbers were compared and analyzed for the temperature,air five components and electrons in the flow field around the aircraft Effect of density distribution2.Study on Electromagnetic Scattering Characteristics of Space-time Heterogeneous Plasma Sheath of Hypersonic Vehicle.In this chapter,the Z-transformed FDTD(Z-FDTD)method is used to calculate and analyze the blunt cone aircraft at different altitudes,Mach numbers and angles of attack,and different incident wave frequencies and different incident wave angles when the plasma sheath space is not uniform.The change of the RCS doublestation angle simulates the different change functions of electron density in the plasma sheath over time including growth,attenuation,and Gaussian and rate of change.The influence of the time-varying rule of electron density on RCS is analyzed.In the case of a uniform plasma sheath and a slowly increasing electron density,different flight conditions and different plasma parameters include different heights,Mach numbers and angles of attack,different cyclotron frequencies,different incident wave frequencies and different incident wave angles.The effect of the two-station RCS of the aircraft verified the influence of the "magnetic window effect" on the electromagnetic scattering characteristics.3.The JE convolution-finite-difference time-domain(JEC-FDTD)formula was derived for oblique incident plasma current density convolution.The Mur absorption boundary and connection boundary in the case of oblique incidence were modified.The obtained flow field data analyzes the changes in reflectance,transmission coefficient,and absorptivity when the electron density changes with time,the rate of change in electron density,the number of flying Mach,and the height of the electromagnetic wave obliquely incident on the plasma at different angles of incidence.Influence,calculated the two-station RCS values of different polarization states when the electromagnetic wave enters the plasma-covered blunt cone aircraft,and finally developed a visualization software based on the winform platform to complete the interaction between the electromagnetic wave and the plasma-covered aircraft.