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The finite volume time domain (FVTD) method is proposed to accurately calculate the electromagnetic (EM) scattering of hypersonic vehicles coated with non-uniform plasma sheath. The plasma sheath in the actual flight environment is accurately established by solving the Navier–Stokes equations and combining appropriate thermochemical models. The radar cross section (RCS) of metal and uniform medium coated metal targets calculated by FVTD are in good agreement with those simulated by the software FEKO (MoM) and the Mie series. The calculated RCS of the vehicle under the reentry condition is consistent with the flight test data, too. The calculated electron number density distribution is consistent with the flight experiment results. The body fitted structure EM grid is adopted. The EM grid independence of the target coated with plasma sheath is studied. Then, the scattering and plasma EM parameters of the vehicle during the actual reentry are studied. The reentry altitude is from 78 to 55 km, and the reentry velocity is from 6406 to 6350 m/s. With the reentry altitude decreasing, the plasma angular frequency and collision frequency increased gradually. The scattering of different incident conditions and different wall catalytic conditions is analyzed in depth. This paper provides a valuable reference for vehicles' detection, recognition, and stealth during reentry flights. [ABSTRACT FROM AUTHOR]

It is important for the design of radio communication system to understand the plasma distribution in high-temperature flowfield. A numerical method to simulate the complicated plasma flow field around a hypersonic flight vehicle is developed by solving the Navier-Stokes equations with thermo-chemical non-equilibrium source terms. The method is validated by comparison of the distribution of electron number densities with flight experiment. The effects of chemical reaction and thermo-chemical nonequilibrium model the wall temperatures and catalytic activities on the computational results are studied. The distribution of plasma in flow over a lifting body are investigated too. The results show that the electron number densities computed by seven-species and eleven-species chemical model are different obviously when the flowfield temperatures beyond 10000K, and in the case O+ must be taken into account in chemical reaction models besides NO+. The wall conditions, especially the catalytic activities, have a more important effect on the distribution of plasma, the reliable data of the wall catalytic activities, have a more important effect on the distribution of plasma, the reliable data the wall catalytic activities, have a more important effect on the distribution of plasma, the reliable data of the wall catalytic activities, have a more important on the distribution of plasma, the reliable data of the wall catalytic activities and temperatures must be obtained firstly in order to simulate exactly the plasma flow over a lift body. [ABSTRACT FROM AUTHOR]

Aero-optic effect induced by the flow-field outside the IR seeker optical window is one of the problems needed to be solved in designing a high-speed interceptor. When IR signatures form the target throughout the high-speed flow-field, the IR image on the seeker will be shifting, blurring and even jittering. These effects bring errors of position-setting, and degrade the intercepting precision. Based on the thermochemical non-equilibrium Navier-Stoke equations, the high-speed flow-field is simulated numerically. The Ray-tracing and physical-optic methods are used to get the OPD and PSF, which can describe the shifting and blurring of IR image. The affect factors of IR image shift and attenuation are considered, including Mach number, attack angle, altitude, incidence angle and IR wavelength. As a result, the aero optical effects under 30km altitude have obvious influence on IR imaging, and increasing the incidence wavelength can reduce the attenuation of IR image intensity. [ABSTRACT FROM AUTHOR]

In order to design thermal protection system, it is important to predict heat transfer rate precisely on the hypersonic vehicles. In present paper, considering chemical reaction, interal energy excitation and thermo-chemical non-equilibrium effects of high temperature air, the thermo-chemical non-equilibrium flow-fields are simulated using the numerical code AEROPH_Flow. An aero physical numerical code system for Hypersonic vehicles, the distributions of heat transfer rate is obtained, and the analysis is done for the influence of the chemical reaction model, thermodynamic non-equilibrium model, surface temperature, surface material catalytic action on the computational results. The results show that thermo-chemical non-equilibrium models have a more important influence on the computational results, it is important for the selection of the correct air reaction model and thermal non equilibrium model according to the flight environment and thermo-chemical non-equilibrium mechanism of the flow field around the hypersonic vehicles; the heat transfer rate isn't always the highest for lower surface temperature, and it become very complicated for the variation law of heat transfer rate along with the surface temperature under the condition of high Mach number or thermo-chemical non-equilibrium flow, so the surface temperature may as well be fixed choosed according to the distribution of the real flight condition or different constant for computing exactly heat transfer rate on the hypersonic vehicles. [ABSTRACT FROM AUTHOR]