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The rough structure may affect the flow field and electromagnetic (EM) scattering characteristics of a hypersonic vehicle. In this study, the EM scattering characteristics of the hypersonic vehicle RAM C-II with a microrough surface were investigated in the millimeter wave band. We first simulated the flow field of a smooth RAM C-II vehicle and calculated the radar cross section (RCS) in the wideband using the physical optics method. The calculation results show that many factors contribute to the variation in the RCS; however, it is occasionally difficult to predict. We then used a one-dimensional Gaussian random rough surface to generate a RAM C-II with a microrough surface through a point-coordinate transformation and simulated its flow field. The electron density flow field of the rough surfaced aircraft fluctuates greatly on the wall. Finally, we calculated the RCS of RAM C-II with different values of roughness in the millimeter wave band. The change of surface structure can be reflected in millimeter waves, and the RCS is determined by both plasma and rough structure. [ABSTRACT FROM AUTHOR]

A new electromagnetic (EM) calculation model, the inhomogeneity zonal medium model (IZMM) (based on the physical optics (PO) method), is proposed to calculate and analyze the EM scattering characteristics of hypersonic vehicle covered with a plasma sheath. First, the flow field of the plasma sheath is divided into nonuniform calculation subregions with different spacing sizes. The shape of the external flow field of the aircraft is modeled by fitting with a paraboloid and circular platform with different radii. Then, the electron density, temperature, and pressure distribution are obtained by collecting data from different points in the flow field of the sheath. Finally, a piecewise PO method is used to calculate the backscattering radar cross section (BRCS) of the hypersonic vehicle covered with plasma sheath from $L$ -band to $X$ -band. The numerical results show that the EM scattering characteristics of a target spacecraft covered with a plasma sheath can be described more accurately by using zoned medium model simulation. Under different flying conditions, the BRCS of hypersonic vehicle covered with a plasma sheath appears to be reduced to different degrees in the $S$ -band and the band range of 7–11 GHz, and a large attenuation of BRCS occurs in the head area of the aircraft. The research results enrich the EM modeling method of hypersonic vehicles, overcome some shortcomings of the existing PO method, and provide technical support and innovative ideas for the accurate analysis of the EM scattering characteristics of hypersonic targets. [ABSTRACT FROM AUTHOR]

To investigate the electromagnetic scattering problem related to a foil in a turbulent hypersonic plasma environment, the scattering field formulas for hypersonic plasma turbulence were improved by applying the anisotropic power spectrum. Using the theory of electromagnetic scattering of a conducting object, the second moment of a conducting object's scattering field is obtained in the hypersonic plasma turbulence. Finally, the backscattering cross-section of the foil surrounded by the hypersonic plasma turbulence was calculated. The results showed that the fractal dimension led to an increase in the complexity of the hypersonic turbulent structure, and thus had a greater influence on the electromagnetic wave scattering. The scattering cross-section of the foil in the hypersonic turbulence decreases rapidly. Meanwhile, the anisotropic parameters in the model represent scale-dependent stretching of the turbulent eddy. As the anisotropic parameters of the turbulence increase, there will be less scattering of the hypersonic turbulence. At this point, the total scattering cross-section of the foil in hypersonic plasma turbulence increases gradually. By improving the aerodynamic shape of the aircraft, it can produce a large number of anisotropic turbulent eddies which can effectively improve the passive jamming capability when the foil is cast. [ABSTRACT FROM AUTHOR]

3-D time-varying and spatially nonuniform plasma is applied using the finite-difference time-domain algorithm in investigating the effects of electromagnetic (EM) wave scattering in the plasma sheath. The plasma sheath is stratified in space, and three types of electron density in time-varying forms are assumed. The characteristics of different time-varying forms are analyzed using radar cross section (RCS). In addition, the effects of RCS change with time at S - and L -bands are investigated using electron density as the time variable. In the condition of time-varying and spatially nonuniform plasma sheath, the attenuation of EM wave is affected by different time-varying regularities of electron density ( ne ). The RCS varying with time is related to the change rate of ne . [ABSTRACT FROM PUBLISHER]

Based on the detection platform of space-borne radar (SBR), the dynamic electromagnetic (EM) scattering characteristics of a hypersonic vehicle covered with plasma sheath are calculated and analyzed by the physical optics (PO) method. Using the angle-time conversion method, the dynamic radar cross section (DRCS) of the vehicle in horizontal flying path and different flying states is solved in the range of L-band to X-band. The relevant effective statistical features are extracted from the time-scale matrix of DRCS based on continuous wavelet transform (CWT). The numerical results show that: At different flying altitudes, the backscattering radar cross section (BRCS) of the hypersonic vehicle covered with plasma sheath has irregular fluctuation and large range reduction in the head region of the vehicle. Generally, the higher the incident EM wave frequency is, the more detailed the fluctuation characteristics of the DRCS can be reflected. Within the same radar illuminate angle range, the time consumed by the vehicle DRCS is inversely proportional to the flying height and flying speed and is directly proportional to the detection altitude of the SBR. Besides, the different kinds of statistical eigenvalues extracted from DRCS will play an important role in hypersonic targets classification and recognition. [ABSTRACT FROM AUTHOR]