Backward Scattering Characteristics of a Reentry Vehicle Enveloped by a Hypersonic Flow Field

Abstract

The hypersonic flow field around a reentry vehicle has a significant influence on the ground-vehicle communication as well as on the detection and recognition of the reentry vehicle. Backward scattering characteristics of a reentry vehicle enveloped by a hypersonic flow field are analyzed using a high-order auxiliary differential equation finite difference time-domain (ADE-FDTD) method in this paper. Flow field parameters, including electron density, neutral particle density, and temperature, are obtained by solving the Navier-Stokes (NS) equations numerically. According to the flow field parameters, distributions of the plasma frequency and the collision frequency are then derived. Based on a validity of the physical model and the high-order ADE-FDTD method, backward radar cross sections (RCSs) of a perfect electrical conductor (PEC) sphere enveloped by a hypersonic flow field under different Mach numbers, heights, and incident angles of the electromagnetic (EM) wave are then investigated. Numerical results show that the incident angle of the EM wave exerts noticeable effects on the backward RCS, which is due to an inhomogeneous distribution of the plasma. The flight height and Mach number have significant influences on the distribution of the plasma that they play an important role in the variation of the RCSs. The results presented in this paper provide useful reference data for practical tests in ballistic range or in the high-frequency plasma wind tunnels, where a sphere target is usually used due to its simple shape.

The Measurement of Radar–Plasma Signatures in a Hypersonic Shock Tunnel: Simulation and Experiment

“…where (11) represents the average thermal velocity of the electrons and ( 12) the respective collision integral with Gupta's correlations for electron reactions (index e) with particle species (index i) in high temperature air [14]. The remaining variables denote the frequency f of the considered electromagnetic wave, the translational component of the temperature T t , the electron charge e, electron number density n(e − ), the electric field constant ϵ 0 , the electron mass m e , Boltzmann's constant k B and the electron temperature T e .…”

“…Besides radar signatures of hypersonic targets, also the study of the radio communication blackout during the atmospheric re-entry is an important application area. First, considering the plasma sheath as layered medium with constant plasma values in each layer [5], [6], [7], [8], second, applying ray tracers [9], and, third, solving the electromagnetic wave propagation in plasma with rigorous numerical approaches like Finite Difference Time Domain (FDTD) solvers [10], [11], [12], [13]. These solutions, however, are not exact and use some approximations like a rectangular grid in usual FDTD schemes or require further assumptions like the absence of a magnetic field to simplify the considerations.…”

An Asymmetrical Mixed Higher-Order Discontinuous Galerkin Time Domain Method for Electromagnetic Scattering from the Plasma Sheath around a Hypersonic Vehicle

“…In recent years, hypersonic weapons near space have played an increasingly important strategic role in warfare. When a hypersonic vehicle reenters the atmosphere, ablative hypersonic viscous fows produces a plasma sheath [1,2], which is a nonuniform plasma fow composed of free electrons, ions, and neutral particles around hypersonic vehicles [3,4].…”