介绍了在弹道靶上利用二级轻气炮发射再入体缩比模型开展湍流等离子体电磁散射特性模拟试验方法、湍流等离子体的雷达散射截面积(RCS)测量方法.给出了模型尾迹湍流等离子体的电磁散射特性测量典型试验结果,对获得的试验结果进行了分析,并与一阶畸变波Born方法计算结果进行了比较.结果表明:合理选择缩比模型发射速度和飞行环境压力,在弹道靶上能够模拟产生湍流等离子体;利用激光阴影成像技术获得的锥模型尾迹流场图像证实了尾迹转捩的出现及其湍流形成;在给定的试验条件下,锥模型及其绕流RCS测量值比其尾迹RCS测量值高3个数量级,比背景散射电平高0.5~2.5个数量级,且信号没有周期性,幅度脉动范围为1～15 dB,频率脉动范围0.4～40 kHz;锥模型湍流尾迹RCS的脉动可能是尾迹电子密度的脉动引起的;单站X波段雷达系统测量的锥模型尾迹亚密湍流等离子体的散射信号测量值与计算结果变化规律一致;弹道靶RCS测量技术可用于再入体缩比模型湍流等离子体电磁散射特性研究,为开展相关研究提供了一种有效的地面模拟实验研究途径.

This paper presents experimental methods to simulate the turbulent plasma around shrinkage aircraft models launched by a two-stage light gas gun and measure its electromagnetic scattering characteristics.Experiments of simulating the turbulent plasma around the hypersonic models are carried out in the ballistic range.The Radar Cross-Section(RCS)measuring methods of the turbulent plasma engendered by the models are introduced.Typical electromagnetic scattering properties obtained in the tests are demonstrated.The experimental results are compared with the calculated results acquired by the first-order distorted wave Born methods.It is found that the turbulent plasma is properly simulated when the models are launched under the conditions of appropriate velocity and pressure.The transition and turbulent wakes are designated in the flow field images of the models acquired by the laser shadowgraph technique.The electron density of the turbulent plasma wake is lower than the critical electron density corresponding to the incident radar wave.The measured RCS signals of the models and the around flow field are three orders of magnitude larger than that of the wakes.The measured echo signals are not periodic.The amplitudes of fluctuations range from 1 dB to 15 dB.The frequencies of the fluctuations range from 0.4 kHz to 40 kHz.The RCS fluctuations of the shrinkage aircraft models are possibly caused by the presence of electrons in the turbulent plasma wakes.The scattering signals intensity of the undercritical turbulent plasma wakes is much larger than those of the backgrounds.The RCS measurements show a good agreement with the calculated results.The RCS measurement technology adopted in the ballistic range tests can be used to investigate the electromagnetic scattering characteristics of the turbulent plasma engendered by hypersonic shrinkage aircraft models.