Measurement research on electromagnetic scattering of turbulent plasma engendered by reentry body shrinkage aircraft model

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.