The effect of attack angle on the electromagnetic wave transmission characteristics in hypersonic plasma sheath of re-entry vehicle

The attack angle may greatly affect the hypersonic plasma sheaths around the re-entry vehicle, thereby affecting the transmission characteristics of electromagnetic (EM) waves in the sheaths. In this paper, we propose an in-tegrated three-dimensional (3D) model with various attack angles and realistic flying conditions of radio atten-uation measurement C-Ⅱ (RAM C-Ⅱ) re-entry tasks, for analyzing the effect of the attack angle on the transmis-sion characteristics of EM waves in the sheaths. It is shown that the electron density and collision frequency of the sheath on the windward can be increased by an order of magnitude with the increase of the attack angle. Meanwhile, the thickness of the sheath on the leeward is increased where the electron density and collision fre-quency are reduced. The EM waves are mainly reflected on the windward plasma sheath due to the cutoff ef-fect, and the radio-frequency (RF) blackout is mitigated if the antenna is positioned on the leeward. Thus, by planning the trajectory properly and installing the antenna accordingly during the re-entry, it is possible to provide an approach for mitigation of the RF blackout problem to an extent.