Antenna radiation characteristics of wake region in ablative plasma flow

When the wall temperature of the thermal protection or insulation materials on the surface of an aircraft exceeds their tolerance limits under the heating of supersonic aerodynamic heat energy, degradation damage phenomena such as high-temperature thermochemical ablation and mechanical erosion will occur in the surface area. The ablation diffusion products (ablation particles) generated are ejected into the surrounding plasma flow field and suspended around the aircraft, forming a hypersonic plasma flow field with ablation diffusion substances. The presence of ablation diffusion substances can significantly affect the physical and electromagnetic characteristics of the original plasma flow field. To solve this problem, this study establishes a coupled electromagnetic model of an ablative plasma flow field surrounding a blunt-nosed cone aircraft and analyzes the antenna radiation characteristics in the wake region of the ablative flow field. The research method consists of several key steps. Firstly, the plasma flow field around the blunt-nosed cone is simulated using ANSYS FLUENT, a computational fluid dynamics (CFD) software. This step provides the fundamental flow field parameters such as electron density, temperature, and pressure distributions. Secondly, ablation particles, generated from thermal protection material degradation, are uniformly dispersed into the plasma flow. Then, the ablative plasma flow field is obtained. Thirdly, an X-band horn antenna is designed in ANSYS HFSS and loaded into the center of the wake region of the ablative plasma flow field. Based on the above models, the ray-tracing method is employed to quantitatively evaluate the attenuation of antenna radiation as it propagates through the wake region. The numerical results demonstrate that the plasma flow field enveloping the aircraft induces significant attenuation of antenna radiation energy. It is more noteworthy that the presence of ablation particles within the flow field substantially amplifies this energy dissipation effect. Both the ablation particle density and size distribution are identified as dominant factors controlling radiative energy loss, exhibiting proportional relationships with the attenuation of the incident field. This study systematically proves the influences of ablation particle density and size on initial field energy attenuation. This research can provide a reference for solving the problem of electromagnetic wave propagation that causes the information transmission bottleneck of near-space hypersonic aircraft. It can also serves as a theoretical basis for further in-depth research on technologies such as target detection, identification, thermal protection/insulation materials, and system design of hypersonic aircraft.