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Ablation of a thermal shield covering a supersonic vehicle can change the characteristics of the plasma sheath, inevitably affecting the propagation of incident electromagnetic waves. The effect of ablation of the heat shield coating in the radio attenuation measurement-C (RAM-C) vehicle on the Vivaldi antenna radiation is quantitatively analyzed for the first time in this article. Ray tracing is used with an integrated model of an ablative plasma sheath and an X-band Vivaldi antenna to obtain the disturbed electric field for a thermal protection layer with different ablation parameters. Numerical results show that the ablation parameters of the thermal protection layer strongly affect the antenna performance. Ablated particles with higher densities and bigger radii cause more energy attenuation of the incident waves. This conclusion can provide a quantitative reference for the study of thermal shield materials.

The electron density distribution of plasma is an important parameter to study the effect of plasma on electromagnetic wave attenuation. However, to obtain the electron density distribution accurately, it is necessary to calculate the electron temperature of plasma first. The calculation methods of plasma electron temperature are mostly affected by the thermodynamic equilibrium state, but the calculation methods of electron collision cross section are not affected by the thermodynamic equilibrium state. A high-voltage electromagnetic coil was designed as a plasma excitation source to generate inductively coupled argon plasma in a cylindrical cavity. The emission spectra of the plasma inside the cavity were recorded, and the plasma electron temperature was calculated based on the spectral data and the electron collision cross section model. A parameter fitting method was proposed to fit the argon characteristic spectral lines and excited state energy parameters for improving the calculation method of the electron collision cross section. Finally, the method was validated using the Boltzmann graphical solution. The obtained numerical results and variation trends of the electron temperature are consistent with the results of the Boltzmann diagram solution method. This is because multiple eigen-spectral lines were considered in the calculation. The results obtained from the calculations are more stable and have fewer errors than those obtained from the improved electron collision cross section method. Moreover, the calculation of plasma electron density is not affected by the thermodynamic equilibrium state, which makes it more widely used.