Investigations On Diagnostic Methods Of Distribution Characteristics Of The Plasma Sheath On High-speed Vehicle

During the process of reentry, the aerodynamic heating causes the vehicle surface insulation and the surrounding air thermal ionization, which brings a layer of plasma with special distribution characteristics that envelops the vehicle, called the plasma sheath. Plasma sheath would produce different levels of communication signal reflection or attenuation, which can cause serious communication interruption, the blackout phenomenon. Sheath's effects on communication signals and ways weaken the blackout affected are dependent on the distribution characteristics of the sheath, research on diagnostic methods of the distribution characteristics of sheath is of great significance to the research and weaken the blackout.This paper, diagnose this problem, makes the theoretical analysis and simulation to a variety of diagnostic methods of plasma,combined with the finite-difference time-domain (FDTD) method for the three microwave reflectometry simulation, select the frequency modulation reflection method as diagnostic methods through comparative analysis; finally, according to the characteristics of plasma sheath on high-speed vehicle, frequency modulation reflection method has been improved, and using the improved method combined with finite difference time domain method for different peak electron density, density gradient and collision frequency, sheath models are simulated. The improved frequency modulation method for this problem can more accurately reflect the the electron density distribution profile of plasma sheath with different distribution characteristics, is a suitable diagmostic method for distribution characteristics of plasma sheath on high-speed vehicle.