Studies of Terahertz Wave Propagation in Realistic Reentry Plasma Sheath

Abstract

Abstract-Communication 'blackout' is a big challenge for modern space engineering. In the recent decade, the terahertz (THz) technology is believed to be an effective solution for the 'blackout' problem. Many research works about the transmission of THz waves in plasma slabs have been carried out. According to those works, the radio attenuation of THz waves in plasma slabs strongly depends on thickness of the slab, electron density, electron collision frequency and temperature. However, few previous works have paid attention to realistic reentry plasma sheath. In the present paper, a hypersonic fluid model is introduced in order to investigate the structure of the realistic plasma sheath which covers a blunt coned vehicle. The scattering matrix method is employed to study the transmission of THz waves in realistic plasma sheath. According to the present study, the wave frequency, electron density and collision frequency are the most significant factors which determine the attenuation of the THz waves in the plasma sheath. Since the whole plasma sheath is inhomogeneous, to install the antenna at an appropriate position helps mitigate the 'blackout'. For the blunt coned reentry vehicle, installing the antenna on the wall close to the bottom is helpful for mitigating the 'blackout' problem.

Studies on the Effect of Angle of Attack on the Transmission of Terahertz Waves in Reentry Plasma Sheaths

“…The model is developed based on the Navier-Stokes (N-S) equations and gas molecular theories [10,12,13]. The conservative form for the N-S equations is given below: All the variables are defined in Table 1.…”

“…The air 7-species model was developed by NASA. σ, Ω, f , c P i and c V i in Equations (7) to (10) are given by the 7-species model as well.…”

“…Those parameters depend on the aerodynamic shape and flight condition of the vehicle [8,9]. The factors which significantly impact the THz waves' transmission in a realistic plasma sheath are not identical to those in presumed plasma slabs [10]. Therefore, in order to solve the 'blackout' problem with THz scheme, it is necessary to study the transmission properties of THz waves in realistic plasma sheaths rather than that in presumed plasma slabs.…”

Design of Sub-THZ Beam Scanning Antenna Using Luneburg Lens for 5g Communications or Beyond

“…Some of the measurement techniques at sub-THz frequency bands were discussed in [7,8]. The works advancing in THz frequency [9,10] range also have high significance for the future communication applications.…”

Sub-THz signals’ propagation model in hypersonic plasma sheath under different atmospheric conditions

“…The communication blackout would occur if the signals that reach the antenna is too weak to be detected. Moreover, the propagation of sub-THz signals in realistic hypersonic plasma sheaths could be different from that in presumed plasma slabs since all the parameters of a hypersonic plasma sheath vary simultaneously [9]. It implies that the propagation of sub-THz signals in hypersonic plasma sheaths could be much more complicated than that in plasma slabs.…”