Use Of Large Planar Plasma Sheets For The Study On Communication Blackout Effects Of Hypersonic Vehicles

Vehicles, such as satellites, space shuttle, intercontinental missiles and spacecraft, in the earth and other planets atmosphere reentry process, and the critical space hypersonic vehicles which were developing in the word’s major powers in recent years, will still suffer the flight risk caused by communication blackout effects in the future for a long time. Since the high cost of flight test for communication blackout effects, this paper constructed a set of communication blackout effect simulation system on the ground. Comprehensive study was made on the diagnosis of plasma parameters and electromagnetic wave propagation characteristics. Use of the simulation system, preliminary experimental experiment research was carried out to optimize plasma sheath open scheme of the existing mitigation means for communication blackout effects. Main work and results are as follows:(1) Designed modular linear hollow cathode and made a double groove modular linear hollow cathode according to that design. The scheme and working principle of communication blackout effects simulation system employing modular and fixed size linear hollow cathode was introduced. Two schemes for generating plasma photonic crystals utilizing the modular linear hollow cathode were introduced to promote the popularization and application of the designed modular linear hollow cathode.(2) Designed an electrostatic probe and developed the automatic probe data processing software. In order to diagnose the parameters’ time- space distribution characteristics of communication blackout effects simulation system, the rotating hollow cathode method, fast frame method and sliding electrostatic probe method were designed. Using the plasma parameters in the thickness direction and vertical direction, the evolution process of plasma characteristic parameters’ three dimension distribution was recreated. Studies have shown that large area planar plasma sheets had similar characteristic parameter values and distribution characteristic with the plasma sheath, and can be utilized to study electromagnetic wave propagation characteristics of plasma sheath.(3) Variable control experiment was carried out to get the parameters’ time- space distribution for different pulse discharge current, pressure and magnetic field. Based on that experiment result, IV the influence factors of plasma characteristic are analyzed. Because of the complexity of the plasma characteristic parameters influencing factors, to facilitate the rapid setting parameters to generate the required plasma, after simplifying the ground blackout plasma parameters in simulation system of 3-D distribution model, the concept of plasma parameters database was put forward.(4) Using plasma layered model and simplified model of the distribution of plasma parameters of three-dimensional transverse field propagation matrix formula for magnetized plasma sheet was deduced. Based on numerical calculation results, the transmission characteristics of electromagnetic wave in plasma sheet during the pulse discharge process was researched. It showed that in order to facilitate the blackout effect simulation system to simulate the "blackout" effect, the plasma sheet in the first 100 μs was better. The incident electromagnetic wave frequency should be lower than the critical frequency of the plasma sheet, and its polarization direction can either perpendicular to the direction of the magnetic field is parallel to the magnetic field direction. If the frequency of incident electromagnetic wave frequency within the upper hybrid wave resonance absorption frequency, polarization direction perpendicular to the direction of the magnetic field is better.(5) Using the measured electron density distribution data and the transverse field propagation matrix formula, the effect of pulse discharge current, pressure, magnetic field and plasma slice thickness on the electromagnetic wave propagation characteristics of the ground blackout effect simulation through numerical calculation. The results show that in order to facilitate the blackout effect simulation system to simulate the "blackout" effect, can adopt the following methods: add a suitable magnetic field, appropriately increase the plasma sheet thickness, air pressure, increase pulse discharge current.(6) Based on the established ground communication blackout effect simulation system, under the guidance of aperture coupling theory, preliminary experimental experiment research was carried out to optimize plasma sheath open scheme of the existing mitigation means for communication blackout effects. The preliminary study results showed that the electromagnetic wave whose polarization direction parallel to the wider edge and frequency is greater than the gap’s resonance frequency could be more easily propagated through the aperture of the plasma sheath. The gap’s resonance frequency depends on the crack opening width, the smaller the width, the bigger the resonant frequency.