Spacecraft Reentry Period Of Wave Characteristics And Magnetic Field To Reduce Black Barrier Effect Research

Functional and fine communication system is indispensable and crucial during reentry process, which guarantees the safe landing of reentry capsules. Nevertheless, reentry plasma is produced due to shock compressions and viscous heats encountered by reentry capsules at hypersonic speed. The plasma is nothing less than a special conductive medium, which will drastically interact with radio waves and have a fatal effect on its propagations as a result, even give rise to blackout phenomenon within several minutes. In this condition, communication performance not so much only depend on the property of wireless equipments of capsules as need to take the adverse environment of radio waves fully into account. Therefore, the impacts of plasma on waves should be considered and dissected in advance before investigating the reentry communication technology, and then grope for expedient and advisable mitigations and alleviations on plasma effects. Only in this way can communication deterioration and its quality be favourably improved.Firstly, theoretical foundation of plasma physics and plasma sheath theory is briefly introduced in this thesis.Secondly, the wave propagations in reentry plasma has been systematically investigated adopting analytic methodology in macrography:(1) electromagnetic wave attenuation constant is simulated by means of MATLAB at first, then the special effect of collision frequency on radio waves has been illustrated emphatically based on the simulations;(2) the derivations of scattering matrixes for wave propagation in nonmagnetic and inhomogeneous plasma is also performed theoretically;(3) In addition, the main research is to concentrate both on vertical and oblique incidence in nonmagnetic and homogeneous plasma, and power absorption coefficient and power reflection coefficient of electromagnetic waves are formulated and simulated respectively employing MATLAB;(4) Further more, transmissison characteristics though reentry plasma is also simulated and analyzed. Meanwhile, the relevant universal interfaces have been designed based on MATLAB GUI platform for more intuitionistic and entire calculations of radio wave propagation property in the plasma.Thirdly, on the basis of the propagation property we have just discussed, communication performance of radio wave through plasma is briefly exemplified in MPSK system, on proposing reentry channel model in plasma, the bit error rate of each M at different reentry height is deduced and caculated, but the result can not be pulished completely for it has been confined in an unauthorized patent with the code of201218002827.8. Finally, the feasible mitigation solution to plasma effect exploiting magnetostatic field is elaborated:a calculation model with the advent of magnetic field is initially proposed; Moreover, complex permittivity tensor in magnetized plasma and corresponding attenuation constant are deduced respectively, then universal interfaces using MATLAB are also developed to simulate each attenuation characteristics of left-hand and right-hand circular polarized waves in homogeneous plasma at the reentry height of80Km、70KKm、60Km and50Km, and the magnetic field density needing to abate reentry plasma attenuation (even below2dB) has been calculated out; then transmissison characteristics though reentry plasma in the presence of magnetic field is also simulated and analyzed at each reentry height. The result indicates that strong magnetic field does make microwaves impervious to plasma, especially for right-hand circular polarized wave.What we have accomplished will definitely provide a theoretical foundation for the applications of the gorgeous manned spacecraft projects through plasma sheath.