The Emergency Rescue Of Manned Spacecraft Orbit To Return Re-entry Dynamics Research With The Guidance Problem

In this thesis, the mathematical models of three & six degrees of freedom of manned spacecraft emergency returning non-designed reentry trajectories is described, and the computer model based on SIMULINK is built. The result of numerical simulation has shown the feasibility of the mathematical model and the correctness of the computer model.Then on the base of the computer model, the standard reentry trajectory guidance law is studied, and an approach to obtain the guidance coefficients by modifying the initial value through feedback bias repeatedly is put forward. Simulations have proved the feasibility of the method. The characteristics of the method is that it can modify the guidance coefficients automatically according to the errors between the actual trajectory and the standard trajectory, this is the essential of the standard trajectory guidance. It don' t need any pre-knowledge of the coefficients, this simplifies the problem greatly.Following that, the method of predicting the falling site of the instant retuning trajectory is studied. The factors that affect the trajectory most greatly are induced on assumptions that the earth is spherical and doesn' t circle, according that, a simple formula fit for longitudinal range is derived, and the fitting coefficients is calculated by analytical sampling. The formula is accurate enough, since the maximal error is 12 kilometers, when the reentry velocity is about 7500m/s. Besides, the importance of sample for the accuracy of the formula is also discussed. By comparison of three different formulas obtained by different sampling approaches, it can be found obviously that choosing samples precisely and sufficiently can greatly enhance the accuracy of the fitting formula.Finally, the ulterior work is proposed. The approach of obtaining the guidance coefficients can be utilized in the situations in which more than four coefficients are hired for guidance to enhance the guidance performance. In addition, more precise earth model, which is non-spherical and will circle around its body axis, can be considered, and this will lead to more true results.