Research On Reentry Dynamics And Guidance Of Manned Deep Space Exploration

This dissertation studies Manned Deep Space Exploration (MDSE) reentry dynamic characteristics, reentry trajectory optimization approaches and reentry guidance based on manned lunar missions. The main results achieved in this dissertation are summarized as follows:MDSE reentry dynamic characteristics are studied. (1) The equations of motion for atmospheric reentry are formulated and a program using MATLAB is developed to solve them. (2) The differences between MDSE reentry and LEO reentry missions are analyzed; (3) MDSE reentry modes are compared, so are the Earth capture approaches; (4) The trajectory characteristics are analyzed under different initial conditions and bank angles. Some conclusions which could be useful in future MDSE missions are proposed by analyzing the simulation results.A reentry trajectory optimization approach using Gauss Pseudospectral Method (GPM) is studied. (1) The dissertation studied the theories and formulated the models for MDSE reentry trajectory optimization, including the dynamic model considering the rotation of the Earth, the constraint models and the optimization objective; (2) Aimming at deficiencies of traditional trajectory optimization method in initial value determination and computation efficiency, a pipelining and segmenting trajectory optimization approach based on GPM, containing an initial guess generator, is proposed. Then this approach is applied to compute the optimal trajectories of reaching a point target of MDSE reentry flight. The feasibility of this approach is validated by analyzing the results.Two reentry guidance laws are studied and proposed based on predetermined path following concept and PredGuid concept for MDSE missions. (1) The nominal linear bank angle approach is put forward to design a reference trajectory for which the initial bank angle is solved by Newton Raphson algorithm. Large numbers of trajectory simulations are carried through to evaluate the performance of the guidance; (2) Numerical Predictor-Corrector (NPC) Guidance is studied. The absolute value of bank angle is determined using the secant method, and the sign of it is reversed whenever the cross range exceeds the velocity-dependent deadband. A guidance law is proposed based on NPC and the performance of it is evaluated by analyzing the trajectory simulation results. (3) The performances of the two guidance laws which are mentioned hereinbefore are compared.In conclusion, some reseach has been done in MDSE reentry. The models, methods, simulation programs, simulation results and the conclusions in this dissertation can be references in future manned lunar missions.