Research On Optimization Methods And Applications Of Finite Thrust Trajectory Transfer

Along with the rapid progress of the science and technology and the development of the aerospace missions, the finite thrust trajectories mission is drawing more and more attention from the public. The injection of the geo-stationary satellite, the outer planet exploration and the revisit of the moon have been implemented or listed in the timetable. Because of the high specific impulse, the finite thrust propulsion system increases the mass percentage of payloads, economizes the cost of missions and adds the scientific gains. However, new demands are brought up for the technology of trajectory optimization.With the background of the optimal trajectory transfer at the apogee of Geosynchronous Earth Orbit(GEO) satellite and the optimization of Earth-Mars finite thrust trajectory transfer, this dissertation theoretically studies the application and optimization methods of finite thrust trajectory transfer. The main contents are as follows:In the aspect of basic theory: the development of finite thrust space exploration missions all over the world are tracked; The research actualities of the three kinds of finite thrust trajectory transfer optimization algorithms are introduced as well as the corresponding advantages and disadvantages; The trajectory dynamic models described by different coordinate frames, the normalization skill to the models and the ephemeris information are fully expatiated; The fundamentals and methods of ordinal optimization(OO) theory and genetic algorithm(GA) are discussed systematically; The transformation of the objectives and the constraint conditions in the multi-objective optimization problem are presented.In the aspect of the improvement and implementation of optimization algorithm: In order to solve the problem of large ranges of optimized parameters in the direct method, a parameter selection algorithm based on OO theory is presented and two classical test functions are picked up to validate the feasibility of the algorithm; The performance of the algorithm is evaluated through an important multi-objective optimization problem. The results show that, for complicated multi-objective multi-constraint problems, the algorithm is capable of reducing the search ranges of the parameters and leading to a better convergence. In order to solve the problem of huge computational loads existed in the multi-objective optimization problem along with taking full advantages of the inner parallel property of the GA, an universal distributed parallel computational system based on the server/client pattern is established. In this computational system the optimization algorithm is the server and some computational clients compute the procedures which have huge computational loads.In the aspect of applications of the optimization method: the optimal trajectory transfer at the apogee of GEO satellite and the optimization of Earth-Mars finite thrust trajectory transfer are solved. After setting up the trajectory dynamic models in appropriate coordinate frames, a parametrization method is used to determine the optimized control variables and then the trajectory control optimization model is established; The problem is transformed into a single-objective optimization problem using the methods of weighting and penalty factors; The ranges of the optimized parameters are selected through the methods of contour and parameter selection algorithm based on OO theory; Two optimal projects are simulated using multi-objective GA based on OO theory and the simulation results illustrate the comparative analyses between using the parameter selection algorithm before and after. The results demonstrate that this method is fitted for all kinds of problems and is capable of improving the efficiency of direct optimization algorithm dramatically.The research achievements possess favorably applicable foreground in the field of finite thrust trajectory optimization which can provide some technical and theoretical references for our future space exploration missions.