Study On Trajectory Optimization Design Method For Multi-target Deep Space Exploration

One flight mission with multiple exploration targets is the important development idea and manner for future deep space exploration missions and the trajectory design optimization is one key problem for deep space exploration technologies. With the background of the multi-target deep space exploration missions, the optimization of impulsive and low-thrust trajectories, the optimization of sequence exploration missions with gravity assistant maneuvers, and the multi-objective optimization of multi-asteroid rendezvous are studied. The main results achieved in this dissertation are summarized as follows.The impulsive trajectory optimization method for deep space exploration mission is developed. The constraints regarding of the realization of low-thrust propulsion is incorporated into the impulsive trajectory design, and a corresponding optimization method with considering this constraint is proposed. The integrated model of designing the launch window and multi-impulsive transfer trajectory is built, and an optimization method using the multi-objective evolutionary algorithm is proposed. The method can effectively reveal the relationships characteristics among the overall mission parameters and can provide good references for the design of practical missions.Two simple and effective methods for deep space low-trust trajectory optimization are proposed. A direct low-thrust rendezvous optimization method is proposed by combining a continuous-thrust model in orthogonal coordinate and a fixed-thrust model in spherical coordinate. The comparisons with optimal results of pseudospectral methods validate the global optimization ability and efficiency of the proposed approach. A hybrid global optimization approach for fuel-optimal low-trust rendezvous two-point boundary value problem is proposed by combining the ideas of the homotopic method and the advantages of different optimization algorithms. The optimal bang-bang trust history can be reliably obtained by this approach.The trajectory optimization approach of sequence exploration missions with gravity assist maneuvers is developed. The deep space multi-impulse rendezvous optimization model using gravity assist maneuvers of planet is established. The problem of choosing optimization design variables of exploring asteroids between visiting planets is discussed, and an optimization method using a differential evolution algorithm is provided. With the background of the problem in the third national deep space trajectory optimization competition, an optimization approach for a classic sequence exploration mission with gravity assist maneuvers is proposed, and the approach can effectively determine the sub-optimal exploration targets and the corresponding flight sequence from lots of potential targets.A multi-objective optimization approach for deep space multi-asteroid rendezvous is proposed. The multi-objective two-level mixed integer nonlinear programming model for multi-asteroid rendezvous is built, and an optimization approach combining a mix-coded genetic algorithm using the fast-nondominated sorting algorithm and the multi-revolution Lambert algorithm is proposed. The proposed approach is testified by solving an 18-asteriod rendezvous problem and the characteristic of multi-asteroid rendezvous is demonstrated by comparing the fronts between the fuel-optimal solutions and fuel-time multi-objective Pareto solutions.The impulsive and low-thrust trajectory optimization methods for deep space missions are beneficially improved, and the mission optimization approaches for sequence exploration missions with gravity assist maenuvers and for multiple-asteriod rendezvous are proposed. The achievements provide several effective new ideas and optimization techniques for trajectory design of a multi-target deep space exploration mission.