Launch opportunity research for Earth-Mars low thrust trajectory

Low thrust trajectory design and optimization is a challengeable work in interplanetary exploration. The launch opportunity of low thrust trajectory is studied in the paper. Based on a hybrid method, the low thrust optimal control problem is converted to a parameters optimization problem. An adjoint control transformation is proposed for decreasing the difficulty of initial values guess. And the solution searching scope can be reduced effectively through the introduction of adjoint control transformation, which converts costate state to other variables which possess actual range and meaning partially. Finally, a global-local searching procedure is proposed for obtaining the low thrust trajectory launch opportunities. Differential evolution algorithm is used to generate initial values for the nonlinear programming problem, and sequential quadratic programming algorithm is used for improving the accurate of solutions. The effectiveness of proposed method is validated through three Earth-Mars missions low thrust trajectory design.