Abstract: Minimumtime orbit transfers for solar sail spacecraft base on genetic algorithm (GA) are explored.The optimal control law is derived from the maximum principle, minimum time consumption is chosen as the optimization objective, and the launch date, the arrive date and the initial guess of the costates are optimized by using GA. In order to deal with the design of transfer orbit with many constraints，the penalty function is introduced into the GA.Orbit transfers for solar sail from Earth’s synchronous heliocentric orbit to Mars’ synchronous heliocentric orbit and from Earth to Mars have been designed and simulated as examples. Results of simulation show correctness and practicability of proposed orbit transfer algorithm.

Key words: solar sail, global optimization, genetic algorithm(GA), transfer orbit, penalty function