Continuous low thrust trajectory optimization for preliminary design

Mission design using continuous low thrust propulsion is an interesting but challenging task. In this paper, a virtual central gravitational field method is proposed for continuous low thrust trajectory design in preliminary stage. The basic idea of presented method is to form a virtual gravity using continuous thrust, in which the spacecraft flies in a virtual conic orbit to accomplish trajectory maneuver. Therefore, the continuous thrust non-Keplerian trajectory can be parameterized, and solved analytically. Instead of providing some special initial guesses for the more accurate optimizer, a large number of feasible initial guesses can be located quickly using the proposed method. Three examples are presented as the applications of the proposed technique to test its suitability, including the Earth to Mars rendezvous mission; the Earth–Mars–Ceres rendezvous mission; and a near-Earth collision-speed maximal interception mission. In order to verify the efficiency of the proposed method, the solutions generated by the shape-based method are used to compare. It shows that the virtual central gravitational field method can parameterize a large number of non-Keplerian orbits using parameters of virtual gravity, and provide initial guess for more accurate optimizer. Compared with the shape-based method, it requires more fuel cost using the proposed method in rendezvous trajectory design, especially in long flight time case. However, there is no constraint about the direction of thrust, so it is simple and flexible to change the velocity and position. The capability of rapid maneuver in short flight time outperforms the shape-based method discussed in prior papers, and it can be applied to providing initial guesses for continuous thrust rapid maneuver trajectory mission design in preliminary stage.