Improved direct-shooting method for low-thrust trajectories optimization

For low-thrust trajectories optimization, an improved direct-shooting method is proposed to overcome the two major drawbacks of the original one: the low-thrust trajectories are computed inefficiently using explicit numerical integration; and the control steering profile is more likely to converge at local optimum due to its local linear interpolation characteristics. The measures taken in this work include deducing an analytical solution of the low-thrust trajectory and representing the low-thrust control as a global fourth-order polynomial. The proposed method has been tested on two rendezvous missions: one from the Earth to Mars, the other to near-Earth asteroid 2001GP2.