1st ACT global trajectory optimisation competition: Results found at the Jet Propulsion Laboratory

Results obtained at the Jet Propulsion Laboratory for the 1st ACT global trajectory optimisation competition are presented and the methods used to obtain them are described. The search for the globally optimal, low-thrust, gravity-assist trajectory for maximally deflecting an asteroid is performed in two steps. The first step involves a rough global search of the global search space, which has, however, been somewhat bounded based on prior mission-design experience, intuition, and energy arguments. A shape-based method is used to represent the low-thrust arcs, while the ballistic portions are searched almost exhaustively. The second step involves local optimisation of trajectories which stand out from the rough global search. The low-thrust optimisation problem is turned into a parameter optimisation problem by approximating the continuous thrusting as a series of impulsive manoeuvres. Of the many trajectories found, three optimal trajectories are reported and compared, including the one submitted for the competition. The best one employed a double-Venus, quadruple-Earth, Jupiter–Saturn–Jupiter gravity-assist sequence. The trajectory submitted for the competition used one less Venus flyby and one less Earth flyby.