Double Flybys of a Planet in Space Missions

Interplanetary flights are considered in which a spacecraft performs two successive flybys of a single planet. The trajectory of the spacecraft before and after such a double gravity assist maneuver is considered given. It is also assumed that, between flybys of the planet, the spacecraft moves along a passive trajectory and that during the flybys active maneuvers are possible. The requirements that the trajectory between flybys must satisfy are determined. In cases in which such a trajectory is not the only one, a method for its optimization (i.e., minimization of the total impulse) is indicated.