Low energy trajectories for the Moon-to-Earth space flight
The Moon-to-Earth low energy trajectories of ‘detour’ type are found and studied within the frame of the Moon-Earth-Sun-particle system. These trajectories use a passive flight to the Earth from an initial elliptic selenocentric orbit with a high aposelenium. The Earth perturbation increases the particle selenocentric energy from a negative value first to zero and then to a positive one and therefore leads to a passive escape of the particle motion from the Moon attraction near the translunar libration pointL2. This results in the particle flight to a distance of about 1.5 million km from the Earth where the Sun gravitation decreases the particle orbit perigee distance to a small value that leads to the particle approaching the Earth vicinity in about 100 days of the flight. A set of the Moon-to-Earth ‘detour’ trajectories is defined numerically. Characteristics of these trajectories are presented. The ‘detour’ trajectories give essential economy of energy (about 150 m/s in Delta V) relative to the usual ones.