A circumlunar trajectory, trans-lunar trajectory or lunar free return
is a type of free return trajectory which takes a spacecraft from
Earth, around the far side of the Moon, and back to Earth using only
gravity once the initial trajectory is set.
The first spacecraft to fly a circumlunar trajectory was Luna 3.
Circumlunar trajectories were also used by Apollo missions prior to
lunar orbit insertion, to provide a free return to Earth in the
event of a propulsion system malfunction on the way to the Moon. This
was used on Apollo 13, when an oxygen tank rupture necessitated return
to Earth without firing the Service Module engine, although a number
of course corrections using the Lunar Module descent engine were
required to maintain this trajectory.
A number of manned missions were also proposed to intentionally
conduct circumlunar flybys, including the Soviet
Free return trajectory Trans-lunar injection
^ "The launch and mission trajectory".
This space- or spaceflight-related article is a stub. You can help by expandi