orbital mechanics Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to rockets, satellites, and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and the law of universal ...

, a circumlunar trajectory, trans-lunar trajectory or lunar free return is a type of

free return trajectory In orbital mechanics, a free-return trajectory is a trajectory of a spacecraft traveling away from a primary body (for example, the Earth) where gravity due to a secondary body (for example, the Moon) causes the spacecraft to return to the primar ...

which takes a

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

from Earth, around the far side of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

, and back to Earth using only

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

once the initial trajectory is set.

History

The first spacecraft to fly a circumlunar trajectory was

Luna 3 Luna 3, or E-2A No.1 (), was a Soviet spacecraft launched in 1959 as part of the Luna programme. It was the first mission to photograph the far side of the Moon and the third Soviet space probe to be sent to the neighborhood of the Moon. The hi ...

. Circumlunar trajectories were also used by

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

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 Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo program, Apollo space program and would have been the third Moon landing. The craft was launched from Kennedy Space Center on April 11, 1970, but the landing was abort ...

, when an oxygen tank rupture necessitated return to Earth without firing the

Service Module A service module (also known as an equipment module or instrument compartment) is a component of a crewed space capsule containing a variety of support systems used for spacecraft operations. Usually located in the uninhabited area of the spacec ...

engine, although a number of course corrections using the

Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed s ...

descent engine were used to refine the trajectory. A number of proposed, but not flown, crewed missions have been planned to intentionally conduct circumlunar flybys, including the Soviet

Soyuz 7K-L1 Soyuz 7K-L1 "Zond" spacecraft was designed to launch cosmonaut, cosmonauts from the Earth to circle the Moon without going into lunar orbit in the context of the Soviet crewed lunar programs, Soviet crewed Moon-flyby program in the Moon race. ...

or Zond programme, and several US proposals, including Gemini-

Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

and an early Apollo proposal. The latest circumlunar mission was 2022 NASA

Artemis 1 Artemis I, formerly Exploration Mission-1 (EM-1), was an uncrewed Moon-orbiting mission that was launched in November 2022. As the first major spaceflight of NASA's Artemis program, Artemis I marked the agency's return to lunar exploration a ...

. How SpaceX's 1st Passenger Flight Around the Moon with Yusaku Maezawa Will Work
. Tariq Malik, ''Space.com'', 18 September 2018, accessed 25 August 2019.

References

Exploration of the Moon Orbits {{space-stub

History

See also

References