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

, 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 or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

from Earth, around the far side of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

, and back to Earth using only

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

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 ( rus, Луна 3}) 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 th ...

. Circumlunar trajectories were also used by

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label= Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label ...

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 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 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 or Zond programme, and several US proposals, including

Gemini Gemini may refer to: Space * Gemini (constellation), one of the constellations of the zodiac ** Gemini in Chinese astronomy * Project Gemini, the second U.S. crewed spaceflight program * Gemini Observatory, consisting of telescopes in the Norther ...

- Centaur and an early Apollo proposal. The latest circumlunar mission was 2022 NASA Artemis 1.

Planned

The ''dearMoon'' project is planned as a 2023 circumlunar flight using the

SpaceX Starship Starship is a fully reusable, super heavy-lift launch vehicle under development by SpaceX, an American aerospace company. With more than twice the thrust of the Saturn V, it is designed to be the most powerful launch vehicle ever built and the ...

to carry approximately 10 tourists on a multiday flight to the Moon and back.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 {{space-stub

History

Planned

See also

References