Transposition, docking, and extraction (often abbreviated to transposition and docking) was a maneuver performed during

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= ...

lunar landing A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both crewed and robotic missions. The first human-made object to touch the Moon was the Soviet Union's Luna 2, on 13 September 1959. The United S ...

missions from 1969 to 1972, to withdraw the

Apollo 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 ...

(LM) from its adapter housing which secured it to the

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and sys ...

upper stage and protected it from the aerodynamic stresses of launch. The maneuver involved the command module pilot separating the

Apollo Command and Service Module The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother sh ...

(CSM) from the adapter, turning the CSM around, and docking its nose to the Lunar Module, then pulling the combined spacecraft away from the upper stage. It was performed shortly after the

trans-lunar injection A trans-lunar injection (TLI) is a propulsive maneuver used to set a spacecraft on a trajectory that will cause it to arrive at the Moon. History The first space probe to attempt TLI was the Soviet Union's Luna 1 on January 2, 1959 which w ...

maneuver that placed the

Apollo spacecraft The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft ...

on a three-day trajectory to 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 ...

. The docking created a continuous, pressurized tunnel which permitted the astronauts to transfer internally between the CSM and the LM. The same maneuver was performed on the 1975

Apollo–Soyuz Test Project Apollo–Soyuz was the first crewed international space mission, carried out jointly by the United States and the Soviet Union in July 1975. Millions of people around the world watched on television as a United States Apollo spacecraft docked ...

(ASTP) mission to extract a special docking module used to connect the Apollo Command Module with the

Soyuz spacecraft Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecr ...

Procedure

Transposition and docking was performed by the Command Module Pilot (CMP) (although, as a backup, the Commander and Lunar Module Pilot (or ASTP Docking Module Pilot) were also trained to perform the maneuver), and involved the following steps: #A "CSM/LV Sep" button on the control panel was pressed, which ignited detonating cord and separated the CSM from the Spacecraft–lunar module adapter (SLA), and the four adapter panels from each other and the S-IVB upper stage. This exposed the LM. #The CSM's

translation Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

thrusters were used to move it a safe distance away.

Rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

thrusters were then used to pitch up the CSM 180° and roll it to the proper alignment angle for docking. Translation thrusters were then used to move it back to the LM. A T-shaped docking target on the top of the LM aligned optically with a reticle pattern on the CMP's left-hand docking window to ensure proper spacecraft alignment. #A soft dock was achieved when a probe at the top of the CSM was inserted into a hole in the center of a cone-shaped drogue at the top of the LM and three small capture latches closed. Hard dock was achieved by activating a mechanism which retracted the probe and caused twelve more capture latches to close around the command module's docking flange. #A pressure equalization valve in the CM forward hatch was opened to allow oxygen to fill the LM through a similar valve in its hatch that was left open at launch. When the pressure equalized, the pilot removed the CM hatch, removed the probe and drogue, inspected the capture latches, and connected two

umbilical cable An umbilical cable or umbilical is a cable and/or hose that supplies required consumables to an apparatus, like a rocket, or to a person, such as a diver or astronaut. It is named by analogy with an umbilical cord. An umbilical can, for example, ...

s which electrically connected the CM and LM. He then replaced the CM hatch. #The LM hold-down attachments and umbilical connection to the S-IVB Instrument Unit were released, and the CSM's translation thrusters were used to pull the CSM/LM stack a safe distance away from the S-IVB, which would then be steered by ground control either to a

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...

, or to a deliberate crash landing on the Moon. The astronauts were in no hurry to complete this maneuver, which nominally took about an hour. It would take longer if problems were encountered; for instance, Stuart Roosa had trouble getting the capture latches to engage for docking on

Apollo 14 Apollo 14 (January 31, 1971February 9, 1971) was the eighth crewed mission in the United States Apollo program, the third to land on the Moon, and the first to land in the lunar highlands. It was the last of the " H missions", landings at ...

, and the procedure took two hours and eighteen minutes.

Missions

Transposition and docking was performed on all Apollo missions which carried both the CSM and the LM, from

Apollo 9 Apollo 9 (March 313, 1969) was the third human spaceflight in NASA's Apollo program. Flown in low Earth orbit, it was the second crewed Apollo mission that the United States launched via a Saturn V rocket, and was the first flight of the ful ...

onward. Transposition and a mock LM-docking approach was first simulated on the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

-orbiting

Apollo 7 Apollo 7 (October 1122, 1968) was the first crewed flight in NASA's Apollo program, and saw the resumption of human spaceflight by the agency after the fire that killed the three Apollo 1 astronauts during a launch rehearsal test on Ja ...

flight (which carried a docking target in the SLA, but no LM). The "Block I" SLA used on the early

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43 ...

launch vehicles had panels that opened at a 45° angle but did not separate from the S‑IVB. One of the panels did not open the full angle, preventing the crew from approaching the S‑IVB for fear they might strike this panel. This was corrected with the "Block II" SLA design used on all crewed

Apollo flights (starting with

Apollo 8 Apollo 8 (December 21–27, 1968) was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon. The crew orbited the Moon ten times without landing, and then departed safely back to Earth. The ...

), which detached the panels and pushed them away from the S‑IVB with springs. The last mission to use the maneuver was the

mission, in which the Apollo CSM docked to a specially designed adapter module which carried docking equipment compatible with the Soyuz 19 spacecraft.

References

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External links

Apollo 15 Flight Journal: Transposition, Docking and Extraction
Astrodynamics Orbital maneuvers Apollo program Articles containing video clips

Procedure

Missions

See also

References

External links