Transposition, docking, and extraction

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Transposition, docking, and extraction (abbreviated to TD&E, often just transposition and docking) was a space rendezvous maneuver performed during the Apollo lunar missions of the 1960s and 70s. It was performed after the trans lunar injection burn that placed the Apollo spacecraft on the trajectory towards the Moon, but before reaching the Moon or attaining lunar orbit.

Performing TD&E[edit]

It was performed by the Command Module pilot (although, as a contingency, the Lunar Module pilot and commander were also trained to perform the maneuver), and involved separating the CSM from the S-IVB, pitching the CSM 180° and proceeding to dock with the Lunar Module, by inserting a probe at the top the CSM into a drogue at the top of the Lunar Module. Then, the Apollo spacecraft stack would separate from the S-IVB, which would then either continue on to a heliocentric orbit or be deliberately steered into a crash landing on the Moon.

Missions[edit]

TD&E on Apollo 15, performed by Al Worden

TD&E was performed on all Apollo missions from Apollo 9 onward, as these flights carried the LM. The maneuver was first practiced on the Earth-orbiting Apollo 7 flight, but the S‑IVB utilized a LM fairing adapter that did not separate from the S‑IVB, so the crew could not approach the S‑IVB in fear that the adapter "petals" would strike the Apollo CSM. This was corrected with all flights commencing with Apollo 8 when the fairing "petals" would fall away from the S‑IVB.[1]

The last mission to use the TD&E maneuver was the Apollo-Soyuz Test Project mission in which the Apollo CSM used the procedure to extract the docking adapter used to link up the Apollo and Soyuz 19 spacecraft in the first and only joint mission between the USA and the Soviet Union (although there would be much future cooperation in space between the post-Soviet Roskosmos and NASA).

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