a tunnel between the nose of the Command Module and the roof of the Lunar Module. These maneuvers were first demonstrated in low Earth orbit on March 7, 1969, on Apollo 9, then in lunar orbit in May 1969 on Apollo 10, then in six lunar landing missions, as well as on Apollo 13 where the LM was used as a rescue vehicle instead of making a lunar landing.

Unlike the United States, which used manual