Lunar orbit rendezvous (LOR) is a process for landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a lunar lander travel to lunar orbit. The lunar lander then independently descends to the surface of the Moon, while the main spacecraft remains in lunar orbit. After completion of the mission there, the lander returns to lunar orbit to rendezvous and re-dock with the main spacecraft, then is discarded after transfer of crew and payload. Only the main spacecraft returns to Earth.
Lunar orbit rendezvous was first proposed in 1919 by Ukrainian engineer Yuri Kondratyuk, as the most economical way of sending a human on a round-trip journey to the Moon.
At the beginning of the Apollo program, Kraft retired as a flight director to concentrate on management and mission planning. In 1972, he became director of the Manned Spacecraft Center (later Johnson Space Center), following in the footsteps of his mentor Robert R. Gilruth. He held the position until his 1982 retirement from NASA. During his retirement, Kraft has consulted for numerous companies including IBM and Rockwell International, and he published an autobiography entitled Flight: My Life in Mission Control.
More than any other person, Kraft was responsible for shaping the organization and culture of NASA's Mission Control. As his protégé Glynn Lunney commented, "the Control Center today ... is a reflection of Chris Kraft." When Kraft received the National Space Trophy from the Rotary Club in 1999, the organization described him as "a driving force in the U.S. human space flight program from its beginnings to the Space Shuttle era, a man whose accomplishments have become legendary."