John Cornelius Houbolt was an aerospace engineer credited with leading the team behind the lunar orbit rendezvous (LOR) mission mode, a concept that was used to successfully land humans on the Moon and return them to Earth. This flight path was chosen for the Apollo program in July 1962. The critical decision to use LOR was viewed as vital to ensuring that man reached the Moon by the end of the decade as proposed by President John F. Kennedy. In the process, LOR saved time and billions of dollars by efficiently using the rocket and spacecraft technologies.

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 smaller 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.