One of the biggest problems NASA faced when planning the Apollo 11 mission to the moon wasn’t in fact getting the men on the moon, rather, getting them safely back home. After constant failure, an idea finally came through; Lunar Orbit Rendezvous or LOR.  The idea was proposed by Dr. John Houbolt in 1961, but was quickly shot down because of how risky the procedure was. Houbolt never gave up and fiercely fought to keep the argument for LOR alive. Houbolt’s relentlessness finally paid off and in 1962 NASA confirmed that they would be using LOR for the mission. In a LOR mission a main spacecraft and a smaller lunar module travel together into lunar orbit. The lunar module then independently descends to the lunar surface. After completion of the mission there, a part of it returns to lunar orbit and conducts a rendezvous with the main spacecraft. The main spacecraft then returns back to Earth. The idea seems simple enough, but the rendezvous has to be precise or the consequences could be fatal. The two worst possible outcomes are as followed: 1) if the rendezvous in lunar orbit failed, the lunar module astronauts would be stranded and could not return to Earth, 2) if the Service Module engine failed after the rendezvous in lunar orbit, no astronauts would return. One advantage of lunar orbit rendezvous is that the propellant necessary to return from lunar orbit back to the Earth need not be carried down to the Moon, and back up from the Moon again. This saves the propellant needed to move that propellant, which is considerable; it also reduces tank weight and greatly reduces the sizes of the engines for the lunar lander. Disadvantages include the lunar lander needing a separate life-support system and requiring two sets of engines, one on the lunar lander and another attached to the command module.