ADOPT A METHOD

To pursue President Kennedy’s challenge, NASA defined three methods of achieving a lunar landing and safe return: (1) direct ascent from the surface of the Earth to the surface of the Moon; (2) rendezvous of all of the mission elements in Earth orbit and then proceed directly to the lunar surface (EOR); and (3) fly into lunar orbit and send down a specialised lander while the mothership remained in space, then rendezvous upon lifting off from the Moon (LOR). In June 1962 it was decided to use LOR. Thus "rendezvous" became the key to the method. Actually, at that lime LOR was seen as the most hazardous option – we had not yet attempted a rendezvous of any type, even in Earth orbit (the first would not be for another 3 Vi years), much less around the Moon, 240,000 miles away, where, on the far side, there was no ground tracking nor any contact with the engineers in the Mission Control Center. But LOR drove the design of the entire lunar landing ‘‘system" – spacecraft (hardware and software); ground facilities, and in particular the resulting complex flight operations, techniques, and procedures.

To illustrate the necessary complexity of this method, ten distinct phases of a lunar surface mission were defined, each operating in a different domain: (1) launch from Earth; (2) Earth orbit; (3) translunar (and later trans-Earth); (4) entry into lunar orbit (and later departure from lunar orbit); (5) operations in lunar orbit; (6) descent to the surface and landing; (7) surface operations; (8) lunar ascent. (9) lunar rendezvous; and (10) Earth re-entry.