HOWSTUFFWORKS: How the Apollo Spacecraft Worked
The quickest and dirtiest way to get to the moon was with one big rocket. Send it to land on the moon, relaunch, and come home. It would look just like it did on TV. But there were other, less obvious ways like storing a fuel depot in Earth orbit for a spacecraft to refuel on route.
In 1959, Langley engineer William H. Michael proposed such a method with the promise that it would simplify the launch. The proposal did more than just answer the question about to get to the moon, it highlighted the inevitable necessity of knowing how to rendezvous in orbit.
Thomas Dolan, an engineer from Chance-Vought, added another opinion to the lunar mission puzzle. He took the same mission as Michael but added a modular spacecraft that could be discarded with every stage to cut costs even further. Steadily, some mission involving rendezvous was emerging as a favorite.
In 1960, Langley engineer John C. Houbolt, who chaired a special committee for rendezvous study at Langley and gave the Mercury astronauts' lectures on space navigation, had an epiphany about orbital rendezvous. It was, he realized, the only way to send a large spacecraft to the moon. It would cut launch costs in half and could be done faster since it didn't require development of huge rockets. He was so convinced of this that resolved to work hard convincing NASA higher ups that rendezvous was an inevitable part of the agency's future endeavors.