Want to stay on top of all the space news? Follow @universetoday on TwitterThe Apollo space program was conceived early in 1960 as a follow-up to the Mercury program. While the Mercury capsule could only support one astronaut on a limited Earth orbital mission, the Apollo spacecraft was to be able to carry three astronauts on a circumlunar flight and perhaps even on a lunar landing. While NASA went ahead with planning for Apollo, funding for the program was far from certain. In November 1960, President-elect John F. Kennedy promised American superiority over the in the fields of space exploration and missile defense. Using space exploration as a symbol of national prestige, he warned of a missile gap between the two nations, pledging to make the U.S. not “first but, first and, first if, but first period.” He knew little about the technical details of the space program, and was put off by the massive financial commitment required by a manned moon landing.
Once it was decided that NASA was to go to the Moon, the decision had to be made as to how to approach a landing. There were four possible options: direct ascent, Earth orbit rendezvous, lunar surface rendezvous, lunar orbit rendezvous. Each had its points and detractions. Finally, the decision was made to go with a lunar orbit rendezvous(LOR). In this method one Saturn V would launch a spacecraft that was composed of modular parts. The command module would remain in orbit around the moon, while the lunar module would descend to the Moon and then return to dock with the command ship while still in lunar orbit. In contrast with the other plans, LOR required only a small part of the spacecraft to land on the Moon, thereby minimizing the mass to be launched from the Moon’s surface for the return trip.
There were 20 Apollo missions planned, but the last three(18-20) were canceled because of budget shortfalls. There were to be seven different mission types–lettered A through G– , two more types were added later(H and J). A and B were unmanned tests of the CSM and LM. C and D put the CSM and LM in remain in low Earth orbit separately, then together. E missions put the CSM/LM combo into elliptical orbit around the Earth. F put the pair into lunar orbit. G missions were for short term lunar landings. H missions put people on the Moon for 2 days and included EVA’s. J missions left astronauts on the surface for three days and included more experiments and EVA’s.
Well, there you have a brief overview of the Apollo space program. There is a much more indepth article about Apollo, here. We have a great article about the program here on Universe Today. Astronomy Cast offers a good episode about Moon exploration.