The first is Direct takeoff 。 As the name implies, a huge rocket (named "Nova") takes off directly and carries all spacecraft required for landing on the moon to the moon alone. The second is the Earth orbit assembly. Two smaller rockets carry spacecraft and fuel to dock in Earth orbit, and then go to the moon.
The third is the lunar orbit assembly, a proposal proposed by John C. Hobart's team. In this scheme, a large spacecraft carries a moon landing spacecraft carrying astronauts. After entering the lunar orbit, the moon landing spacecraft is separated from the main spacecraft and landed on the moon surface; The main spacecraft remained in lunar orbit. One of the three astronauts remained in the main spacecraft. After the moon landing is completed, the moon landing spacecraft takes off again, gathers with the main spacecraft in lunar orbit, and returns to the earth.
