The Alternatives Considered to Get to the Moon
A rocket would be launched directly to the moon. After landing on the lunar surface, it would be launched back to Earth, leaving its landing stage on the moon.
EOR (Earth Orbit Rendezvous)
Up to 15 rockets (depending on the plan) would be launched carrying different parts of a spacecraft, which would be assembled in the orbit of the Earth. Once completed, the spacecraft would leave the earth orbit to get to the moon and land there. It would return to Earth the same way as the direct ascent alternative would.
LOR (Lunar Orbit Rendezvous)
A spacecraft would be launched to orbit the moon. Then, a smaller spacecraft would be detached from it and land on the moon while the other keeps orbiting around the moon. The one that gets to the surface of the moon would leave its landing stage and be launched back to the lunar orbit where it would dock with the orbiting spacecraft to transfer the crew and then be discarded.
Lunar Surface Rendezvous
An unmanned spacecraft would be launched to the moon, followed by a second spacecraft that would carry the mission crew. Both would land on the moon. The first one, an automated spacecraft, would be carrying propellant to refuel the crewed spacecraft on the moon, so that it can be launched back to earth.
By Matías Lago