abstract:Earth orbit rendezvous (EOR) is a potential methodology for conducting round trip human flights to the Moon, involving the use of space rendezvous to assemble, and possibly fuel, components of a translunar vehicle in low Earth orbit."LOW EARTH ORBIT RENDEZVOUS STRATEGY FOR LUNAR MISSIONS" http://www.
For example, instead of the lunar rendezvous method that NASA chose for the Apollo program, the player can opt for Earth-orbit rendezvous or even direct-ascent where a single giant spacecraft lifts off from Earth and lands on the Moon.