NASA, Project Apollo, Apollo program, space program, lunar landing, moon landing, moon program, lunar module, command module, moonwalk, EVA, spacewalk, rendezvous, lunar orbit, earth orbit, orbit, reentry, weightlessness, 1/6 g, Apollo 7, Apollo 8, Apollo 9, Apollo 10, Apollo 11, Apollo 12, Apollo 13, Apollo 14, Apollo 15, Apollo 16, Apollo 17