The APOLLO lunar module, or LM, was the first true spacecraft - designed to fly only in a vacuum, with no aerodynamic qualities whatsoever. Launched attached to the APOLLO command/service module, it separated in lunar orbit and descended to the Moon with two astronauts inside. At the end of their stay on the surface, the lunar module's ascent stage fired its own rocket to rejoin the command/service module in lunar orbit.

APOLLO 9 (March 3-13, 1969) was the first space test of the third critical piece of APOLLO hardware - the lunar module. For ten days, the astronauts put all three APOLLO vehicles through their paces in Earth Orbit, undocking and then redocking the lunar lander with the command module, just as they would in lunar orbit. For this and all subsequent APOLLO flights, the crew were allowed to name their own spacecraft. The gangly lunar module was "Spider," the command module "Gumdrop." (names selected for APOLLO 9)

(The above narrative is from SPACE FLIGHT THE FIRST 30 YEARS, NASA publication NP-150, December 1991, p. 12 and 14.)