Sentence:  Several initial experimental firings of the various stages of Saturn V into earth orbit will precede the planned <WSD>lunar</WSD> flight. The astronauts will practice rendezvous techniques in the earth's orbit. [...] Before they reach the moon the astronauts will have another difficult maneuver to perform—turning their command module around so that its nose is attached to the top of the <WSD>lunar</WSD> excursion module. Two of the crew members will transfer from the command module to the <WSD>lunar</WSD> excursion module. 
Meaning of the word marked with <WSD> tags:  Of or pertaining to travel through space between the Earth and the Moon, or exploration and scientific investigation of the Moon.