space travel vs voyage

space travel and voyage both are nouns.

Word	Noun	Adjective	Verb	Adverb
space travel	Yes	No	No	No
voyage	Yes	No	Yes	No

As nouns, voyage is a hypernym of space travel; that is, voyage is a word with a broader meaning than space travel:

space travel (noun)	voyage (noun)
a voyage outside the Earth's atmosphere	a journey to some distant place
	an act of traveling by water

space travel (verb)	voyage (verb)
	travel on water propelled by wind or by other means