space rocket vs rocket engine

space rocket and rocket engine both are nouns.

Word	Noun	Adjective	Verb	Adverb
space rocket	Yes	No	No	No
rocket engine	Yes	No	No	No

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

space rocket: a rocket powerful enough to travel into outer space
rocket engine: a jet engine containing its own propellant and driven by reaction propulsion

Other hypernyms of space rocket include rocket.

space rocket (noun)	rocket engine (noun)
a rocket powerful enough to travel into outer space	a jet engine containing its own propellant and driven by reaction propulsion