test rocket vs test instrument vehicle

test rocket and test instrument vehicle both are nouns.

Word	Noun	Adjective	Verb	Adverb
test rocket	Yes	No	No	No
test instrument vehicle	Yes	No	No	No

As nouns, test rocket and test instrument vehicle are synonyms defined as:

test rocket and test instrument vehicle: a rocket fired for test purposes

Other synonyms of test rocket include research rocket.

test rocket (noun)	test instrument vehicle (noun)
a rocket fired for test purposes	a rocket fired for test purposes