step rocket vs takeoff rocket

step rocket and takeoff rocket both are nouns.

Word	Noun	Adjective	Verb	Adverb
step rocket	Yes	No	No	No
takeoff rocket	Yes	No	No	No

step rocket (noun)	takeoff rocket (noun)
a rocket having two or more rocket engines (each with its own fuel) that are fired in succession and jettisoned when the fuel is exhausted	the first stage of a multistage rocket