rapid growth vs ascension

rapid growth and ascension both are nouns.

Word	Noun	Adjective	Verb	Adverb
rapid growth	Yes	No	No	No
ascension	Yes	No	No	No

As nouns, ascension is a hypernym of rapid growth; that is, ascension is a word with a broader meaning than rapid growth:

Other hypernyms of rapid growth include ascent, rise, rising.

rapid growth (noun)	ascension (noun)
a rapid rise	the act of changing location in an upward direction
	a movement upward; rise above the ground
	(astronomy) the rising of a star above the horizon