straightaway vs right away

straightaway is a noun but right away is not a noun.

Word	Noun	Adjective	Verb	Adverb
straightaway	Yes	Yes	No	Yes
right away	No	No	No	Yes

As adverbs, straightaway and right away are synonyms defined as:

straightaway and right away: without delay or hesitation; with no time intervening

Other synonyms of straightaway include at once, directly, forthwith, immediately, instantly, like a shot, now, straight off.

straightaway (noun)	right away (noun)
a straight segment of a roadway or racecourse

straightaway (adjective)	right away (adjective)
performed with little or no delay

straightaway (adverb)	right away (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
	at once (usually modifies an undesirable occurrence)