There may be differences between the US and UK, but if we're working from the same rules, it should be NASA. It is not a word like laser or scuba, it is the proper name of an organization, like NATO.

Bob, Wichita KS, USA

That's the difference between an acronym and a mere abbreviation. An acronym is an abbreviation that can be said as a word.

Marty, Melbourne, AU

"An acronym doesn't need to be in capitals if it can be said as a word." Actually, that is the definition of "acronym". Otherwise, it's an initialism (like U.S.A.). "U.N. " is correct and "scuba" is correct. Only the latter is an acronym.

Jay, Toronto, Canada

Nope, it's Nasa. An acronym doesn't need to be in capitals if it can be said as a word.

Dave, London, UK

Must have missed the lesson where I was advised that a vacum had no air but a detectable aroma." Outer space" at a few molucules per square kilometre would need one hell of a nose.

robert everitt, wolverhampton,

It's NASA not Nasa

Keith, Wayne NJ, USA