Let me preface this question with a disclaimer: I’m an idiot.
That being said… If a woman were to go into space, would there a need for her to wear a bra? My guess is no, because no gravity means no boob sagging.
Am I right or am I totally out of whack?
Rrrowr!
My guess is that a bra would be even more necessary. Something like a sports bra. Just to keep the fun bags located.
A bra would be good to stop things floating and wobbling around, but it should be engineered quite differently. Just because the boobs are upwards, doesn’t mean jiggling/movement wouldn’t be uncomfortable or painful. Eg: in the sea, boobs float, but they’re not “controlled” - not up and standing tall like silicone ones, they bob around a bit.
Now of course that’s got me wondering about men’s parts on the moon… 
You posted this same thread yesterday. If you don’t check your thread for a day or two, it could easily be two or three pages down. You should ask a mod to close this one.