Than hell yes.  I think sex in zero G would be a blast!

Think of what it would be like to make a squirter cum in Zero G!  The images are endless.  
Perhaps the next frontier for the porn industry.

Depending on how moralistic you might think NASA is, I would either have to say multiple times or at least once.  I am pretty sure that there was a married couple that were part of the crew together on at least one shuttle flight.  Don't think there have been any married couples on any of the Space Station crews.

So, if you think NASA would only condone religiously sanctioned sexual activities, I would say it has happened at least once.

Now a more interesting question might be, who will be the first 'Space Provider?'

I don't think Coco had a mate . . .

Can you imagine them swinging from the space shuttle, hanging upside down and making little chimpanzese {sic}?  I'd like to go ape with someone in the space shuttle.  Too much fun!

Hugs,
Ciara

Hell, I'd go up in a '32 Ford coupe, if I was promised 2 weeks of constant sex.