The last time NASA was repeatedly questioned on the matter was in 1992 when married partners Mark Lee and Jan Davis (below) flew together on Space Shuttle mission STS-47.

Still, rumors persist and questions remain: Has it been done? How is it done? Is it permitted? Is it safe? 

While it is impossible to determine the validity of these claims, to boldly go where no humans have gone would require quite an elaborate mating ritual-not to mention, experts say, a good deal of caution.

In theory, the mechanics of zero-g sex would entail an array of bungee chords, elastic belts and other devices to ensure space lovers don't accidentally fly away from each other in the heat of passion.