And then there’s our favorite space sex rumor: according to G. Harry Stine, an engineer and well-known rocket science popularizer, “clandestine experiments” have been conducted in NASA’s neutral buoyancy tank, confirming beyond doubt that “it is indeed possible for humans to copulate in weightlessness.” But, says Stine, an anonymous source informed him it works best with a third swimmer to “push at the right time in the right place.” People who executed this particular maneuver in orbit called themselves the “Three Dolphin Club” and even had a membership pin.

— City on Mars di Kelly Weinersmith, Zach Weinersmith (Page 74 - 75)