A mere three years after Burt Rutan´s SpaceShipOne skimmed the edge of space to capture the $10-million Ansari X Prize, more than half a dozen companies are furiously building and testing spacecraft designed to take paying passengers on suborbital journeys and beyond.

Although they may have other talents, few astronauts are much good at sleeping in space. NASA researchers have been studying the problem by hooking up space shuttle crews to all sorts of sleep-monitoring devices. The mystery remains unsolved, but one surprising discovery has been made: There's virtually no snoring in space.