Space is devoid of the stuff humans need to live: air, gravity, hot showers, fresh veg, privacy, beer. How much can a person give up? What happens when you can't walk for a year? Is sex any fun in zero gravity? As Mary Roach discovers, it's possible to explore space without ever leaving Earth. From the space shuttle training toilet to a 17,000-mile-per-hour crash test of NASA's space capsule, she takes us on a surreally entertaining trip into the science of living in space.