In video footage, the astronauts aboard space shuttle Atlantis gleefully float tools and a miniature football in midair. They look like they're having fun. They're also coping with the million-and-one annoyances of the weightless lifestyle. The truth about zero-g, as the astronauts call it, is that it's a major pain.
  In weightlessness, "two things are easier"—carrying heavy items and fitting into small spaces—and "everything else is more difficult," says astronaut Scott Kelly, who last flew on the shuttle in 2007.
  The problems posed by zero gravity can make it harder for the crew, especially rookies, to get things done. That's no small matter now that shuttle missions are jammed with so much work that the astronauts have little time for sleep and meals...