Although the events that doomed the space shuttle Columbia may never be fully understood, investigators have focused on damage to thermal tiles inaccessible to the astronauts. In the future, says Robert Ambrose at NASA's Johnson Space Center in Houston, crews on the International Space Station or a shuttle might include a robotic repairman. NASA's "Robonaut" is getting close to realizing that vision. With its human-size palm, four fingers, and an opposable thumb, Robonaut is "phenomenally dexterous," says Alan Peters, a researcher at Vanderbilt University's Center for Intelligent Systems. "It has the best hands of any robot on the planet." This...