Working in outer space has been compared to climbing a mountain in scuba gear. Tough on astronauts-and dangerous. One solution: Let robots do it. NASA's Johnson Space Center is working on a handy humanoid robot that's designed to live and work in the void. So far, says project leader Robert Ambrose, NASA has built only one arm of the "robonaut." That's the key component, though. Packed with 19 motors and 150 sensors, the arm has dexterous digits designed to grab tools, railings and other space stuff designed for human hands. The robonaut's first assignment could be outside the International Space Station, where it would address equipment snafus, remote-controlled by humans inside the station. Ambrose says the robonaut, which won't be space-ready for at least four years, could eventually serve on interplanetary missions or help fix satellites in high orbit.