HOUSTON SPACE CENTER, Texas - Two spacewalking astronauts armed with caulking guns, putty knives and foam brushes practiced fixing deliberately damaged shuttle heat shields Saturday, a job they hope they won't have to do for real. Although Discovery suffered some scrapes and chips during liftoff, none of the damage appears to warrant orbital repairs, space agency officials said. As the two astronauts completed the mission's first spacewalk, NASA was on the verge of extending Discovery's visit at the international space station. With future shuttle flights grounded because of Discovery's fuel-tank foam loss during liftoff, the space agency would like to...
