Shuttle returns home safely

But NASA needs to solve problem of breakaway foam insulation before further launching further flights.

CAPE CANAVERAL, Fla. - Seven astronauts returned safely to Earth in California Tuesday after 14 days in space on the first shuttle mission since the Columbia disaster.

"Discovery is home," NASA commentator James Hartsfield announced as the shuttle landed without incident at 8:11 a.m. EDT, capping the first of two test missions in NASA's return to flight effort.

"We're happy to be back and we congratulate the whole team for a job well done," commander Eileen Collins radioed mission control from the cockpit as the shuttle rolled to a stop before dawn on a three-mile- long runway at Edwards Air Force Base in California.

Discovery was supposed to touch down near its launch site at Kennedy Space Center, but low clouds and lightning along the Florida coast two days in a row forced mission managers to reroute the returning crew.

The shuttle mission was the first on NASA Administrator Michael Griffin's watch, and he had high praise. "I'm thinking of resigning my position in favor of Eileen Collins," he joked at a news conference at Kennedy.

The mission featured an eight-day visit by Discovery to the International Space Station, where the shuttle crew unloaded supplies, picked up trash and conducted an emergency spacewalk to repair their winged ship's heat shield.

Last Wednesday, astronaut Stephen Robinson rode a robot arm to the underside of Discovery to pluck two protruding pieces of filler material from the surface of the black-tiled heat shield. Officials feared the gap fillers would cause the shield to overheat during re-entry.

Tuesday, about two hours after touchdown, the astronauts climbed out of Discovery to greet well-wishers on the runway and Robinson strolled beneath the orbiter to show his crewmates the results of his handiwork.

Heat shield damage brought down the shuttle Columbia, killing seven astronauts, as the orbiter returned to Earth in February 2003. The damage was caused by a piece of foam insulation that popped off Columbia's fuel tank and punched a hole in its left wing during liftoff.

NASA spent two years redesigning parts of the fuel tank in an effort to prevent foam loss, but a one-pound chunk of foam broke free from the Discovery's tank during its ascent.

Shocked mission managers ordered extra inspections during the flight, but found no damage. However, the inspections did reveal that the tank lost five pieces of foam that were bigger than NASA deems safe.

"That I know of, that's the only thing that went wrong with this mission in any imaginably significant way," Griffin told reporters in Florida. "It's going to be hard to top this mission."

NASA has grounded the shuttle fleet again so that engineers can delve deeper into the foam-shedding problem and find a way to stop it for good. The next shuttle mission, originally scheduled for September, has been postponed indefinitely.

Griffin said NASA will make a valiant effort to return shuttles to flight before the end of the year. "We have a big construction project and we need the shuttle to do it," he said, referring to the unfinished $30 billion International Space Station. "But we're not going to go until we're ready."