Cape Canavarel, Fla. ? The shuttle Discovery and its crew of six returned safely home Monday, rejuvenating a space program that until now had been vexed by the same chronic foam problem that brought down Columbia three years ago.

Within hours of the smooth touchdown, NASA was already looking ahead to the next shuttle launch in just six weeks and, with it, the long-awaited return to construction work on the half-finished space station.

“It’s a good day,” NASA Administrator Michael Griffin said. “It’s an awfully good day.”

Discovery’s commander, Steven Lindsey, who took a walk around the shuttle after landing, said he had never seen one look so clean and undamaged after a spaceflight. It was a striking achievement for a launch that was challenged by some within NASA who wanted more improvements to protect the spacecraft from flyaway foam insulation.