Shuttle's success gives NASA a morale boostCAPE CANAVERAL, Florida The U.S. space shuttle Discovery's successful return to Earth, complete with its distinctive double sonic boom and a whooshing glide to the runway, ended a nearly flawless 13-day mission.
It also marked the beginning of the end of the shuttle program, which President George W. Bush has ordered to be shut down by 2010.
Meantime, NASA is to perform 16 more shuttle missions to complete the International Space Station, the half- built orbiting laboratory that was the Discovery's destination in this flight, and will then embark on the president's stated goal of returning to the moon in a new generation of space vehicles.
The morale boost of a successful flight, after the loss of the shuttle Columbia in 2003 and a frustrating first test flight last year, was evident on Monday in the beaming smiles of the crew and NASA officials - even Michael Griffin, the self-described emotionless engineer who is the space agency's administrator.
Still, questions remain about whether the program has solved the safety problems that have plagued it over the years.
NASA managers said that the success of this mission reinforced their view that they could step up the tempo of launchings, with Atlantis returning to space as early as Aug. 28 and the mission after that beginning in mid-December.
Griffin cautioned at a news conference at the Kennedy Space Center, "We're not going to get overconfident."
Engineers and analysts will pore over the data from this flight in coming weeks and months, he said, to better understand issues like foam debris from the shuttle's external tank before launching the next mission.
The amount of foam shed during the Discovery's liftoff on July 4 - the problem that doomed the Columbia and continued to plague last year's return-to- flight mission -posed no threat.
The crew brought thousands of pounds of supplies to the half-finished space station and made three spacewalks in which they repaired broken equipment to allow the resumption of construction during future flights, and tested possible repair techniques.
They also carried up a new space station crew member, Thomas Reiter, a German astronaut from the European Space Agency.
The crew was led by the shuttle commander, Colonel Steven Lindsey, who was making his fourth trip to space and his second as a commander. The pilot, Commander Mark Kelly of the navy, was on his second shuttle mission. The two spacewalkers were Michael Fossum and Piers Sellers of England. The flight engineer, Commander Lisa Nowak of the navy, operated the robot arm during their spacewalks with Stephanie Wilson, who also supervised the transfer of tons of cargo between the two craft.
Experts on space policy also expressed relief that the mission had gone so well. "They've got the right stuff back," said John Pike, the director of Globalsecurity.org.
But he added that the success did not change the fact that the shuttle program itself was in its last phase.
"Mr. Bush has decided that Mr. Nixon's space shuttle and Mr. Reagan's space station are not the way he wants to go," Pike said. "He likes John Kennedy, going to the moon."
Warren E. Leary contributed reporting from Houston for this article, and John Files from Washington.