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The U.S. space shuttle Discovery has landed in Florida, ending a
resupply and maintenance mission to the International Space Station. Its
successful flight means the space agency NASA can finally resume
construction of the station.
Discovery's safe landing is an
obvious relief to NASA, which was forced to halt assembly of the
half-built space station more than three years ago when the shuttle
Columbia disintegrated upon re-entry into the atmosphere.
Discovery, sounding like any other airplane, glided smoothly onto a
runway at the Kennedy Space Center in Florida.
After landing, shuttle commander Steve Lindsey inspected the spacecraft
and declared it free of damage, after its nearly nine million-kilometer
journey.
"This is my fourth flight, and I've done four
walk-arounds, and I've never seen a vehicle that looked as clean as this
one did," said Steve Lindsey.
That is important to NASA, because it worked more
than three years to ensure that shuttles suffer as little damage as
possible from the kind of launch debris that doomed Columbia. That orbiter
burned up when searing
atmospheric gases entered a hole in its wing, caused by hard foam
insulation that broke away from the external fuel tank during liftoff and
hit it.
As a result, NASA removed or reshaped several areas of tank foam,
installed an array of ground cameras to monitor launches, and put new
cameras and sensors on shuttles to detect possible launch debris strikes
or hits by micro-meteoroids while in orbit.
NASA chief Michael Griffin attributes Discovery's near-pristine
condition to these new measures and a bit of luck.
"This is as good a mission as we've ever flown, but we're not going to
get overconfident," said Michael Griffin. "We have to take it flight by
flight."
During Discovery's two-week flight, two spacewalking astronauts tested
new procedures to make repairs in orbit to the shuttle's fragile heat
shield. The orbiter also transported a third crew member to the space
station, which had only two since Columbia's accident. Station manager
Mike Suffredini says it also hauled up new supplies and equipment, and its
crewmembers made repairs to station systems critical to resuming the
outpost's construction.
"So with this flight, in our minds, we are ready to get on with
assembly, and we will do just that," noted Mike Suffredini.
Station assembly restarts late next month, when the shuttle Atlantis is
to deliver a pair of solar energy panels, new batteries and a truss
segment on which to mount other components.
NASA chief Griffin points out that shuttle flights
are always risky and that station assembly missions are the most
complicated that shuttles fly. He says only 16 shuttle flights remain
before the fleet is retired in 2010, and more orbiter troubles could be
ruinous
for the space station's
construction schedule.
"We don't have any slack [leeway]," he said. "We have just enough
shuttle flights left to do the job. So, we can't afford to mess up."
Griffin thanked America's international partners in the space station
program for their patience and support, while NASA took time to make
shuttles safer to fly.
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