CAPE CANAVERAL, Fla. — A grounded space shuttle. Countless months trying to fix foam insulation problems on the fuel tank. A faulty fuel tank sensor that delayed a launch in May.
If this list looks familiar, it should.
With a possible liftoff of Discovery just seven days away, NASA is dealing with many of the same problems it faced almost a year ago in what could be called the space agency's version of the movie "Groundhog Day."
The shuttle program manager, Wayne Hale, acknowledges that. But he contends progress is being made. "In terms of the foam, we are so much smarter this year than we were last year," he says.
Smarter, but still unable to stop it from flying off the shuttle's external tank. It's the same worrisome problem the space agency has wrestled with since falling foam damaged Columbia in 2003 and caused the deaths of seven astronauts.
Despite a redesign of the tank, foam continued to drop off last year during the launch of Discovery. That foam loss caused NASA to ground the shuttle fleet for almost a year — another delay after the 2½-year hiatus following the Columbia disaster. NASA has spent at least $1.2 billion on changes to the shuttle since 2003.
For the upcoming launch, set for July 1, engineers have modified the tank even further by removing about 35 pounds of foam in areas where a foam chunk dropped off last year. NASA describes the removal of the foam as the greatest aerodynamic change ever made to the shuttle's launch system.
"Foam will come off. There's no way around that. It is an expected event," said John Chapman, NASA's external tank project manager. "Our objective is to make sure if it does come off, it comes off in small enough pieces that it doesn't cause any harm."
Debate over design changes
Some at NASA think there should be even further design changes with more foam removal before a shuttle flies again.
At a meeting two weeks before the expected launch, leaders with NASA's Office of the Chief Engineer and Office of Safety and Mission Assurance recommended that the shuttle not fly until further design changes had been made to the tank. NASA Administrator Michael Griffin decided to have the shuttle fly without more changes, but with plans to make the modifications in the future.
A design with greater amounts of foam removed from the tank didn't test well in wind-tunnel trials.
Discovery's commander, Steve Lindsey, said he was encouraged by the forthright design debate since NASA was criticized after the Columbia disaster for squelching dissent.
"Both sides were listened to, very vocally and very publicly," Lindsey said. "You had a group of engineers who said, 'Change it.' Managers decided, 'Don't change it.' I guess time will tell which side was really right."
Armed with data from each new flight, NASA managers and engineers plan to make changes to the foam on the tank before each future flight until the fleet is grounded in 2010. The next-generation vehicle isn't expected to fly until around 2014.
NASA managers have acknowledged that another fatal mistake could ground the three remaining shuttles before the international space station is finished being built. It also could rule out any chances of a repair mission to the Hubble Space Telescope.
"Look, if we go fly and have another accident, that will be the end of the program," Hale said recently. "I'd rather not fly and say we couldn't get our act together ... than rush into some ill-advised launch where we had a catastrophe."
One postponement already
Discovery's 12-day mission, which will be only the second shuttle flight since the Columbia accident, already was postponed once, from May to July. A faulty fuel tank sensor was blamed _ much like it was last summer when a similar problem forced NASA to delay launching Discovery by several weeks.
Since Discovery's flight last year, technicians also have replaced or removed almost a third of the shuttle's 16,000 gap fillers. During last year's mission, two of these heat-resistant strips came loose, jutting from the shuttle's belly, and an astronaut had to remove them in a high-stakes spacewalk to avoid any harm to the shuttle on its return flight.
Discovery also has stronger insulation tiles around the vulnerable spot of the nose landing gear door, a sturdier tire and wheel system and new cameras attached to the solid rocket boosters that can capture more images of falling foam or other dangers to the shuttle and crew.
Efforts to get the shuttles flying again weren't just hampered by technical problems but by Mother Nature and a series of worker accidents.
Hurricane Katrina caused almost half a billion dollars in damage to two southern facilities where rockets are tested and designed. At Kennedy Space Center, Discovery's robotic arm was bumped by a platform.
Discovery's mission, like the previous one, is considered a test flight. Astronauts will be loaded up with experimental tasks, trying different methods of inspecting the vehicle for damage. Any missions that follow this will be dedicated to finishing construction of the space station before the shuttle is retired — with the possible exception of that mission to service the Hubble.
Space station chores
Once at the station, Discovery will be leaving one of the seven astronauts behind. The European Space Agency's Thomas Reiter will return the international space station to a three-man crew for the first time since early 2003.
The shuttle crew also will deliver 5,100 pounds (2,300 kilograms) of cargo, including an oxygen generation system that can support a space station crew of six, and a laboratory freezer. They will haul back 4,700 pounds (2,100 kilograms) of cargo, including lots of trash.
"We have a lot of stuff onboard the space station that we need to get rid of," said U.S. flight engineer Jeff Williams, who currently lives on the station along with Russian commander Pavel Vinogradov.
Astronauts Piers Sellers and Mike Fossum will make two spacewalks, with a third one possible, adding an extra day to the mission, to test repair techniques on the space shuttle's thermal protection system. It will be Fossum's first spacewalk.
The spacewalkers will replace a cable connecting the space station's external railroad car and test the stability of a boom for use as a platform for shuttle repairs. The 50-foot (15-meter) boom, hooked to Discovery's 50-foot robotic arm, will swing the astronauts to various parts of the station and shuttle.
"You're standing at the end of it at night, so you'll feel like you're standing on a diving board or standing at the top of a telephone pole or hanging down from a ceiling," Sellers said. "It's disorienting, there's no question ... You won't always know which way is up."
Backup plans in place
Discovery's astronauts also will gather 3-dimensional images of their ship's wings and nose cap using a laser imager at the end of the boom. From the space station, Williams will photograph images of the shuttle's underside as it does a flip before docking.
If something looks suspicious, the astronauts can try to repair any damage during a spacewalk. In a worst-case scenario, the astronauts could stay at the space station for 81 days until a rescue shuttle is sent up to bring the crew back. Space shuttle Atlantis, the potential rescue vehicle, is scheduled to be moved to the launch pad in late July.
NASA managers said they'll only breathe easily once Discovery returns safely to Kennedy Space Center.
"We are home free only when the wheels stop rolling on the runway," Hale said.
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