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NASA wrestles with same old problems for shuttle

Still can't keep foam from flying off external tank

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 five days away, NASA is dealing with many of the same problems it faced almost a year ago.

The shuttle program manager, Wayne Hale, acknowledges that, but contends that progress is being made. ``In terms of the foam, we are so much smarter this year than we were last year," he said.

However, NASA is still unable to stop foam 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 2 1/2-year hiatus that followed the Columbia disaster.

NASA has spent at least $1.2 billion on changes to the shuttle since 2003.

For the upcoming launch, set for Saturday, 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.

A Massachusetts woman, Stephanie Wilson, 39, will be one of the mission specialists on the flight. The Pittsfield native is a graduate of Harvard College and received a master's degree in aerospace engineering from the University of Texas.

Along with Navy Commander Lisa Nowak, Wilson will operate the shuttle's 50-foot robotic arm, attached to a 50-foot boom, during inspections for any damage to Discovery.

``It's very difficult to know where all parts of the arm and boom are at any particular time," said Wilson. ``That sometimes becomes the tricky part."

The mission will be led by commander Steve Lindsey, an Air Force colonel who has flown in space three previous times.

The other crew members are: Navy Commander Mark Kelly, the pilot; Michael Fossum, mission specialist; Piers Sellers, mission specialist; and Thomas Reiter, an astronaut with the European Space Agency.

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, however, favored flying without more changes but with plans to make the modifications in the future.

``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."

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," he said.

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.

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.

Discovery's mission, like the previous one, is considered a test flight. Astronauts will try different methods of inspecting the vehicle for damage. Any missions that follow this will be dedicated to finishing construction of the space station.

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 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 of cargo and trash.

Sellers and 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.

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