NASA: Space shuttle cracking finally understood
CAPE CANAVERAL, FL
Discovery's final voyage has been on hold since the beginning of
November. If the remaining repair work goes well, the shuttle could
fly to the International Space Station as early as Feb. 24.
At a news conference, NASA officials refused to discuss the
flight status of astronaut Mark Kelly, the husband of Rep.
Gabrielle Giffords, who was shot in Arizona last weekend. He's
supposed to command shuttle Endeavour's last mission in April. His
identical twin brother, Scott, is currently serving as the space
station's skipper.
"Out of respect to the family, we really are not ready to
answer those questions today. We're going to let Mark decide really
kind of what he needs to do," said Bill Gerstenmaier, head of NASA
space operations. "Our hearts and prayers go out to the family,
and we're really thinking about Mark in everything we do."
On the orbiting lab, Scott Kelly took a call Tuesday from
Russian Prime Minister Vladimir Putin.
"There are no people in Russia who are not touched by this
terrible news," Putin said through a translator.
The Endeavour mission is the last on NASA's official shuttle
flight lineup before the fleet is retired. The space agency hopes
to add one last trip to the space station by Atlantis at the end of
August to bring up extra spare parts, provided there's funding.
Officials initially were targeting the end of June for the launch,
but said Tuesday they would prefer more time between flights.
As for Discovery's prolonged grounding, shuttle program manager
John Shannon said a combination of inferior material and assembly
issues is to blame. Cracks occurred in five of the 108 aluminum
alloy struts in the center of the tank, which holds instruments.
The damaged struts have been patched. Technicians will reinforce
the remaining struts as a safety precaution, using thin 6-inch
strips of aluminum.
Shannon called it "a very simple, elegant fix to the problem."
"We're going to fly with a lot of confidence in this tank," he
told reporters. "We've gotten rid of the uncertainty."
The tank is covered with foam insulation, and NASA was concerned
the cracks could force pieces to break off during liftoff, with
chunks possibly striking the shuttle. A slab of foam doomed
Columbia in 2003.
Engineers also worried that if four or more struts in a row
failed, the entire structure could catastrophically buckle.
The cracking was discovered after an unrelated problem -- a
hydrogen gas leak -- halted Discovery's launch countdown on Nov. 5.
Shannon said a batch of the material used for some of the
21-foot support struts, through heating, ended up more brittle.
In addition, weaknesses were introduced during assembly of the
pieces.
The bad batch of material likely ended up on the fuel tank that
launched Atlantis last May, Shannon said. Every indication is that
the tank performed normally, even if cracks were, indeed, present,
he noted.
The tank currently being prepared for Atlantis also has struts
made of the suspect material and will need to be repaired.
Engineers believe Endeavour's tank is unaffected, but extra tests
are likely, which would push that mission into mid- to late April.
Once the 30-year shuttle program ends, the White House wants
NASA focusing on expeditions to asteroids and Mars, rather than
servicing the space station.