CAPE CANAVERAL - NASA set
out Tuesday on a second phase of repairs to shuttle Atlantis' hail-battered
external tank, work that will determine whether the agency can resume
International Space Station construction as planned in early June.
Normally done with robotics
in the factory, the unprecedented
work requires technicians to spray an aerodynamically smooth layer of
thermal insulation on the curved portion near the top of the bullet-shaped
tank.
Engineers built mock-ups
and developed step-by-step procedures to prepare for the high-precision
repairs, and technicians practiced manual sprays. NASA has never flown a tank
repaired with this technique.
"There's a lot of
confidence that everything is going to go smoothly," said June Malone, a
spokeswoman for NASA's Marshall Space Flight Center in Huntsville, Ala.
The work is critical to
NASA's plans
to launch Atlantis and seven astronauts around June 8 on a mission to
deliver a new 17.5-ton truss segment to the international outpost.
The launch had been
scheduled for March 15 but was postponed when the shuttle's 15-story tank sustained
serious damage during a Feb. 26 hailstorm.
Technicians already have
fixed more than 2,100 of some 2,600 dents, divots and gouges in foam insulation
covering the central and lower portions of the tank.
NASA also is inspecting the
orbiter's main propulsion system propellant lines in an effort to spot any
contamination that could trigger an engine failure in flight.
The inspections follow the
discovery of four small pieces of silicon rubber within one of the three main
engines that flew on a shuttle last December. Debris in a propellant line could
degrade engine performance or, in a worst case, lead to a catastrophic failure
in flight.
Engineers are using
snake-like devices tipped with cameras.
The tank repairs and engine
inspections are scheduled to be complete before the shuttle returns to launch
pad 39A around May 15. About 22 days of routine launch preparations are
required at the pad, so the schedule for a June 8 flight is tight.
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