With a firm
testing plan in hand and its fuel tank factory back on track, NASA is targeting
May 2006 for the launch of its next space shuttle mission.
The May
launch target, while not set in stone, will allow engineers time to complete a
series of tests to determine why potentially dangerous chunks of foam
insulation broke free from the shuttle Discovery's external tank during its
July launch, NASA officials
said. They believe that a combination of worker-caused damage, old application
techniques and other factors appear to have contributed to the debris event.
"We don't
say we're setting a launch date, but we're clearly aiming for May," said Bill
Gerstenmaier, NASA's associate administrator for space operations, during a
Friday press conference. "May looks very doable."
A 20-day
launch window opens on May 3 for the space shuttle Discovery, NASA officials
said, adding that more discussion is needed before the window becomes a firm
flight target.
NASA
officials previously aimed at March
2006 to launch the second post-Columbia accident flight - STS-121 aboard
the Discovery - but said today that recovery
efforts from Hurricanes Katrina and Rita led to a loss of about three
months of work.
The storms battered NASA's
Michoud Assembly Facility in New Orleans, where external tanks are built and
investigators were studying the foam shedding issue, and the surrounding area,
though the plant itself did not suffer the worst damage, NASA officials said.
"Our biggest
problem, frankly, at Michoud is not the damage to the plant," said Wayne Hale,
NASA's space shuttle program manager. "It's the damage to the workers' homes."
More than
500 workers of Michoud's 2,000-person strong workforce have resumed their
duties, NASA officials said. The facility's workforce is expected to return to
its full strength by Dec. 1.
"Final
schedule setting will depend on how soon the workforce can get back online,"
Hale said of NASA's STS-121 launch plans.
Tracking
debris shedding
A one-pound
piece of foam insulation broke
free from protective ramp during Discovery's July 26 launch, but did not strike
the orbiter. NASA, however, had worked for 2 ˝ years to prevent the shedding of
large foam debris after Columbia
disaster that killed seven astronauts on Feb. 1, 2003.
During Columbia's launch, a 1.67-pound piece of foam fell from its fuel tank and gouged a hole in
the protective heat shield along the orbiter's left wing leading edge. The
resulting damage allowed hot atmospheric gases to enter the wing during reentry
and rip the vehicle apart.
Richard
Gilbrech, who is leading NASA's "tiger team" investigating the foam shedding
problem, external tank workers may have inadvertently crushed or cut foam along
a protuberance air load (PAL) ramp, which shields exterior tank cables and
pressurized lines during launch, while instituting post-Columbia accident fixes.
An
older spray application technique - instead of a newer, enhanced method - and
thermal stresses along the seam of where PAL foam meets acreage foam, may also have
contributed to debris shedding on Discovery's tank, Gilbrech said.
"I
don't know if we'll ever identify one root cause," Gilbrech said.
Engineers
plan to conduct tests to determine how much force is required to crush foam, as
well as perform non-destructive tests on the next external tank to fly - ET-119
- which NASA shipped
to Michoud last month. Tank workers will also remove ET-119's PAL ramp and
slice it into 1/8th-inch pieces to further study the foam's
integrity, NASA officials said.
Those
tests and others must be completed before the fuel tank is shipped back to
NASA's Kennedy Space Center (KSC) for Discovery's STS-121 flight, they added.
"Before
we set an official launch date, we've got to get through some of the near term
work," Hale said. "I think we're beginning to get our hands well around the
problems we have."
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