This story was updated at
9:03 p.m. EDT.
HOUSTON -- NASA officials
have grounded the agency's remaining space shuttles after the Discovery
orbiter's external tank shed chunks of foam, including one
piece more than 2 feet long.
The problem is similar to
what occurred in the disastrous Columbia flight in 2003 and was thought to have
been fixed.
Space shuttle officials said
that while there is currently no indication the foam contacted the Discovery orbiter, the incident should not have happened in the first
place and is reason enough to put a hold on future flights.
Images taken of the external
tank in orbit identified the foam separation, and also detailed additional
areas where the material pulled loose from its tank, they said.
"Until we've fixed
this, we're not ready to fly," said Bill Parsons, NASA's space shuttle
program manager, during a press briefing here at Johnson Space Center.
"You could say that we're grounded."
The Discovery orbiter and
its STS-114 crew launched into space Tuesday morning and are approaching the
International Space Station (ISS), where they will dock early Monday.
It is NASA's first shuttle
to fly since the loss of the space shuttle Columbia in 2003, which was fatally
struck by falling foam debris during launch. The briefcase-sized foam chunk hit
Columbia's left wing back then, gouging a hole in its heat shield that led to
the orbiter's destruction -- and the deaths of all seven astronauts aboard --
during reentry on Feb. 1, 2003.
The foam shed during
Discovery's Tuesday launch originated on a protuberance air load (PAL) ramp
that juts out from the orange external tank and protects vital cables, wiring
and pressure lines running along its length. Current estimates place it between
24 and 33 inches long at its longest point and up to 8 inches wide.
'We need to do
better'
NASA has spent
two-and-a-half years redesigning portions of the shuttle's external tank to
prevent exactly such foam loss, and early discussions on the need to address
the PAL ramp -- which is swathed in thick foam layers -- ended with engineers
believing no changes were needed. External tank project manager Sandy Coleman
said the modifications had resulted in "the safest, most reliable tank we
have ever built" for the shuttle program when the first of three new units
were delivered to NASA's Kennedy Space Center in January 2005.
The tank used by Discovery
in Tuesday's launch was the second of those tanks delivered.
"We need to do better
than this," said Wayne Hale, deputy shuttle program manager, during the
briefing, adding that it was fortunate the incident occurred when it did.
"If this had happened earlier, it would have been bad."
Because of Discovery's high
altitude at the time of the PAL foam loss, there was not enough air to sweep it
back fast enough to impact the orbiter, Hale added.
The space shuttle Atlantis,
being prepared to launch in September, will not fly before shuttle engineers
fully understand and address the PAL ramp foam loss, shuttle officials said,
adding that they did not know if any fix could be implemented in the next
month, three months or by the end of the year. Discovery was slated to fly
after Atlantis.
NASA's third, and last,
remaining shuttle -- Endeavour -- is currently in its major modification
period.
Today's announcement came at
the end of a day in which Discovery's astronaut crew spent hours conducting a
methodical inspection of their spacecraft's nose cap and wing leading edges
using a new orbital boom sensor system (OBSS). Capped with a
video camera laser sensors, the boom is designed to inspect the
shuttle's vital reinforced carbon carbon panels and
heat-resistant tiles that safeguard the orbiter and its crew from the extreme
heat of reentry.
"We feel very confident
of Discovery's thermal protection system, but we are looking into this,"
Parsons said.
Additional foam loss,
known tile damage
Handheld images taken by the
STS-114 crew of the external tank also revealed other incidents of unexpected
foam loss.
In addition to the PAL ramp
incident, a chunk of foam separated near the tank's bipod structure, where its connected to the forward section of Discovery. Shuttle
officials made modifications to the foam application in that region, and were
surprised to see foam loss there, Parsons said.
"We need to take
another look at that," he added.
A short distance beneath the
bipod, in a region known as acreage foam, another small
divot appeared. Acreage foam is applied to the external tank by machine, a
process NASA engineers made no changes two in the last two years.
"Personally, I'm
disappointed," Parsons said of the foam loss, but added that it was
advantageous that it occurred without harming Discovery. "We learned
something. What if this hadn't happened and we flew five, six or seven
[missions] down the line?"
NASA already knew they had a
chipped tile near Discovery's nose landing gear doors.
Hale said that images taken
by an external tank-mounted video camera caught the small chip flying off
Discovery during the launch. Also in the image was a small white area on the
shuttle's belly that will be an "area of interest" when the orbiter
exposes its underside to the space station astronauts for photographs.
"Are we concerned?
We're treating it very seriously," Hale said of the apparent tile damage.
"Are we losing sleep at night? Not yet."
The STS-114 crew will likely
train the cameras aboard the orbital boom sensor system on the chipped tile
region during a three-hour block of time on July 29 already set aside for
follow up inspections to Discovery's thermal protection system, Hale added.
Astronauts notified
The crews of both Discovery
and the International Space Station -- where two astronauts plan to take
extremely high resolution images of the shuttle's tile-covered belly early
Thursday - have been notified, and data packages uplinked
to their vehicles for analysis, Parsons said.
"They were very glad to
get [the data] and there will be more discussions about it tomorrow,"
Parsons said.
While no new space shuttles
will fly for the time being, NASA will not stop preparations for the follow-up
to Discovery's mission, the STS-121 spaceflight aboard the Atlantis orbiter.
Atlantis is already mated to its own external tank-solid rocket booster launch
stack, and was slated for a Sept. 9 liftoff before today's foam find. NASA also
tapped Atlantis to serve as a rescue ship for the STS-114 crew in the remote
chance Discovery were too damage to return home and its astronauts forced to
take shelter aboard the space station. That contingency rescue mission is known
as STS-300.
"We think the need for
an STS-300 is remote at this time," said Wayne Hale, deputy shuttle
program manager, during the briefing.
But Parsons said that should
it be needed, the decision would be "very difficult."
Meanwhile, Discovery's crew
was sleeping Wednesday evening and is expected to awaken at 11:39 EDT (0339
GMT) and prepare to dock at the ISS. That docking is slated for 7:18 a.m. EDT
(1118 GMT) on July 28.
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