This story was updated at
4:09 p.m. EDT.
CAPE CANAVERAL, Fla. - NASA
managers decided Monday to continue preparing for the planned July 4th
launch of the space shuttle Discovery, even as engineers evaluate a piece of foam
insulation that popped free from the spacecraft's fuel tank.
A team of engineers is
poring over a small piece of foam about three inches long which cracked, then
fell, from a bracket connecting a 17-inch feed line that supplies super-cold
liquid oxygen to Discovery's engines from its orange external tank.
The foam piece is small,
weighing just 0.0057 pounds, less than half of the upper limit - 0.013 pounds -
for acceptable debris during a shuttle launch, NASA said.
"It looks like this small
piece of bread crust," said John Shannon, NASA's deputy shuttle program
manager, during a press briefing here at the Kennedy Space Center (KSC). "What
we decided to do was continue with the plan that we were on."
That plan, Shannon said, is to complete the loading of
cryogenic fuel aboard Discovery to power the spacecraft during its planned
STS-121 spaceflight. Meanwhile, tank engineers will analyze whether Discovery
can fly with the lost foam on July 4, or if the shuttle will require
inspections and repairs at its Pad 39B launch site.
Results from that study
will be presented during a Mission Management Team (MMT) meeting at 6:30 p.m. EDT (2230 GMT), which is led by Shannon, where a final decision will be
made.
"Getting to it is not an
issue, but it would be a schedule hit to us," said NASA launch director Michael
Leinbach. "We cannot accomplish getting access to this area and also support
the launch tomorrow morning. It's just not possible.
Discovery
is currently scheduled to launch Tuesday at 2:37:51 p.m. EDT (1837:51 GMT) on NASA's STS-121 mission to the
International Space Station. The planned spaceflight is NASA's second shuttle
flight since the 2003 Columbia accident.
Shannon said Discovery's STS-121 crew has
been notified of the foam concern. The mission's commander Steven Lindsey asked
several questions during a short MMT meeting earlier today, with the rest of
the crew briefed later, he added.
Falling
foam
Fuel tank
foam loss has been a great concern for NASA since the loss of the space shuttle
Columbia, which suffered a heat shield breach by a chunk of the insulation and
was destroyed during reentry - its seven-astronaut crew lost - on Feb. 1, 2003.
Since then
NASA engineers worked to streamline the amount of foam on shuttle fuel tanks,
replacing some insulation with heaters after the Columbia accident and removing one large section altogether after
the 2005 launch of Discovery's STS-114 mission.
The piece
of foam found by inspectors Monday fell from the topmost of a series of brackets
connecting a liquid oxygen feedline to Discovery's external tank. That top
bracket is just above and to the right of the bipod fitting that mates
Discovery to its fuel tank.
"It looks
like it just came off all in one nice piece from the crack," Shannon said.
By NASA's
current understanding, Sunday rain showers - which led to that day's launch
scrub - led to condensation on a bracket joint that froze into ice from the
super-cold liquid oxygen inside the nearby feedline.
That ice
later pinched into the surrounding foam as Discovery's external tank warmed and
expanded, a normal occurrence as engineers emptied the 526,000 gallon vessel of
its super-chilled liquid oxygen and liquid hydrogen.
John
Chapman, NASA's external tank project manager, said inspectors discovered the
crack during a routine examination conducted after every launch scrub.
The piece
fell sometime during that three-hour inspection, and was seen by engineers as
they moved the protective Rotating Service Structure into place around
Discovery, he said.
Current
concerns
NASA officials said that
the liberated piece of tank foam seen today could not have damaged Discovery's
heat shield during a launch.
"It would not have been an
issue," Shannon said. "It is less than half the size that we think can cause
damage to the orbiter."
Shuttle managers don't
believe the foam loss will impact the ability of Discovery's fuel tank to
withstand the heating stresses it will experience during launch. Analysis is
still underway to determine whether any other cracks or damage are afflicting
tank bracket.
The potential of ice to
form over the area exposed by the foam loss is also a concern, since major foam
loss or ice debris could be a hazard for the black, heat-resistant tiles lining
Discovery's belly.
"I do know that we have
more insulation in this area than we absolutely needed," Chapman said, adding
that analysis is underway to evaluate the ice concern. "I expect that that
analysis will show [we're] good."
NASA's STS-121 MMT meeting
will meet at 6:30 p.m. EDT (2230 GMT) today. The results of that meeting are
expected to be released later this evening.
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