This story was updated at 1:40 p.m.
EDT.
NASA's
first space shuttle to fly since the Columbia disaster will not liftoff until
July, a drastic delay that will force mission managers to miss the first of two
launch windows this summer.
Space
shuttle officials are now targeting a launch window opening July 13 for the space shuttle
Discovery, after it became clear that lifting off during the current window -
which runs from May 22 to June 3 - would be unattainable. The new launch window
closes July 31.
"We're
going to return to flight, we're not going to rush to flight," said NASA chief
Michael Griffin in a press conference at the space agency's Washington, D.C.
headquarters. "We're going to do it right."
Unresolved
debris issues, malfunctioning external tank sensors and soiled thermal
protection blankets contributed to Discovery's launch delay, which will push back preparations to deliver a large cargo pod to
the International Space Station (ISS). The delay will also allow more time to develop
plans to service the Hubble Space Telescope, Griffin said.
The space
shuttle is sitting atop launch pad 39B at NASA's Kennedy Space Center (KSC) in
Florida as part of the agency's first return to flight mission STS-114. A
countdown test with the crew and orbiter stack is scheduled for next week at
KSC.
The STS-114
flight is slated to test a host of new tools and techniques designed to
increase shuttle flight safety, a direct response to the loss of the Columbia
orbiter and its seven-astronaut crew. Columbia broke up during reentry on Feb.
1, 2003, which investigators later determined was a result of wing damage
caused by external tank debris shed two weeks earlier at the mission's launch.
"Every time
we've established a launch date, it's been on the best data available," said
William Readdy, NASA's spaceflight program chief, during the press conference.
"Since we first established a launch date in June 2003, we've adjusted it a
half a dozen times based on new data."
Ice debris and sensor glitches
It was new
data on the potential danger of ice debris striking the shuttle that pushed shuttle
managers to set the new launch date. The ice, which tests have shown can break off in chunks of up to five inches long, forms on regions of a 17-inch wide
liquid oxygen feed line running down the external tank.
Tank
engineers had previously installed a drip lip to the area of most concern - a bellows
unit that expands and contracts - which reduced the risk of ice by about 70
percent, NASA officials said.
"A very
small piece of ice can cause problems," said NASA shuttle program manager
William Parsons said in a separate briefing today from Johnson Space Center
(JSC) in Houston. "Ice does not cause the same damage foam...we understand foam
much better because we've done a lot of testing."
The damage
to Columbia's wing leading edge was caused by a briefcase-sized chunk of insulation
that separated from the external tank during liftoff. Tank engineers have since
redesigned portions of the tank to reduce the amount of foam shedding.
"The
testing on the ice lagged behind the testing on foam, but was clearly put in
place," said Wayne Hale, deputy shuttle program manager at JSC, during the
briefing. "But we had plans on how to deal with it [and will] now that we know
that we have to do something about it."
Shuttle
engineers could install a removable heater to the bellows area to prevent ice
build-up. The heating unit is already expected to ride on the third external
tank to fly, and will likely be installed on another tank already inside NASA's
52-story Vehicle Assembly Building to iron out assembly processes before a unit
is attached to Discovery's fuel tank.
But Hale
said that heater assembly kits won't arrive at KSC until May 5, and there still
remains some testing to determine if they will ultimately fly aboard Discovery.
Earlier
this month, shuttle mission managers and launch workers performed a critical
test of Discovery's revamped external tank, fueling it with 500,000 gallons of
liquid oxygen and hydrogen which the orbiter burns to reach space.
During that
test, problems were detected in two of the tank's four fuel sensors, used to
measure liquid hydrogen propellant levels, for reasons engineers still do not
fully understand. Four functioning fuel sensors are required in order to launch
the shuttle, Readdy said.
"I assure
you that four [sensors] of four is the launch commit criteria of STS-114 and
STS-121," Readdy added.
The
follow-up to Discovery's test flight, the STS-121 mission aboard Atlantis will also
test a series of new procedures and technologies for enhanced shuttle safety.
Other concerns
also included the accidental contamination of Discovery's thermal protection
blankets with hydraulic fluid, though Parsons said those concerns have been
lessened and the blankets could be cleaned, or even left alone, after further study.
ISS support and Hubble
Discovery's
two-month launch delay will also affect space station operations, where
Expedition 11 astronauts Sergei Krikalev and John Phillips were anticipating
the shuttle's May arrival to bring a wealth of food, supplies and new science
equipment.
NASA's
space shuttle fleet has been grounded since the Columbia accidents, leaving
space station crews dependent on Russian Soyuz spacecraft to reach the ISS and
the automated Progress vehicles for cargo deliveries. Discovery will deliver a
large cargo container to the ISS, as well as large station components that
currently cannot be launched aboard any other spacecraft.
William
Gerstenmaier, NASA's ISS program manager, said more water - currently the key
consumable aboard the station - would be added to a Progress vehicle set to
launch in June.
"Each one
of our international partners was disappointed that we're not going to launch
the shuttle in that first window, but I think they understood clearly why we're
doing it," Gerstenmaier said.
During the earlier briefing today, Griffin told reporters that
he had already informed key members of Congress Thursday evening that he would
direct engineers at Goddard Spaceflight center to start preparing for a space
shuttle servicing mission to Hubble on the assumption that one ultimately will
go forward.
Griffin said a final decision is still pending NASA's
successful return to flight with the launch of the shuttle Discovery. However,
with that launch now delayed nearly two more months, Griffin said the Goddard
team has to get started now to preserve the option of saving Hubble before the
popular telescope is scheduled to go dark around 2008.
"[But] We're not going to allow Hubble preparations to
interfere with return to flight," Griffin said.
Space News Staff Writer Brian Berger
contributed to this report.
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