This
story was updated at 10:00 p.m. EST.
NASA
mission managers delayed the planned February launch of the space shuttle
Discovery for the third time late Friday, with liftoff now slated for no earlier
than Feb. 27 pending the completion of ongoing fuel valve tests.
Mission
managers will review Discovery's launch readiness during a planned Feb. 20
meeting to determine if the shuttle is prepared to fly a
two-week construction flight to the International Space Station by Feb. 27.
If so, the shuttle would be primed for a 1:32 a.m. EST (0632 GMT) liftoff on
launch day, NASA officials said.
The new
delay will give engineers more time to complete a series of impact tests on
shuttle fuel control valves at several NASA centers across the country, agency
officials said. NASA announced the new launch delay after a day-long review on
Friday to discuss the ongoing tests.
"As you can
expect, with any issue of this complexity, there's a tremendous amount of data
that's being collected," said Kyle Herring, a NASA spokesperson at the Johnson
Space Center in Houston. "In fact, data was coming in from testing during the
meeting."
Valve
tests ongoing
Discovery
was initially slated
to launch on Feb. 12, but last week mission managers delayed the launch by
one week, then again to no
earlier than Feb. 22, to allow engineers extra time to evaluate the
shuttle's fuel control valves.
There are
three fuel control valves on a space shuttle - one for each main engine. They
are designed to pop up much like a lawn sprinkler head to route gaseous
hydrogen fuel through a set of plumbing lines and into a hydrogen reservoir
inside the orbiter's attached 15-story external tank. The valves ensure a
shuttle's hydrogen tank maintains the proper pressure during the 8 1/2-minute
launch into space.
During the
November launch of the shuttle Endeavour, engineers found that a chip from one
of the metal valves broke free and flew into the plumbing lines leading to the
external tank. The incident did not hinder Endeavour's launch, which reached
orbit successfully.
But NASA
engineers want to be sure that a similar event, if it occurred during
Discovery's launch, would not puncture the shuttle's vital plumbing lines and
cause catastrophic damage.
NASA
engineers have been working long hours for the last three weeks to perform
high-fidelity impact tests using shuttle equipment. NASA's space shuttle
program manager John Shannon wanted to give them more time to analyze the data
before discussing an official launch target during the flight readiness review
meeting on Feb. 20, Herring said.
"They
wanted a little more time between the [flight readiness review] and the launch
date to close out, if they need to, any open items," Herring said.
Commanded
by veteran spaceflyer Lee Archambault, Discovery's seven STS-119 astronauts
plan to swap out one member of the space station's crew and deliver the final
set of U.S. solar arrays to boost the orbiting lab's power grid during their
mission. Four spacewalks are planned for the spaceflight.
Launch
limitations
Discovery
has until March 12 to launch toward the space station and begin its 14-day
construction flight. If the shuttle is unable to fly by then, NASA would stand
down until after a Russian Soyuz spacecraft launches a new crew to the station
around March 26, Herring said.
Earlier
Friday, astronauts aboard
the International Space Station said that while they were looking forward
to the arrival of Discovery's crew, they were more than willing to wait until
mission managers decide it was safe for the shuttle fly.
"We have
complete confidence that they'll make the right decision on flight rationale
based on solid data," space station commander Michael Fincke of NASA radioed
down to Mission Control at NASA's Johnson Space Center in Houston.
Discovery's
delay means a longer stay in space for NASA astronaut Sandra Magnus, a station
flight engineer who has lived aboard the orbital outpost since last November.
Magnus is
due to return to Earth aboard Discovery after nearly four months in space. Her
replacement, Japanese astronaut Koichi Wakata, will arrive aboard the NASA
shuttle to join the station's Expedition 18 crew, then stay on to serve with
the next crew - Expedition 19 - when it arrives in late March.
Wakata, a
veteran spaceflyer, is Japan's first long-duration astronaut. He is due to
return to Earth aboard another NASA space shuttle later this summer.
Discovery's
STS-119 mission is NASA's first of up to six scheduled shuttle flights of 2009.
The other missions include several space station construction flights and the
final overhaul of the Hubble Space Telescope.
The
shuttle's delay is not expected to affect the planned May 12 shuttle launch
toward the Hubble Space Telescope and a subsequent space station construction
flight, NASA officials said.
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