This
story was updated at 5:35 p.m. EST.
NASA's
planned launch of the space shuttle Discovery this month has slipped a few more
days to Feb. 22 due to extra time needed to finish tests related to newly installed valves
on the spacecraft, agency officials said Friday.
Discovery
was slated to launch no earlier than Feb. 19 pending the completion of tests to
ensure the shuttle's three fuel flow control valves are safe to fly. But work
at several NASA centers to evaluate the valves in time for a Tuesday meeting by
shuttle managers is taking longer than planned, and shifted the launch to no
earlier than Feb. 22, according to an update released late Friday.
Mission
managers are now expected to discuss the valve test results on Feb. 13, and
then meet again on Feb. 18 to review the Feb. 22 launch target, said NASA spokesperson Kyle Herring at the agency's Johnson Space
Center in Houston. That process, however, is wholly dependent on the progress
and results of the valve tests, he added.
Earlier
this week, NASA delayed Discovery's
initial Feb. 12 launch date by at least a week due to concerns with the
spacecraft's flow control valves.
There are
three flow control valves on Discovery - one for each main engine - designed to
route gaseous hydrogen from the engines to a propellant tank in the orbiter's
external tank to maintain proper pressurization during the launch into space.
During
NASA's last
space shuttle launch in November, one of the valves aboard the Endeavour
orbiter was damaged, sending a small chip about the size of a thumbnail tip
into the plumbing lines leading back to the external tank. Endeavour
successfully reached orbit and maintained fuel tank pressure despite the
glitch. Engineers found a crack in the suspect valve after Endeavour returned
to Earth.
An initial
analysis suggests that acoustic vibrations may have led to high-cycle fatigue of
a valve component that pops up and down like a lawn sprinkler head, NASA's
space shuttle program manager John Shannon told reporters late Tuesday. Similar
valves aboard Discovery were replaced with ones that have flown previously and
are known to be in good shape, he added.
Even so,
mission managers ordered a round of tests to better understand how metallic
chips from the valves could affect plumbing lines leading back into Discovery's
fuel tank during flight.
"We
want to make sure we've got this right," said NASA's space operations chief Bill Gerstenmaier late
Tuesday. "So we think standing down a little bit of time, and letting the
folks do a little more work is a good thing."
Commanded
by veteran spaceflyer
Lee Archambault,
Discovery's STS-119 mission is NASA's first of up to six shuttle flights
scheduled for 2009. The two-week mission includes four spacewalks to deliver
the last set of U.S.-built
solar arrays to the International Space Station and replace a member of the
orbiting laboratory's Expedition 18 crew.
A series of
additional space station construction flights, as well the final shuttle
mission to overhaul
the Hubble Space Telescope, are also slated to launch this year.
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