CAPE
CANAVERAL, Fla. - NASA's planned launch of the space shuttle Discovery is
suffering an extended delay, with engineers still puzzled over a fuel sensor
glitch that scrubbed an attempted space shot two days ago.
"Right now
we are on a day-by-day basis until we find and fix the problem," said Wayne
Hale, NASA's deputy shuttle program manager, adding that once a fix is made,
Discovery could launch four days later. "What is that date going to be? I don't
know."
NASA had
hoped to launch Discovery and its STS-114 astronaut crew on July 13 after a two
and a half year hiatus from shuttle flight that followed the 2003 Columbia disaster that destroyed one orbiter and killed seven astronauts. The mission,
designed to test new tools and techniques for shuttle flight safety, could
launch by late next week, but only if engineers are able to not only isolate
the anomaly, but fix it fast.
"That would
require a very near-term, lucky find," Hale said during a press briefing here
at NASA's Kennedy Space Center (KSC). "But we are not in any sense of the word
pessimistic about making the July [launch] window. We are here for the
duration."
NASA has
until July 31 to launch Discovery if it is to make the current launch window
under shuttle flight restrictions. Clear, daylight views of Discovery's launch,
external tank separation and docking at the International Space Station (ISS) are
required to track any debris or damage to the orbiter's thermal protection
system. To get those views, NASA must launch the orbiter by the end of the
month or wait until the next launch window for those conditions, which opens on
Sept. 9.
Flight
controllers scrubbed
Discovery's July 13 launch after a fuel level sensor inside the orbiter's
external tank failed a standard countdown test. The sensor, one of four used to
measure liquid hydrogen fuel levels inside the external tank, tracks propellant
during launch to make sure Discovery's main engines shut down before the tank
runs dry. If the sensors don't perform properly during launch - reporting a
full status when the tank is dry, or an empty status when fuel still remains -
it could spell disaster for the shuttle and its crew.
Engineers
aren't sure whether the faulty sensor readings detected during the July 13
countdown are the result of a bad sensor, wiring problems or the complicated
electronics box inside Discovery that processes the sensor readings. If the
problem is with the box, NASA does have a spare, but that unit has voltage
issues and it could take anywhere between 10 days and three weeks to build a
new one, shuttle officials said earlier this week.
Twelve
teams of engineers are working through the weekend to try and pin down the fuel
sensor anomaly.
"We need to
know that the problem doesn't have implications for more sensors," said John
Muratore, manager of space shuttle systems and engineering at KSC, adding that
engineers must tread softly inside Discovery. "Every time we go into the ship
to do something, there's...the risk of damaging something we can't repair."
The sensor
problem has come up before, on a different external tank, which shuttle
engineers mated to Discovery and later filled with fuel during an April tanking
test. But after wiring and electronics box adjustments, and a second tanking
test that showed no sensor glitches, the matter was deemed an "unexplained
anomaly."
Now, Hale
said, shuttle engineers will do as much as possible to understand the current
problem before they consider flying with it unresolved.
"We're off
to try to find this problem and solve it, not fly with some unexplained
situation," he added.
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