CAPE CANAVERAL, Fla. - For the
second time in two weeks, NASA is just hours away from launching the space
shuttle Discovery, the agency's first space shuttle to fly since the Columbia
catastrophe.
Discovery sits atop Pad 39B here at
Kennedy Space Center (KSC) - its external tank filled with
super-chilled fuel - as engineers carefully track readings from vital engine
cut-off sensors inside the tank's liquid hydrogen section. It was
one of those hydrogen sensors, ECO sensor No. 2, which failed a standard pre-launch
countdown test during Discovery's initial July 13 launch attempt. Since flight
rules call for four functioning sensors in order to launch, shuttle officials scrubbed
the attempted space shot.
"We've gone through so much in the
last couple of weeks, and it's discouraging," Discovery's vehicle manager
Stephanie Stilson
told SPACE.com. "It's impossible not
to be discouraged when something you've been working for is postponed."
But today is a different story.
"It's going to be an very exciting time,"
astronaut Dave Wolf said of Discovery's second launch attempt, adding that
while attention may have dropped after Discovery's first scrub, today's launch
will be sure to make a mark. "The eyes of the world are going to be on KSC."
Mission managers believe that the extensive
investigation into the fuel sensor glitch over the last two weeks has given
them a good understanding of the anomaly, even if they still cannot fully
explain it. During that time, pad engineers found and addressed wiring
grounding issues inside the orbiter's ECO sensor electronics box, tested and
retested potential sources of electromagnetic interference and rewired two of
the ECO sensors - No. 2 and No. 4 - to better isolate the glitch should it
occur again.
Two additional tests, spaced out
throughout the countdown, should verify the sensors' performance, NASA
officials said. The first will take place about 30 minutes after pad engineers begin loading the external tank with its cryogenic fuel. A second test is scheduled during a planned countdown hold at T minus 9 minutes, NASA officials said.
Mission managers have even drawn up plans
to launch Discovery should the sensor glitch pop up again, so long as it does
so according to specific guidelines which have been discussed exhaustively.
"I think we're all struggling with
the ghost of Columbia," said Wayne Hale, deputy program manager of the shuttle
program, during a pre-launch briefing late Sunday. "We want to do it right."
The space shuttle Columbia broke apart over
Texas, its seven astronaut crew lost, during atmospheric reentry on Feb. 1,
2003. Investigators pinned the accident on launch debris that pierced
Columbia's protective thermal shield, as well as a sense of complacency and
schedule-mindedness pervading through NASA's internal culture.
The family members of the astronauts
lost aboard Columbia, as well as relatives of those astronauts lost in the 1986
Challenger disaster, are expected to attend today's
space shot, NASA officials said. Other dignitaries include First Lady Laura
Bush, Florida Gov. Jeb Bush and family, Gen.
Forrest McCartney - a Columbia accident investigator, as well as artist Barbara
Erst Prey, Congressman Dave Weldon (R-Florida) and
Sen. Tom Feeney (R-Florida) and others.
NASA has spent the last two and a
half years working to address its internal culture and return its three
remaining shuttles - Discovery, Atlantis and Endeavour - to flight status.
Commanded by veteran astronaut
Eileen Collins, Discovery's STS-114 space shot is the first of two test flights
- Atlantis' STS-121 mission is expected to follow in September - to shakedown
new tools and procedures developed to increase shuttle flight safety. The
orbiter bears a sensor-laden extension for its robotic arm, which STS-114
astronauts will use to check the orbiter's sensitive areas for damage. An
extensive network of still and film cameras, as well as radar, is in place to
scrutinize every phase of the launch. Even the astronauts aboard the
International Space Station will play a part, photographing the orbiter
"I'm probably not quite as excited
because [July 13] was the real one," Stilson said of the upcoming
launch. "But it's building back up for me."
Meanwhile, Discovery's sistership
Atlantis is mated to its own external-tank launch stack and primed to roll out
to the launch pad on Aug. 3. The shuttle rolled out if its Orbiter
Processing Facility and into the Vehicle Assembly Building on July 22.
Shuttle officials prepared the
Atlantis for its STS-121 spaceflight in tandem with the work on Discovery in
order to have a back up spacecraft to retrieve the STS-114 crew from the ISS.
That rescue plan, known as Contingency Shuttle Crew Support (CSCS) or "safe
haven," calls for Atlantis to launch on a mission dubbed STS-300 by Aug. 22 in
the unlikely event that Discovery suffer extensive damage and is
unable to return to Earth safely.
"We were processing for STS-121, for
a [space] station flight...if in the slim chance we were called up for STS-300,
we'd just go," Atlantis vehicle manager Scott Thurston told SPACE.com. "I dare say folks are more
excited now than for STS-114 because now we have two shuttles ready to go...it's
a good thing that we're flying again."
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