July 14, 2005

No shuttle launch before Sunday – NASA

By Deborah Zabarenko and Irene Klotz

CAPE CANAVERAL, Fla. (Reuters) - Space shuttle Discovery
will not launch before Sunday and probably will fly later than
that, NASA managers said one day after delaying the first
shuttle launch since the 2003 Columbia disaster.

Wednesday's much-anticipated launch was called off after
NASA engineers detected a faulty fuel sensor. Thursday was
devoted to troubleshooting that problem, said Wayne Hale,
deputy shuttle program manager.

Even a Sunday launch is unlikely, Hale said.

"If we were to get extremely lucky, it is theoretically
possible that we could still launch on Sunday," Hale said at a
briefing. "This represents a really optimistic, good luck
scenario which I think is not very credible."

NASA has until July 31 to launch Discovery, a deadline
dictated by its planned rendezvous with the International Space
Station and a new requirement that all shuttle launches take
place in daylight to let cameras capture images of liftoff.

The next window of opportunity for launch begins Sept. 9.

NASA aims to launch the shuttle this month to carry
supplies and equipment to the station, and to test new safety
upgrades put in place since the fatal Columbia accident.

All seven astronauts were killed when Columbia
disintegrated over Texas on Feb. 1, 2003. The direct cause was
a hole in the craft's wing caused by falling debris during
launch. However, investigators found a "broken safety culture"
at NASA that discouraged questioning of upper-level decisions
was also to blame.


NASA experts acknowledged the sensor problem -- which they
described as an intermittent event with no obvious cause --
represented a difficult challenge.

The faulty sensor is one of four that would cut off the
shuttle's three main engines if at least two showed that
hydrogen fuel was running low during flight. A premature cutoff
might damage the engines, force the shuttle to make an
emergency landing or leave it short of its desired altitude.

Wednesday's launch was canceled after engineers conducted a
routine test of the sensors and one failed. NASA engineers do
not know what caused the problem and are working through about
200 possible scenarios.

Problems with the sensors continued after technicians
drained Discovery's tank when Wednesday's launch was canceled.
Later, it accurately showed the tank was empty.

Intermittent, unexplained failures are the hardest to
troubleshoot, Hale said.

Letting Discovery fly without working to determine the
cause and fix the problem is not an option, Hale said: "Could
we talk ourselves into going without doing anything? No."

Peppered with questions from reporters, Hale defended
NASA's effort.

"Going into space is right at the limits of human
technology here at this point in the 21st century. We're doing
something that's extremely difficult. This is not like going to
the airport and getting on a commercial airline," he said.

"You are watching America do something that frankly most of
the world can't do, that only the most innovative and most
dedicated countries have the capability to do."

Discovery's crew stayed out of public view Thursday, after
being seen on Wednesday strapped into their seats and ready for
launch. They are expected to stay at Cape Canaveral if there is
a launch scheduled anytime through Tuesday.

The shuttle remained on the launchpad, partly obscured from
view by the remote servicing structure, a kind of movable
scaffolding that gives workers access to the vehicle.