July 14, 2005

NASA engineers race clock to fix shuttle flaw

By Michael Christie

CAPE CANAVERAL, Fla. (Reuters) - NASA engineers were
working against the clock to find out why a fuel sensor
mysteriously malfunctioned on the space shuttle Discovery after
the problem delayed the first shuttle mission since the
Columbia accident 2 1/2 years ago.

The U.S. space agency has until July 31 to launch Discovery
before it will have to postpone until Sept. 9 an attempt to
rendezvous the spacecraft with the International Space Station.

Any delay substantially beyond that could threaten
construction of the space station and perhaps even NASA's
longer-term plans to head back to the moon, to Mars and deeper
into space.

NASA engineers at Kennedy Space Center in Florida and at
Johnson Space Center in Houston began work overnight to try to
find out why the hydrogen fuel sensor failed.

Officials said they hoped to identify the cause by late
Thursday, and the next launch attempt might occur on Saturday.

But they acknowledged that malfunctions occurring
intermittently, with no obvious reason, rather than
consistently, represented one of their worst nightmare.

"It does at this stage remain an unexplained anomaly. It
reminds me of an old truck I owned with an intermittent
electrical problem," said deputy shuttle program manager Wayne

"Unexplained anomalies are the worst ones."


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. A premature cutoff might damage
the engines, force the shuttle to make an emergency landing or
leave it short of its desired altitude.

Shuttle Discovery's planned liftoff this month from Cape
Canaveral marks the first shuttle mission since its sister ship
Columbia fell apart over Texas in February 2003, killing all
seven crew.

Falling foam from Columbia's external fuel tank had knocked
a hole in its wing at liftoff 16 days before. The shuttle
disintegrated when superheated gases tore into the breach on
re-entry into the Earth's atmosphere.

Delays caused by bad weather and technical problems have
bedeviled shuttle launches in the past. But this mission has
gained wider attention than most because the fleet of three
remaining shuttles has been grounded since the Columbia

NASA managers said their readiness to call off Wednesday's
scheduled launch even after Discovery's seven-member crew had
been strapped into the spacecraft reflected a new aversion to
risk in the wake of the Columbia disaster.

In addition to testing new safety measures and experimental
heat shield repair techniques, Discovery will take much needed
supplies and equipment to the space station.

The 16-nation project has been on hold since Columbia
crashed because the U.S. shuttles are the only spacecraft
capable of lifting heavy components to orbit.

NASA aims to keep the shuttles flying until 2010 so the
space station can be completed. The aging shuttles will then be
retired and replaced by a new generation of spacecraft capable
of reaching the moon and perhaps Mars.

While engineers worked to fix the hydrogen fuel sensor,
Discovery's crew, led by veteran commander Eileen Collins,
remained in Cape Canaveral to continue training flights.

Should the delay extend beyond Saturday, the astronauts
would probably return to Houston, NASA said.