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NASA shuttle fleet will stay grounded
Fuel line fractures delay space flights for 2 more months
Copyright 2002 Houston Chronicle
Graphic: Shuttle safety concerns 
NASA's space shuttle fleet will remain grounded for at least two more
months while experts look for the cause of small but potentially
catastrophic fuel line cracks, a top space flight program official said

Earlier this week, engineers completed inspections of Atlantis,
Discovery, Columbia and Endeavour that revealed a total of 11 fractures
in the metal plumbing that channels hydrogen fuel to the rocket engines
aboard each of the spacecraft. 

"We are not going to fly until we are satisfied we understand this
problem," said Ron Dittemore, NASA's shuttle program manager. Dittemore
is leading the wide-ranging probe as well as coordinating a strategy to
repair the fractures and resume launches as soon as possible. 

The space agency suspended launches on June 24 after technicians at the
Kennedy Space Center in Florida found three cracks on both Atlantis and

The grounding prompted inspections of Columbia and Endeavour as well as
the immediate delay of a July 19 research mission aboard Columbia that
was also to mark the first flight of an Israeli astronaut. The suspension
threatens to disrupt a pair of assembly missions to the international
space station slated for August and October. 

So far, the space agency has not calculated how much the grounding is
costing the $3.2 billion a year shuttle program. However, Dittemore said
Friday NASA has kept its work force busy making as many preparations as
possible for the upcoming missions. 

The safety concern is that the cracks might cause pieces of the thin fuel
lines to break away during a shuttle's near nine-minute ascent to orbit
and flow into a high speed rocket engine turbo pump. The debris could
cause sensors in the pumps to shut off an engine prematurely, forcing the
astronauts to attempt an emergency landing. In the worst case, the debris
could trigger an explosion. 

Nonetheless, Dittemore said Friday the results of the probe so far
suggest the safety threat may not be as great as he initially feared. The
presence of cracks on all four shuttles suggests the fractures were
present during previous spaceflights. 

Endeavour, the newest of the shuttles that first flew in 1992, was just
as susceptible to the cracks as Columbia, the oldest which launched for
the first time in 1981. Endeavour, which has the fewest flights, 18, has
the same damage as Discovery, which has flown the most with 30 missions. 

The space agency is assessing a range of theories about the cause of the
damage. They include the possibility the metal alloy fuel lines contained
tiny manufacturing flaws when they were first installed or that the
installation procedure itself caused a stress that became a crack. 

The cracks vary in length from one-tenth to three-tenths of an inch. Only
two of the 11 found penetrate all the way through the thin fuel line

The flaws were so small that only five of the fractures were evident in
unaided visual inspections. The rest required the use of ultrasound
devices and other special equipment to detect. 

Dittemore said NASA has not ruled out the possibility the shuttles could
continue to fly with the cracks if experts can pin down the cause and
assure shuttle managers the fractures will not grow. Regardless of
whether the fuel lines require repairs or not, the inspection procedures
will be strengthened, he said. 

The most recent shuttle flight, a trip to the space station, ended on
June 19. 

The current suspension is the longest since 1999 when the shuttle fleet
was grounded for five months. That setback was triggered by an electrical
short aboard Columbia. 

As NASA investigated, it found damage to the insulation of electrical
wiring strung throughout the fuselage of each spacecraft and initiated
extensive repairs before flights resumed. 
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