CAPE
CANAVERAL - Three
months before the planned launch of shuttle Discovery and seven astronauts,
NASA again is under dangerous pressure to fly so it can finish the
International Space Station by 2010.
Once again, NASA has delivered
a revamped external fuel tank to Kennedy Space Center before finishing
tests to prove whether it is safe to fly.
This time,
decisions will be colored by that mortifying moment last July when Discovery's
right wing was almost
struck by another chunk of orange foam insulation from the tank, a piece
similar to the debris that doomed
Columbia three years ago.
Managers
insist they will delay the launch if tests show conditions could lead to
another disaster, which would prompt an early shutdown of the shuttle program
and the loss of thousands of jobs in Brevard County.
"Is
there a potential that you would fly something that you have less than full
confidence in just because you're already going down the path toward
flight?" said John Chapman, manager of the external tank project at
Marshall Space Flight Center in Alabama. "The answer to that is absolutely
not.
"There
is absolutely zero intent to fly that tank before that work is complete. . . .
It's as simple as that."
However, a FLORIDA TODAY review of NASA documents shows that agency managers bowed to schedule
pressure during NASA's attempt to return the shuttle fleet to service after the
Columbia accident. The records show that some engineers argued for changes to
the part of the tank that shed foam on Discovery's flight, but were overruled
by managers.
The review
also showed:
- Discovery
was cleared for flight last year even though a redesigned external tank
failed to meet stricter safety standards set after the 2003 Columbia catastrophe.
- NASA
managers changed ground rules of crucial engineering analyses, avoiding
further modifications to a tank already at KSC.
- Discovery's
fragile heat shield suffered more debris hits than orbiters on prior
flights, but the damage was less severe.
In February 2003, Columbia's seven astronauts died when their shuttle disintegrated over Texas during
atmospheric re-entry. Investigators blamed a hole in the heat shield, caused
when a piece of tank insulation broke free during launch and struck the left
wing at high speed.
Today, this
much is clear: NASA never will be able to completely stop the foam insulation
from breaking free from external tanks in flight. But the agency has made
significant progress in preventing debris large enough to cause catastrophic
damage to an orbiter.
"You
guys ought to be aware, and we have got to make it clear to everybody we talk
to, when we launch the next flight, there is still going to be foam come off
the tank," shuttle program manager Wayne Hale told KSC workers in a
meeting last month.
"We
have not got a plan in place that is going to eliminate all foam loss off the
tank," he said. "That is a big goal, and we don't think we are going
to get there in the life of the program."
Near-hit
NASA
concedes the near-hit on Discovery averted the kind of damage that could have
triggered a risky rescue mission. Astronauts would have docked at the space
station and waited while NASA scrambled
to launch a second shuttle.
With
Discovery, a 3-foot (almost one-meter) slab of foam broke away from a long
wedge of insulation -- dubbed a Protuberance Air Load ramp, or PAL ramp --
designed to provide a wind shield for critical fuel pressurization lines and
electrical cables that run along the outside of the tank.
Two
independent review teams said schedule pressure played a role in decisions
about the extent of safety modifications the agency would attempt before
Discovery's flight last summer.
Lower-level
engineers flagged the 38-foot (11-meter) PAL ramp for removal, modification or
extra inspections. They knew the handcrafted wedge was susceptible to shedding
large chunks of debris.
It now
appears their suggested changes could have made a difference.
NASA
removed and replaced 10 feet (three meters) of the ramp to make other changes
in the area. On that section, workers used a new and improved process to
reapply the foam. The debris later shed during Discovery's launch came from the
28-foot part (8.5-meter) of the ramp that had not been replaced.
At the
time, managers planned to fly two more missions while engineers completed the
analyses.
Changing
rules
Discovery
was on
the launch pad at KSC last spring before NASA finished analyses aimed at
showing whether the redesigned tank met stricter new requirements for reducing
launch debris. The reviews ultimately showed the tank did not meet standards.
But rather
than change the tank itself, managers changed the ground rules for the debris
analyses. Several members of an independent oversight group took exception with
that approach.
"The
middle of a design review does not seem an appropriate time to be changing the
rules," they said in comments added to the Return
To Flight Task Group's final report. A NASA manager told them, "That's
why we're changing the models, so we don't have to change the tank."
Ultimately,
NASA conceded foam or ice debris large enough to cause catastrophic damage
still could come off parts of the modified tank.
A
post-flight inspection report shows that Discovery was battered by debris
during last July's flight.
A total of
176 dings and gouges were counted on fragile heat-shielding materials designed
to protect the orbiter and its crews from the intense heat of re-entry. The
average on previous flights: 144.
Armando
Oliu, the head of NASA's ice and debris inspection team at KSC, said the majority
of the damage was minor. That's a sign that the agency is making progress
toward eliminating the worst debris.
"We
know the external tank is producing the majority of those debris hits, but it's
from small particles," he said. "What we've reduced is the potential
for a major hit."
Modifications
NASA
managers decided late last year to remove
PAL ramp foam from the tank now being readied for the next shuttle flight.
Engineers think it will be safe to fly the tank without the ramp, but
conclusive tests and analyses are ongoing.
"Your
gut says it's probably an OK thing to do, but you don't want to bet the safety
of the vehicle on intuition," Hale said.
Wind tunnel
tests are under way in California and Ohio. Additional tests are scheduled in Tennessee in June. Discovery is set to launch July 1.
Hale says
he would postpone
the launch if the tests prove fuel pressurization lines or electrical
cables might be ripped off in flight without the PAL ramp to protect them.
"You
don't want to fool around with that because you can't stand for those things to
come loose when you go Mach 4. That would be a bad thing," Hale said.
"If the answer comes back and says the cable tray will come off, then
that's not something we're going to fly with."
Published under license from FLORIDA TODAY. Copyright ©
2006 FLORIDA TODAY. No portion of this material may be reproduced in
any way without the written consent of FLORIDA
TODAY.
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