This shuttle/space station are bad science, and now, their management
problems are coming to light as well too.
So, isn't it time the two programs were cancelled? It sure it.
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July 31, 2005
For NASA, Misjudgments Led to Latest Shuttle Woes
By JOHN SCHWARTZ
This article was reported by John Schwartz, Andrew C. Revkin and Matthew
L. Wald and written by Mr. Schwartz.
"We are ready to fly."
It was June 24, and William W. Parsons, NASA's shuttle program manager,
was speaking to reporters on a telephone conference call from the
Kennedy Space Center at Cape Canaveral, Fla. Two and a half years of
study and struggle, he told them, were over at long last. The shuttle
Discovery could blast off in July.
At a closed-door meeting that afternoon, senior shuttle managers had
ruled that the chances that debris from the giant external fuel tank
would strike the Discovery at liftoff - in the kind of accident that
doomed the Columbia and its seven astronauts in February 2003 - had been
reduced to "acceptable levels."
The possibility that a large chunk of insulating foam might break away
from a section of the tank called the protuberance air load ramp - PAL
for short - never came up. It had been ruled out months earlier, checked
off on a long list of items no longer worthy of urgent action.
Last Tuesday morning, NASA's contention that it had produced the safest
fuel tank in shuttle history was shattered two minutes into the
Discovery's mission to the International Space Station. Two spacewalking
astronauts tested repair techniques at the station yesterday.
The 0.9-pound piece of foam that fell from the PAL ramp on liftoff,
which could have led to another catastrophe if it had ripped away a
minute sooner, forced the immediate suspension of future shuttle flights
until the problem could be resolved.
How did it happen? In hindsight, it is clear that the effort to resolve
the PAL ramp problem was a chain of missed opportunities and
questionable judgments, not just since the Columbia disaster but over
the life of the shuttle program.
Potentially useful tests were not performed. Innovative solutions were
not seriously pursued. Tantalizing clues were missed. In the end, the
old engineering maxim "If it ain't broke, don't fix it" trumped vague
misgivings about a part that had not shed any foam, as far as anyone
knew, since 1983.
"After two and a half years, they should have been able to fix the
foam," said Paul A. Czysz, a professor emeritus of aeronautical
engineering at St. Louis University and a veteran consultant to NASA.
Now, with the future of the space station in the balance and the shuttle
fleet just five years away from a mandatory retirement imposed by
President Bush, NASA is still trying.
The space shuttle's external tank is used for just eight minutes, then
ditched over the Indian Ocean. It holds more than half a million gallons
of liquid hydrogen and liquid oxygen, the highly volatile gases the
craft's main engines burn on the leap into orbit. The tank is covered
with plastic foam; without that, it would ice over with moisture sucked
from the Florida air.
At the dawn of the shuttle program, NASA rules said no foam at all
should be allowed to hit the shuttle and possibly damage the fragile
heat-resistant tiles that cover its aluminum skin.
But fidelity to those standards was relaxed over time; in fact, foam
fell from a PAL ramp in two early missions, including the one in June
1983 on which Sally Ride became the first American woman in space. There
may have been many more incidents, but dozens of shuttle missions have
been launched in darkness, with no visual record of foam, and the tanks
themselves cannot be retrieved from the ocean for analysis.
As the early tank was replaced with two lighter successors, the PAL
ramps remained - one a 19-foot baffle along a channel for cables and
pressurized lines along the forward end of the tank and the other the
37-foot strip along the flank of the cylindrical midsection of the fuel
tank. And as experience showed NASA that shuttles returned safely
despite well over 100 nicks and gouges requiring repair on many flights,
the concerns abated over time.
Until Feb. 1, 2003, the day the Columbia disintegrated on its way home
to Cape Canaveral.
It turned out that on liftoff, 16 days earlier, a 1.67-pound piece of
foam had fallen from the tank and struck the leading edge of the
shuttle's left wing. Despite years of assurance that such a strike could
do no serious damage - a mind-set the Columbia Accident Investigation
Board would call the "normalization of deviance" - the foam had cracked
open a hole that admitted superheated gases when the shuttle re-entered
the atmosphere, burning it up like a torch from within.
After the accident, NASA examined all possible sources of liftoff
debris, eventually identifying more than 170. Engineers recognized that
they could not eliminate all risk from debris, but they could do a much
better job of reducing it.
The PAL ramp became a focus of attention: like the bipod arm ramp, the
part of the tank implicated in the Columbia disaster, it is covered with
foam by hand. NASA conducted extensive wind tunnel tests to see whether
the ramp could be removed.
The wind tunnel tests of the ramp areas were all focused on aerodynamics
- helping determine how air would flow around the craft and tank, or to
improve understanding of where foam or ice or other debris might fly
should it fall free of the tank. But there were no tests of the PAL foam
itself at the speeds, pressures or vibrations of ascent.
So the only tests of how the ramp material might hold up under the rigor
of launching were the launchings themselves, with astronauts aboard.
For many aeronautical engineers, a central rule in developing an
aircraft is taking its components beyond the breaking point.
"If you don't break a wing, you just have assumptions about what might
make it break," said Aldo J. Bordano, a retired NASA aerosciences chief
who was on a panel that studied the agency's analysis of the external
tank and foam.
He said that while it was premature to conclude whether mistakes were
made, many panel members were frustrated with the lack of physical
testing of the foam under liftoff conditions.
In any event, NASA decided that the tank without the ramp would expose
the cables and hoses to destructive winds; agency engineers and managers
considered alternatives but could not come up with any that inspired
confidence.
"The community was very diligent about looking at this," Mr. Parsons
said in announcing the PAL ramp problem last week. "We did realize that
eventually one day we needed to put together a program to remove this
PAL ramp if at all possible. But at the time, we didn't have enough data
where we could technically do that and be safe."
There was no evidence that the ramp had shed foam since the early
1980's, he said, adding, "We had had very few problems with the PAL ramp
and we decided it was safe to fly as is."
To Professor Czysz, of St. Louis, that decision shows limited
imagination and NASA's tendency to look inward for answers.
"I think they tried to find the solution within their own ranks, using
what they're already familiar with," he said. "They should have looked
at more options," perhaps including different formulations of foam that
might be more flexible.
But as Michael D. Griffin, NASA's new administrator and an engineer
himself, said Friday, that would have violated the old tenet about
fixing what is not broken.
"We debated and discussed whether the PAL ramp was broke" in the months
that followed the Columbia disaster, he said. "The conclusion we came to
was the wrong one, but the conclusion we came to after considerable
study was that it was better to fly as is."
NASA engineers had already seen how fixes can break things. After they
made a minor change in the foam application process in the late 1990's
to comply with environmental rules, small divots of foam rained off of
the tank during ascent. The phenomenon, called popcorning, was caused by
trapped bubbles; NASA solved the problem by venting the foam with tiny
holes, but it was a reminder, if any was needed, that seemingly small
changes could have profound effects.
"Foam really is complicated," said Douglas D. Osheroff, a professor of
physics at Stanford and a member of the board that investigated the
Columbia accident. "Once you go supersonic, the top surface melts, the
bottom surface is brittle as all hell because it's very cold, and you've
got everything in between."
Although the material could be made less fragile by adding fibers to the
foam, he noted, "that adds weight" to the shuttle, and any changes can
take years.
Ultimately, the accident board recommended that NASA find ways to
prevent any shedding of foam or other debris. And NASA gained confidence
during the time between flights that it was making progress.
Among other things, it improved the training processes for applying foam
by hand. At the Michoud tank assembly plant in Louisiana, an observer
monitors every worker spraying foam - "for every sprayer there's a
watcher, a second pair of eyes," said June Malone, a NASA spokeswoman.
But the tank that flew with the Discovery last week was made before the
new procedures went into effect, and NASA stopped short of requiring
that the ramps be redone, said a spokesman, Martin J. Jensen.
After the Columbia accident board issued its scathing report on the
causes of the Columbia disintegration - especially a "broken safety
culture" at NASA that had grown complacent about all sorts of risks -
another independent group was set up to monitor the agency's progress in
fulfilling the accident board's safety recommendations.
That group, called the Stafford-Covey task force after the two former
astronauts who led it, accepted NASA's argument that the PAL ramp did
not urgently require alteration.
At its final meeting in June, however, it also found that NASA had
failed to meet the goal of eliminating all debris. The group took issue
with the way NASA determined that the foam chunks that might still fall
off the tank were too small to cause critical damage. And it criticized
the agency's tendency to depend on computer simulations when physical
experiments might yield more valuable data.
Ultimately, however, the group accepted NASA's contention that it had
raised the level of safety in general.
"You need to look at what the agency has done, not necessarily a
scorecard," said Richard Covey, a co-chairman. Indeed, the tank
modifications have reduced shedding, according to the array of cameras
and sensors installed in the wake of the Columbia accident, to 25 nicks
and dings counted after the Discovery's liftoff from the usual 145.
On Friday, Mr. Covey, who was pilot of the first shuttle mission after
the 1986 Challenger accident, said that in light of the PAL ramp
incident, his group, too, had erred - but added, "We certainly weren't
any smarter, at that point, than the folks who were working it on the
NASA side."
He agreed with the contention of NASA officials that the Discovery
mission was a test flight that would provide data for further
improvement. "You learn," he said, "and then you go fix and then you fly
again."
A NASA engineer who works on tank safety issues said other areas of foam
shedding from the Discovery's tank were even more troubling than the PAL
ramp loss, especially a divot that popped from the vicinity of the
left-hand bipod strut, the spot that shed the foam that brought down the
Columbia.
"We worked the hell out of that," said the engineer, who was given
anonymity because he said disclosure of his name would jeopardize his
career. The loss of foam from that spot after so much work to correct
the problem, he went on, proves that the problem is still far more
complex than NASA understands.
So the space agency is back to the drawing board. Some of the options
under consideration have come up before, including the elimination of
the ramp, a "miniramp" that shrinks the size of the strip by two-thirds,
and a small "fence" on the opposite side of the tray that would smooth
airflow further. Another possibility, rotating the tank so the ramp
faces away from the shuttle, would take years, engineers say.
Dr. Griffin, the NASA administrator, predicted Friday that the foam
problem would be quickly repaired and said engineers would consider
options that had not been tried before. But he added that the next
generation of spacecraft would place cargo and crew members atop the
tank and not on its side, where falling foam and ice invite disaster.
"As long as we put the crew and valuable cargo above the tank, we don't
care what they shed," he said. "They can have dandruff all day long."
Dr. Jon Clark, widower of the Columbia astronaut Laurel Salton Clark,
said the Discovery incident should be a warning to NASA. He is still a
"big fan of the shuttle," he said. But "at some point you've got to say,
'Wow, maybe the critics who say this is a really flawed design are right.' "
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