 |  | "Go Fever" And Challenger Lessons: Agency Chooses Safety Over Schedule
By Todd Halvorson
Cape Canaveral Bureau Chief
posted: 07:00 am ET
19 January 2001
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CAPE CANAVERAL, Fla. – Shuttle
Atlantis headed back to its Kennedy Space Center (KSC) assembly building
Friday, a clear sign that NASA is walking the walk – and not just talking
the talk – when it comes to the agency’s "safety-first" mantra.
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| Shuttle Atlantis is prepared in the VAB for its STS-98 mission in January 2001.
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| The U.S. Destiny science lab is lifted out of its Florida work platform for a planned January 2001 launch.
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| The STS-98 Shuttle Atlantis astronauts crew portrait.
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| |  | Fifteen years after the ill-fated
Challenger flight, a dangerous rocket booster problem prompted senior shuttle
managers this week to delay the planned launch Friday of Atlantis rather
than risk a $2 billion spaceship, a $1.4 billion science lab and the lives
of five astronauts.
Independent aerospace safety
experts, meanwhile, are applauding the three-week postponement – a delay
that comes amid an intense agency push to ramp up NASA’s $60 billion International
Space Station construction project.
"It was a very sensible,
safe thing to do," said Seymour Himmel, a member of the Aerospace Safety
Advisory Panel, an independent group charted by Congress to oversee NASA
aeronautical and spaceflight programs.
"It’s not an easy thing –
with all the flights lined up for station construction – to roll the shuttle
back to its assembly building and take a real [schedule] hit. But I think
NASA did the right thing."
What’s more, Himmel and other
experts say the slip to Feb. 6 is representative of a conservative agency
mindset that is significantly different than the one which led to the January
1986 Challenger explosion, which killed seven astronauts.
"It’s a far cry from violating
your own [safety] rules, which was done when they agreed to fly Challenger,"
Himmel said.
Perched atop a giant tracked
transporter, Atlantis crept off its launch pad and into KSC’s 52-story
Vehicle Assembly Building so that NASA can inspect suspect cabling associated
with its solid-fuel rocket booster-separation system.
The cable concerns arose
during exhaustive inventory inspections that were ordered after a serious
glitch cropped up during the Nov. 30 launch of sister ship Endeavour on
a station construction mission.
On that flight, a pyrotechnic
cartridge designed to separate the shuttle’s left-hand solid rocket booster
from its 15-story external tank failed to fire. A backup cartridge worked
as advertised, and the booster separated cleanly.
Had the backup failed, however,
Endeavour and its five-man astronaut crew almost certainly would have been
killed in a Challenger-like catastrophe.
The reason: A strut attaching
the booster to the lower part of the tank would have failed to separate.
The massive fuel reservoir would have ruptured as a result, triggering
an explosion a little more than two minutes into flight.
Next page: The results
of 'wiggle tests' and other inspections
~
Engineers subsequently traced
the problem to a faulty cable designed to route critical computer commands
to the pyrotechnic cartridge. Clear evidence of damage due to normal wear
and tear had gone undetected during preflight inspections.
The close call prompted extra
inspections on separation system cables hooked up to Atlantis’ twin booster
rockets, and the shuttle ultimately was cleared for a Jan. 3 move to launch
pad 39A.
At the same time, though,
exhaustive inspections of all separation system cables in NASA’s inventory
were being conducted. Four faulty cables subsequently were discovered during
those inspections, raising new concerns about the integrity of Atlantis’
separation system.
Like the cables on Atlantis,
the suspect quartet from stock inventory had passed X-ray examinations.
The inventory cables, however, failed extra tests designed to simulate
the ability to relay crucial separation commands when the wiring is subjected
to launch-like vibrations.
The cause of the test failures
still is not understood.
The Atlantis cables, meanwhile,
had not been put through the extra "wiggle tests," which call for the wires
to be jerked from side to side and up and down while electrical power is
being transmitted through them.
And that fact raised red
flags with many within NASA’s shuttle program.
"We could not get comfortable
with the fact that what we had at the pad had not been [put through wiggle
tests]," NASA shuttle program manager Ron Dittemore said.
That’s not to say, however,
that there wasn’t a spirited discussion over the matter.
With the Atlantis crew waiting
to fly to KSC and countdown clocks poised to pick up, a teleconference
was convened Monday with officials from KSC, Johnson Space Center in Houston
and Marshall Space Flight Center in Huntsville, Alabama.
Engineers presented test
data that showed 194 cables containing 3,028 electrical conductors had
been examined. Problems, however, only were discovered with four of the
conductors, which are designed to relay separation commands.
What’s more, three of those
four conductors were spares that only would have been pressed into service
if primary conductors failed to route signals to pyrotechnic charges.
Some engineers, consequently,
felt the odds of a failure in flight were remote at best, and that NASA
should press ahead with its launch plans.
"We had some statistical
analysis that we had performed that indicated, based on statistics alone,
that you might be comfortable proceeding with flight," Dittemore said.
"And there were a number of folks that felt comfortable with just a statistical
analysis."
But engineers from Marshall
– where the booster project is managed – argued for extra inspections to
make certain the cabling on Atlantis isn’t prone to failure.
"There was another camp that
felt that even though the statistical analysis [showed] we might be justified
to proceed, the hardware was telling us something," Dittemore said.
"We had four failures here
that we discovered in our testing, we don’t understand yet why, and [they
felt] we ought to listen to what the hardware may be trying to tell us
and do further inspections."
In the end, Dittemore said,
"the prudent thing to do was to go back and inspect."
The decision-making process
-- and the ultimate decision -- stand in stark contrast to the fateful
call made by NASA managers the night before Challenger’s 10th and final
flight.
Faced with an equally ambitious
shuttle flight schedule, engineers from NASA Marshall and booster builder
Morton Thiokol Inc. held a teleconference to discuss the ramifications
of record cold weather on rubber O-ring seals in Challenger’s solid-fueled
rockets.
Thiokol engineers were concerned
that the O-rings – which are designed to prevent hot gases or flame from
escaping the boosters – might not work properly.
Postflight inspections after
12 of 24 shuttle missions to date had uncovered clear evidence of significant
O-ring erosion, and the sensitive seals were not certified to fly in weather
below 53 degrees Fahrenheit (11.5 degrees Celsius).
While the Challenger crew
slept, Thiokol engineers unanimously recommended a launch postponement
because they feared the O-rings might allow hot gases to leak in temperatures
that ultimately dipped to 36 degrees Fahrenheit (2.2 degrees Celsius) at
launch time.
Mid-level managers from Marshall,
however, protested strongly, saying Thiokol engineers – in spite of the
past history of O-ring problems -- did not have enough data to support
their concerns.
Bowing to pressure, Thiokol
engineers eventually reversed their recommendation and approved plans to
proceed with launch. Higher-level NASA managers, meanwhile, were not informed
of the late-night debate and the Challenger crew met its fate.
The presidential commission
that investigated the accident found that there was a "serious flaw" in
the decision-making process leading up to the Challenger launch.
NASA failed to flag rising
concerns about O-ring problems, waived its own strict launch rules and
allowed schedule pressure to override flight safety issues, the commission
found.
Things are different now,
especially when technical issues crop up with so-called "Criticality 1"
systems – those systems whose failure would lead to the loss of a shuttle
and its astronaut crew.
"Now the whole discussion
revolves around the technical merit [of an issue], the pros and cons in
terms of flight safety, and then a decision is made," said former NASA
launch director Bob Sieck, who also is a member of the Aerospace Safety
Advisory Panel. "Schedule ramifications are kind of an after-the-fact thing."
The decision to delay the
Atlantis flight is just one case in point. Another was the decision to
ground the agency’s shuttle fleet when dangerous orbiter wiring flaws were
uncovered in 1999.
"The sensitivity to safety
is as high as I’ve ever seen it," said Sieck, who joined NASA in 1963 and
spent more than a quarter-century with the agency. "People are very sensitive
to the criticality of what they do and what they work on, and they perform
accordingly."
That, Dittemore said, is
just the way NASA is going to do business in a day and age when the agency
can ill-afford another Challenger-type disaster.
"I guard against this phenomenon
of 'go-fever’ like it was the plague," Dittemore said.
"Schedule is schedule and
it does not compete with safety. We will roll back from the pad – as we
did in this case – and we will take whatever other steps are necessary
to preserve the integrity of the [shuttles] and the safety of both those
who fly the vehicle and process it on the ground," the shuttle program
manager added.
"That’s just laws to live
by."
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