NASA Pinpoints Tile Damage
As a Likely Cause of Disaster
By J. LYNN LUNSFORD and ANDY PASZTOR
Staff Reporters of THE WALL STREET JOURNAL
NASA officials said it is increasingly likely that the "root cause" of the space shuttle
Columbia's disintegration Saturday was damage to the craft's heat-resistant tiles shortly after
takeoff, an incident that NASA had initially decided didn't pose a threat to the flight.
NASA also said that the "real key in the puzzle" may be locating parts that may have ripped off
the space shuttle perhaps half a continent before Columbia broke up in the skies above Texas.
In their most definitive description yet of the sequence of events that caused the crash,
investigators said they are becoming more convinced that the Columbia began to malfunction
as it zoomed over California at more than 42 miles in the air. All seven astronauts aboard were
killed.
About eight minutes before the orbiter disintegrated, temperature sensors inside the left wheel
began to register abnormally high heat. As the red-hot craft crossed over Texas seven minutes
later, enough parts had apparently peeled away to create more drag on the left wing than the
right and causing the shuttle to become less aerodynamic.
Ron Dittemore, shuttle program manager, said at a news conference Monday that the shuttle's
autopilot system attempted to keep the orbiter on course, but "it appears that we were losing
ground." Not long after that point, he added, "we lost contact."
In their effort to unravel the disaster, Mr. Dittemore acknowledged that he and his team also
are re-examining their initial conclusions about the likely damage caused by what was believed
to be a 20-inch long chunk of foam insulation that struck the left side of Columbia barely a
minute after blastoff. Based on a film of the launch, the space agency believes that insulation
from the orbiter's external fuel tank dislodged and smacked into the underside of the shuttle's
left wing.
Officials said that after the shuttle was in orbit, engineers spent 12 days of the mission trying
to assess the safety consequences of the incident. They studied frame-by-frame images from
a video taken of the shuttle's ascent, and determined that when the foam hit the wing, it
appeared to vaporize. During the review, one internal NASA report described the formation of
a "white cloud" after the impact. But at the time, agency engineers and administrators
concluded that the impact didn't pose any significant safety problem.
"We thought we would get some minor structural damage" in a localized area, said Mike
Kostelnik, a deputy associate administrator for NASA.
But now, one possibility investigators are looking into is that, in addition to the foam, the
orbiter might have been hit by ice, according to one person familiar with the investigation. The
ice could have stuck to the insulation, or possibly formed elsewhere on the vehicle and gone
undetected before launch. Such extra weight likely would have increased the extent of the
damage to Columbia.
Without saying whether he believes ice was a factor, Mr. Dittemore stressed that NASA
officials "want to know if we made any mistakes."
In the past, Mr. Dittemore said, such accidental hits had merely "taken some of the coating
off" or "gouged out some of the tile," without allowing the underlying structure to be damaged
by re-entry temperatures as high as 3,000 degrees Fahrenheit.
But in light of the shuttle's disintegration, "we're making the assumption from the start that the external tank was the root cause
of the problem," Mr. Dittemore said. "That's a fairly drastic assumption, and it's sobering."
The latest developments highlight the dilemma flight controllers faced after learning of the possible damage to the heat shield,
which has long been considered an Achilles' heel for the shuttle. About 20,000 of the tiles, made of a chalky material that is
sealed in an eggshell-thin black ceramic coating, cover the nose, wings and tail of the vehicle.
But because the shuttle was already in orbit when controllers learned about the possible damage, there was little that could have
been done to help the astronauts. The shuttle carried space suits to be used in the event of an unplanned space walk, but there
was no way for the astronauts to inspect the bottom of the orbiter, nor has anybody found a reliable way to make repairs in
microgravity, NASA has said.
Even if NASA engineers had wanted more time to further analyze safety issues on the Columbia, the orbiter didn't have enough
food or other essentials to stay in orbit for additional days or weeks. Furthermore, there was no docking mechanism onboard to
try to link up with International Space Station.
Reflecting NASA's deep-seated safety concerns about the fragility of the tiles, the agency years ago began working to develop
stronger variants better able to resist damage from flying debris. Indeed, during Columbia's initial flight 22 years ago NASA asked
the Pentagon to help it determine the extent of tile damage after that launch.
Since then, NASA has improved the adhesives and backing materials used. Well before Columbia's launch, NASA also had started
a special review of why foam insulation from the fuel tank was prone to fall off. Applied by a computer-controlled spray gun, the
insulation starts out as foam and then hardens. Ten different types of insulation manufactured by a handful of companies are
used, depending on the area to be treated. The insulation is designed to prevent ice buildup and protect the tank from engine and
aerodynamic heating. |
