[meteorite-list] NASA Considering Space Hit In Columbia Accident

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:25 2004
Message-ID: <200302051626.IAA02468_at_zagami.jpl.nasa.gov>

http://www.latimes.com/news/nationworld/nation/la-na-nasa5feb05,0,3696741.story?coll=la%2Dhome%2Dheadlines

NASA Considering Space Hit

Investigators say Columbia may have been struck by a meteorite or man-made
debris while in orbit.

By Scott Gold and Ralph Vartabedian
Los Angeles Times
February 5, 2003

HOUSTON -- NASA investigators remain unconvinced that the chunk of foam
insulation that struck Columbia's heat-resistant tiles on takeoff led to its
destruction, and also are now considering the possibility the craft was
struck by space debris while in orbit, the agency's chief flight director
said Tuesday.

"Did we take some hit?" Milt Heflin, the flight director, said in an
interview Tuesday at Johnson Space Center. "That's a possibility. Something
was breached."

NASA investigators have developed what has become known inside Johnson Space
Center as a "fault tree" - a list of potential mishaps and flaws that might
have caused Columbia to break apart Saturday morning over East and central
Texas.

The list, aimed at finding the cause of what NASA terms the "thermal event"
that destroyed the shuttle, includes several theories. Although the current
investigation focuses on several scenarios related to tile damage, some
analysts also have questioned whether faulty wiring or corrosion could have
played a role.

Nonetheless, the prime suspect remains the piece of foam insulation that
fell off the external tank during the Jan. 16 liftoff, possibly damaging the
protective tiles.

Tile vulnerability has been an object of warnings for years. One study
prepared for NASA nearly a decade ago warned that insulation and ice debris
could result in enough damage to doom the orbiter during reentry.

"We estimated that [the loss of a shuttle] was a possibility," said Paul
Fischbeck of Carnegie Mellon University in Pittsburgh, one of the authors.

Despite warnings that the shuttle could be endangered if debris struck its
underbelly during liftoff, some engineers do not believe that any scenario
would have been destructive enough to cause Columbia to crash.

NASA's computers have calculated the potential damage caused by the foam
insulation. Under two worst-case scenarios, NASA investigators say, the
insulation either would have destroyed a single heat-resistant tile near the
landing gear door or caused damage to a 32-by-7-inch patch of tiles along
the shuttle fuselage.

That means the spacecraft's tiles - 24,000 ceramic pieces that have been
problematic from the beginning of the shuttle program - could have been
damaged some other way, Heflin said, possibly by space junk or a tiny
meteorite. NASA engineers say they are considering the possibility that a
small piece of space debris could have grazed the shuttle, damaging or
loosening tiles just enough to start a chain reaction once the craft started
roaring through the atmosphere.

The ceramic tiles act as a protective armor around the body of the space
shuttle, protecting it against the intense heat of reentry through the
atmosphere. Although many tiles are damaged or knocked off during missions,
missing tiles in a particularly vulnerable portion of the spacecraft, such
as at the leading edge of its wings, could imperil its ability to fly.

The skepticism of some engineers and attempts to broaden the list of
suspects failed to shift attention from insulation debris Tuesday as more
reports documenting past warnings emerged.

"The foam insulation falling off the external tank could certainly damage
tiles," Fischbeck said in a telephone interview.

The 1994 report he co-authored with Elisabeth Pate-Cornell of Stanford
University specifically cited concerns about Columbia, noting that tiles
"were put in place under severe schedule constraints, which may have
affected the quality of the work."

Columbia was the first orbiter built, and the report found problems with
tile adhesion and trapped water. Fischbeck and Pate-Cornell advised that the
tiles be waterproofed. The report did not indicate whether those
recommendations were followed, but Fischbeck said the agency took the
recommendations seriously and made improvements.

NASA officials have said in news briefings that a 20-inch chunk of foam,
weighing about 2.67 pounds, was videotaped falling off the external tank and
striking the underside of Columbia's left wing about 80 seconds after
liftoff. That represented the largest piece of debris ever known to have
fallen off the tank. At 80 seconds into flight, the orbiter was nearing a
speed of 2,000 mph, meaning the foam carried substantial energy into the
impact and could have caused serious tile damage, according to Fischbeck.

The 1994 report warned NASA of several scenarios that could cause
catastrophic safety problems, including the potential for a "zipper effect"
where the loss of a single tile would, in turn, cause adjacent tile losses
until opening a large unprotected gap. Such exposure could make vital areas
of the shuttle - such as critical hydraulic lines, computers or fuel tanks -
vulnerable to destructive heat, the report said.

After the report was issued, Fischbeck said NASA took steps to sharply
reduce foam debris. The experts also urged NASA to find ways to improve tile
safety, despite budget cuts.

"NASA must find ways of being cost-effective, because it simply cannot
afford financially or politically to lose another orbiter," the report
cautioned.

Heflin said his engineers have no hard evidence Columbia was struck by a
piece of space junk or a space pebble, known as a micrometeor. What's more,
NASA takes great care during missions to avoid the man-made objects, from
ejected payload shrouds to tools left behind by astronauts after spacewalks,
that are in constant orbit. By some estimates, there are more than a million
objects within 1,200 miles of the Earth's surface.

Heflin also pointed out that the space debris theory has not supplanted the
foam insulation theory, but has been placed alongside it on the "fault
tree."

Analysts inside and outside the space program are torn over the possibility
that space debris is to blame. There are several problems with the theory.

First, the Air Force and NASA together perform a comprehensive analysis of a
shuttle's projected path before each mission to ensure that it is not struck
by debris, said Howard Sands, a former NASA official who worked as a
contracting officer for space shuttle logistics before he retired in 1986.
The Air Force has the ability to pinpoint the location of space debris that
is just centimeters in diameter, and would have warned NASA about the
dangers of debris large enough to damage it.

Second, there are "clean" and "dirty" levels of orbit above Earth. The space
shuttle typically coasts along at 15,000 mph in one of the relatively clean
levels, close to the atmosphere. At that level, much of the debris left
behind by earlier space flights or defunct satellites falls into the
atmosphere and burns up before it can do damage.

"Up higher, things can stay around for hundreds, maybe thousands of years,"
said a Boeing engineer who works on the international space station, which
orbits in a higher and much "dirtier" path. The engineer spoke on the
condition of anonymity. "Down where the shuttle is, things are kind of
getting sucked into the Earth's orbit like there's a big vacuum cleaner," he
said.

Finally, if something struck the shuttle with enough force to ultimately
bring it down, many analysts say NASA, its crew and the craft's computers
would have known instantly. NASA's test facility in White Sands, N.M.,
recently conducted a study of the potential impact of space debris. The
conclusion: A piece of plastic the size of a walnut could tear a 5-inch-wide
hole through aluminum as thick as the Los Angeles telephone book. In other
words, one analyst said Tuesday, if the shuttle struck something, "everybody
would know. It would be loud."

"That stuff moves so fast relative to the shuttle," said the analyst,
speaking on condition of anonymity.

On the other hand, "there is a lot of debris up there," said William Ailor,
president of Aerospace Corp., a nonprofit group in El Segundo that provides
technical support to the Air Force and studies orbital matter. After all,
Ailor said, "we've been in space for 40 years."

There are enough pieces of debris in space that some scientists have
proposed a variety of remedies. Some hope to install robotic arms on
spacecraft that can grab old satellites and pull them into orbits where they
can't do any damage.

NASA has had to adjust the flight path of space shuttles at least eight
times to avoid large pieces of debris, Ailor said. Most of the debris is
found at extremely high levels of orbit, where satellites are kept - more
than 250 miles higher than the space shuttle typically flies. Studies show
that all but 9,000 of the pieces are smaller than a tennis ball, including
thousands of tiny particles left behind by solid rocket motors.

In addition, there are countless micrometeorites, some of them smaller than
the diameter of a strand of hair, Ailor said. Most of them are so tiny that
they can do no damage to a spacecraft as large as a commercial airplane. One
study showed that a craft that had been in space for more than five years
was struck by these particles more than 30,000 times, with no ill effect.

Still, NASA has discovered pockmarks on at least two shuttle windshields
after the crafts returned safely, Sands said, possibly because of collisions
with that matter in space. A speck of paint once chipped the windshield of
the space shuttle Challenger during a mission completed before it exploded
in 1986. Some have estimated that the speck was traveling 20 times faster
than a bullet travels on Earth.

That sort of matter could weigh just enough to damage a thermal tile, Ailor
said. And, Sands added, it's possible that a piece of space debris could
have broken off a satellite or a larger piece of space trash during
Columbia's 16-day mission, and didn't show up on engineers' maps until it
was too late. "It could happen," Sands said. "It is a possibility."

Meanwhile, NASA expanded its search Tuesday for Columbia's wreckage by
several states.

After scouring the ground for clues in Texas and Louisiana - and discounting
reports that the shuttle may have begun breaking up farther west - NASA sent
investigators to California and Arizona when credible reports surfaced that
pieces of Columbia may have landed there. If the debris proves to be from
the shuttle, it may offer an early glimpse of what was happening before
Columbia broke up over Texas.

Michael Kostelnik, the high-ranking NASA official responsible for the
shuttle and space station programs, said what may prove to be the wreckage
of the shuttle's main engines has been located in Louisiana. Heavy pieces,
like the engines, would travel farther after the spaceship broke up.

Kostelnik said he did not know the location of the reported debris in
California and Arizona.

"It's not clear what the material is," Kostelnik added. "We have had some
e-mail correspondence that potentially looks like it could be either [tiles]
or potentially wing material. If it is wing material, obviously that would
be very important to the investigation.

"Certainly something that early in the event is most important," Kostelnik
said.

NASA's main priority for now is to recover the remains of the astronauts'
bodies, and thereafter to hunt for the most important pieces of wreckage.
The crew compartment has not been recovered in any identifiable form,
Kostelnik said, though pieces of it may be in official custody.

Times staff writers Ricardo Alonso-Zaldivar in Washington and Eric Malnic in
Houston and Nona Yates in Los Angeles contributed to this report.
Received on Wed 05 Feb 2003 11:26:30 AM PST