[meteorite-list] No Sign Nature Downed Columbia

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:22:34 2004
Message-ID: <200306051539.IAA26817_at_zagami.jpl.nasa.gov>

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2003/06/05/MN294953.DTL

No sign nature downed Columbia

Analysis of sounds kills theory that lightning hit space shuttle

Sabin Russell
San Francisco Chronicle
June 5, 2003

There were no lightning strikes and no meteorite hits as the space shuttle
Columbia made its doomed re-entry over the western United States,
according to an analysis of sounds of the shuttle's fiery return, caught by a
network of extraordinary electronic ears.

A team of experts in the science of low-frequency sound wave detection
completed their analysis for the Defense Department two months ago and
made the study public Wednesday. Inside NASA, their report helped put to
rest theories that an electrical discharge or a collision with a meteorite
might have played a role in the tragedy.

"There had been a suggestion of a high-altitude lightning strike," said
study leader Henry Bass, director of the National Center for Physical
Acoustics at the University of Mississippi. "But had that been the case, we
would have seen other data. There were no such data."

Fueling speculation that some sort of electrical strike might have damaged
Columbia was a photograph taken by an amateur astronomer in San
Francisco. It appeared to show a bolt of electricity corkscrewing toward
Columbia. The image was taken when the shuttle was above Northern
California.

Although NASA has declined requests for a copy of its analysis of the
image, spokeswoman Patricia Brach has told The Chronicle that investigators
concluded that it was probably created by accidental camera movement. "At
this time, it appears to be camera jiggle," she said.

Neither NASA nor the San Francisco photographer has released the
photograph, which was described in February by Chronicle reporters who
were shown it before it was shipped to Houston for analysis.

NASA officials took the photograph seriously enough that they enlisted
experts in low-frequency sound waves, or "infrasound," to look for
evidence of a faint thunderclap at the time the photograph was taken. The
unique quality of infrasound is that it carries for thousands of miles.
Infrasonic arrays can detect volcanoes erupting, the hiss of meteors,
lightning strikes and the sound of space shuttles returning home.

Although the scientists did not find evidence of a celestial thunderclap in
the recording of Columbia's descent, there were some curious findings. The
network of 10 infrasonic stations -- spread from Hawaii to Texas --
picked up an unusual burst of sound as the shuttle passed over the
California-Nevada border. The sound occurred at the same moment that a
photographer near Reno snapped pictures showing a brightening of the
shuttle's plasma trail.

Too little is known about the soundtracks of shuttle re-entries to make
much of the spike in the sound signal, but Bass said it was most likely
caused when Columbia fired its rockets to change its angle of attack,
perhaps in a computer-guided attempt to compensate for the increasing
drag on its damaged left wing.

"When you turn a little, you can get a much-enhanced shock wave," Bass
explained, during a telephone press conference. A variety of S-shaped turns
are executed during a shuttle re-entry to reduce speed, but no other
maneuvers of this sort triggered a spike of low-frequency sound.

Columbia's final pass over the Pacific and the western United States ended
in a shower of debris over thousands of square miles of Texas and Louisiana.
Investigators believe a piece of foam insulation from a fuel tank knocked a
hole in the leading edge of Columbia's left wing during launch that, two
weeks later, caused the doomed spaceship to disintegrate during re-entry.

Although the destruction of Columbia occurred in a matter of minutes, the
infrasound detectors picked up signals for nearly an hour, as distant sounds
traveling hundreds of miles -- and blown about by winds -- finally
reached the detectors. As the shuttle came apart over Texas, the single wave
of sound broke into hundreds of smaller signals as each piece of debris
created its own supersonic wake.

Although the thrust of the infrasound report is that nothing unexpected
was revealed by infrasound signals, other scientists are not so certain. In a
separate report, NASA physicist Alfred Bedard, of the NOAA
Environmental Technology Laboratory in Boulder, Colo., said Columbia's
infrasound signature did show subtle differences from those of other
shuttles re-entries he had tracked.

Bedard, an expert in detecting the infrasound signatures produced by high
atmospheric lightning known as sprites, agreed that there were no sounds
of sprites on the tapes. However, he said that Columbia's trailing wake
contained infrasonic "impulses" he'd not detected before. "These surges, to
me, were unusual," Bedard said.

He said they could have been caused by the shedding of debris, or by the
rapid firing of thruster rockets as Columbia's computers sought to keep the
orbiter stable. His report recommends further study, to compare those
signals more precisely to events tracked in the shuttle's flight data
recorder.

E-mail Sabin Russell at srussell_at_sfchronicle.com.
Received on Thu 05 Jun 2003 11:39:17 AM PDT