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Experts discount 'sprite' theory
Shuttle wasn't
flying above thunderstorm
Matthew B. Stannard, Chronicle Staff
Writer
Saturday, February 8,
2003
©2003 San
Francisco Chronicle | Feedback
URL: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2003/02/08/MN117739.DTL
NASA officials said Friday they have asked experts in upper-atmosphere
electric phenomena whether it is possible for such effects to occur at the
altitude and weather conditions that the shuttle was flying through before it
disintegrated.
But they said that so far they have found nothing in their investigation to
indicate that the shuttle encountered such phenomena on re-entry. "There is
nothing in the data stream . . . that would cause any concern on our part,"
said Ron Dittemore, NASA's shuttle program manager.
Independent scientists also said that speculation that ghostly
electromagnetic events -- dubbed sprites, blue jets and elves -- might have
triggered the space shuttle disaster conflicts with current theories of how
those phenomena occur.
They can occur over large thunderstorms, but no major thunderstorms were
raging in the shuttle's vicinity as it passed over the far Western United
States, including Northern California, early last Saturday, the researchers
said.
Still, the same scientists declined to totally reject the "sprites" thesis.
They stress that it is simply too early to know the true cause of the
accident,
partly because the shuttle Columbia began breaking up in a region of
Earth's upper atmosphere about which researchers know comparatively little.
On Friday, a Chronicle story reported that federal investigators are
reviewing records from ultrasensitive instruments that might have detected a
faint thunderclap at the same time a photograph taken by a San Francisco
amateur astronomer appears to show a purplish bolt of lightning strike the
shuttle.
Asked about the electromagnetic phenomena, Ron Dittemore, the NASA shuttle
program manager, said in a news conference Friday: "I really have no idea
whether we had any static electricity, whether we had any electrical
discharge.
"We are asking experts in the field of atmospheric science if those events
are even possible, especially at the altitude that we were flying -- greater
than 200,000 feet," and "especially in the relatively clear skies that we were
flying on last Saturday," he said.
Dittemore also said that NASA has received, but still is analyzing the
amateur astronomer's photo. (The astronomer has refused to release it to news
media.)
Investigators will be reviewing photos of the Columbia re-entry and
comparing them to similar photos from past shuttle missions, Dittemore said.
He warned against drawing conclusions from photos, videos or other data at
this stage.
"You want to draw conclusions as quickly as you can based on the
information," he said. "You go down that merry path of making a judgment, or a
rush to judgment, and you will be fooled."
Based on a reporter's description of the photo, Walter Lyons, a leading
sprites authority, said that the object "is definitely not a sprite or a blue
jet." In photographs, Lyons noted, sprites resemble somewhat spidery glows
flickering over the anvil-shaped tops of thunderstorms.
Also, weather conditions didn't jibe with traditional theories of sprites
and their cousins, dubbed blue jets and elves. "There were showers north of
(the shuttle's flyover path)," but there were no thunderstorms in the area,
Lyons said.
"There's just not the meteorology to support (the theory of a) sprite or
blue jet. It's probably just an artifact of the (photographic) image," Lyons
said in a phone interview. "All bets are off if the image turns out to be an
artifact."
"The fact is that until we see the picture, we're all just flapping our
wings," said Lyons, of FMA Research Inc. in Fort Collins, Colo., who has done
contract work for NASA and other scientific agencies.
Martin Uman, one of the world's leading experts on lightning and other
forms of atmospheric electricity, said sprites tend to occur over
exceptionally large systems of thunderstorms, about 40 to 50 miles wide. There
is no evidence that sprites occur independently of thunderstorms, Uman said.
Also, despite their famed, creepy-looking "arms" and "tentacles," sprites
don't typically concentrate energy into extremely narrow, hot channels like
lightning bolts, said Uman, who works at the University of Florida's Lightning
Research Laboratory.
Sprites' charge is "spread out over a kilometer or something -- it's a
really diffuse discharge," Uman said. "Whether a big metal body up there like
the shuttle could focus some of this current flowing through the air is a
question."
At the same time, Uman added, "we don't understand that much about that
part of the atmosphere." The shuttle was about 40 miles above Earth as it
passed over California. Sprites can occur across a vast atmospheric gulf
ranging from the tops of thunderheads usually many thousands of feet high to
approximately 50 miles.
The Associated Press reported that researchers at NASA's John F. Kennedy
Space Center in Florida raised concerns in a 2002 report that shuttles could
encounter electromagnetic phenomena or ice crystals from the highest clouds on
re-entry. The report estimated a 1-in-100 likelihood of a shuttle flying
through a sprite, blue jet or elf during re-entry over a thunderstorm.
However, "expert panels so far have concluded that sprites, blue jets and
elves do not pose a hazard to the space shuttle, which is designed to
withstand a harsh electrical environment," said the report. The Kennedy Space
Center researchers sent the report to the American Institute of Aeronautics
and Astronautics in Reston, Va.
Chronicle science writer Keay Davidson contributed to this report. /
E-mail Matthew B. Stannard at [EMAIL PROTECTED].
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