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NASA Science News for January 31, 2003

A Flame Ball Named Kelly
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Flame balls onboard the space shuttle Columbia (STS-107) have been
doing some strange and wonderful things. 

January 31, 2003:  They're creatures of space: tiny flames that curl
into balls and flit around like UFOs. They burn using almost no fuel
at all, dim and often hard to see. Yet they have plenty of
personality.

"I'm calling this one] Howard," deadpanned astronaut Dave Brown
onboard the space shuttle Columbia (STS-107) this week. He had been
filming the tiny flames for some time, watching them roam around their 
test chamber in a lifelike search of food (fuel), when the idea popped 
into his head. These flame balls needed names. 

"After that everyone started naming them," says USC engineering
professor Paul Ronney who designed the experiment. "It was fun. It
also helped us keep track of some of the strange things we saw." For
example, two flame balls flew around in a spiral pattern like DNA.
"We called them Crick and Watson."

It's more than just fun, though. These flame ball experiments--called
SOFBALL, short for Structure of Flame Balls at Low Lewis number--are
serious investigations into the physics of fire. 

Unlike flames on Earth, which have a tear drop shape caused by air
rising in a gravitational field, flames in space break apart into
spheres a few millimeters in diameter. A typical floating flame ball
produces 1 to 2 watts of thermal power--much less than, say, a 50 watt 
birthday candle. "We created some flame balls on STS-107 that emitted 
only 0.5 watts--a record low," he says. 

Flame balls are "lean" burners; they don't need much fuel to keep
going. Engineers would love to duplicate their efficiency in the
engines of automobiles, "but first we have to understand how flame
balls work," says Ronney. 

That's the goal of SOFBALL.

SOFBALL is a chamber about the size of an office trash can filled with 
combustible gases: "a little bit of hydrogen or methane (the fuel), 
some oxygen (the oxidant), and a lot of inert gas (e.g., helium or 
nitrogen) to dilute the mixture until it is barely flammable," says 
Ronney. The experiment rides in the shuttle's cargo bay inside a rack 
called the Combustion Module. Astronauts simply press a button to 
spark the mixture and voila ... flame balls. Their temperature, 
brightness, heat loss, and the composition of their gaseous byproducts 
are all monitored by built-in instruments. SOFBALL was built and 
tested at NASA's Glenn Research Center under the guidance of project 
scientist Karen Weiland and project manager Ann Over.

This is SOFBALL's second flight; the first was in 1997, also onboard
Columbia (STS-83). In those days the experiment ran for only 8
minutes. "We didn't think flame balls could last more than a few
minutes," explains Ronney, "but we were wrong. Many of them were still 
burning when SOFBALL's control computer automatically ended the test. 
We needed more time." 

So, during STS-107, SOFBALL has operated for periods as long as three
hours. And "we've seen some extraordinary things," says Ronney. 

Crick and Watson are examples. Ronney says he has no idea what would
make a flame ball fly around in a spiral. "Flame balls move for two
reasons," he explains. "First, when they exhaust the fuel in their
vicinity, they drift toward regions with more. They follow the fuel
like a little organism. Second, they can drift due to slight
accelerations of the shuttle." Neither of these effects would produce
a corkscrew flight path. 

Howard is another example of something Ronney had never seen before.
"Howard was suicidal," he says. Instead of following the fuel like a
flame ball should, Howard headed straight for the walls of the
chamber--a fuel-poor region. "He promptly went out. We saw several
more flame balls like this, too." It's another mystery. 

The SOFBALL experiment also produced the biggest and the smallest
flame balls ever recorded--ranging from 2 mm to 15 mm across. "We
named one of the biggest ones 'Zeldovich' after the Russian physicist
who predicted flame balls in 1944." A well-meaning astronaut named one 
of the flame balls 'Paul Ronney,' "but it turned out to be small and 
short-lived--a wimp," Ronney laughed. 

Oscillating flame balls were another first. "About 15 years ago John
Buckmaster at the University of Illinois and Guy Joulin of CNRS in
Poitiers, France, predicted that flame balls about to run out of fuel
should oscillate. You've probably seen something like this in low
burning candle flames, which jump up and down in a rhythmic pattern
just before they go out. We had never observed these oscillations in
flame balls before, but now we have--in two flame balls named
Buckmaster and Joulin." The period and duration of the pulsations
reveal a great deal about the inner workings of flame balls, adds
Ronney. It's a very important result. 

Ronney's favorite flame ball, though, is Kelly. "Before the mission
began I said I wanted to send a flame ball around the world. Kelly
almost made it." The shuttle circles Earth once every 90 minutes;
Kelly burned for 81 minutes--the longest-lasting flame ball ever
recorded. 

"Kelly's experience is a fascinating example of group dynamics among
flame balls," says Ronney. "She was created, one of nine flame balls,
in a gaseous mixture of hydrogen, oxygen and sulfur hexaflouride (the
inert filler). All the others began drifting around the chamber,
looking for food, competing with one other, while Kelly remained
motionless at the center. Before long, the others were exhausted; they 
had drifted too close to the walls and winked out. Kelly was left all 
alone with a chamber full of fuel." 

"It pays to be patient," notes Ronney. And he should know. Ronney
discovered flame balls in 1984 in a drop tower at NASA-Glenn in Ohio
where the weightless lifetime of a flame ball is only a few seconds.
He's been waiting almost 20 years for data like this.... 

There's a sign in Ronney's office: When the Gods want to punish you
they answer your prayers. "It's going to take us years to analyze all
these results!" 

He's delighted.

Editor's note: Astronauts ignited and filmed 55 flame balls during the 
STS-107 mission (which is still ongoing as this story is being
published); 33 of them received names after trend-setter Dave Brown
christened one of his "Howard." 

Credits & Contacts
Author: Dr. Tony Phillips 
Responsible NASA official: Ron Koczor 
Production Editor: Dr. Tony Phillips 
Curator: Bryan Walls 
Media Relations: Steve Roy

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