[sarex] Smoking Out Space Fires: ON THE ISS
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Fri Oct 6 14:12:35 PDT 2006
SUBMITTED BY ARTHUR N1ORC - AMSAT AC #31468
Smoking Out Space Fires: NASA Study Helps Prevent Fires in Space
If you've ever burned your dinner, you know how startling a smoke alarm
can be. Now, imagine you're 220 miles away from Earth in an orbiting lab
when the alarm sounds.
Fires are no laughing matter on Earth, but in space they could be even
"If a chair is on fire in your home, you have time to get out. In a
spacecraft, you don't," said NASA scientist Dr. David Urban. "You have
to detect smoke in an early pre-fire state, so you can stop it before it
This may not sound like a major challenge. After all, household smoke
detectors are mass produced and inexpensive. But detecting smoke in
space isn't quite so simple.
Smoke detectors work by looking for particles in the air that are about
the same size as the particles normally found in smoke. However, a 1996
NASA Glenn study showed that smoke particles in space are bigger than
those on Earth.
"Smoke particles form differently in microgravity than they do on the
ground," said William Sheredy, project manager for the Smoke Aerosol
Measurement Experiment (SAME). "When smoke is created in microgravity,
the particles have more time to gather together, producing larger
particles or particle chains than in normal gravity."
So far, nobody knows exactly how big those particles are. That's why the
NASA Glenn team created SAME. This space station experiment will burn
samples of materials normally found in space -- like Teflon, silicon,
cellulose and Kapton -- and then measure the size of the particles in
the smoke. Engineers will use this information to design the next
generation of spacecraft smoke detectors.
As NASA often does, the team used several commercial parts to build the
experiment. One of those parts, the P-Trak, was made by Minnesota
company TSI. Designed to measure air quality, this small handheld device
is capable of counting individual smoke particles. It's also the perfect
size and weight for a space station experiment. There's just one catch:
It wasn't designed for space.
P-Trak works by passing air through a heated chamber of vaporous
alcohol. When the air is cooled, the alcohol condenses around dust
particles much like water condenses on a cold glass. This makes the
particles large enough that an optical sensor can detect them as they
scatter light from a laser beam.
"We were concerned because gravity assists in the circulation of the
alcohol inside the device," Sheredy said.
"We weren't sure it would work properly in the absence of gravity."
So the scientists modified the device by carving tiny grooves inside its
chambers to improve the flow of alcohol in microgravity. Of course, the
scientific method requires every theory to be tested, and this
experiment was no exception.
Before they could use the device in SAME, the team had to be sure the
modification would work. To do so, they created another space station
experiment called the Dust and Aerosol Measurement Feasibility Test
(DAFT), to test the modified P-Trak.
In September, astronaut and Expedition 13 Flight Engineer Jeff Williams
operated DAFT on the station. Urban, Sheredy and other DAFT team members
watched in real time as Williams called in the recordings to Payload
Communications. The results showed that the commercial particle counter
works in space.
"It was really exciting. For people who work on projects like we do,
days like this are highlights in our careers," said Sheredy. "From
beginning to end, DAFT took about 3.5 years, and it all came down to
about six hours of operation."
Those crucial six hours brought the team one step closer to
understanding the nature of space smoke and improving NASA's detectors.
They look forward to another career highlight next summer when their
primary experiment, SAME, is scheduled to travel to the station aboard
the space shuttle.
FOR PHOTOS GO
Jan Wittry (SGT, Inc.)
NASA's Glenn Research Center
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