NASA Science News home |
|
May 12, 2000 -- The forms
of flames on Earth are familiar to everyone. We all know what
a burning match, candle, fireplace or blowtorch look like --
or a burning building, or rocket ignition blast. The presence
of gravity and the effects of air or gas movement, plus the type
of fuel and oxidant, determine everything from a flame's shape
and temperature to burn rate, burn pattern, soot production and
deposition and how fast it will or won't be extinguished.
"The absence of gravity's effects on convection aboard the Space Shuttle, a space station or other space vehicle makes flames behave in ways that can be either beneficial -- as a test bed for research -- or very dangerous in the case of a fire in materials, chemicals or electrical devices. It is vital to know what makes flames start and stop in low gravity, and how flames behave while burning. The safety of NASA's space crews and vehicles can depend on our knowledge of combustion in space." Watching the Flame Go 'Round Recently, Dr. Nayagam and Dr. Forman Williams of the University
of California at San Diego, a co-investigator in NASA/GRC's microgravity
combustion science program, came upon some startling discoveries
about flames on Earth that could help scientists understand how
flames behave in microgravity. Right: Flames on top of a disk slowly spinning in a clockwise
direction burn in a spiral headed counterclockwise. Vedha Nayagam
and Forman Williams are studying this phenomenon, which occurs
both on Earth and in microgravity, in the hopes of fully explaining
the pattern with basic physics principles. "Under slow spin conditions ... just before circular
flames extinguish, [the flames] break symmetry -- and spirals
appear in the center hole of the flames and propagate outwards
in a spiral instead of in a circular wave front," he explained. Nayagam says it's an advantage to be able to generate these
flames in the lab under normal gravity, where it is easier and
less expensive to study them than on the Space Shuttle. The investigators
plan to conduct further tests with spiral flames on board the
Johnson Space Flight Center's KC-135, which can create brief
microgravity conditions in parabolic flight.
"Understanding these surprising phenomenon may enable
scientists to predict flame extinction and to help mitigate fire
risks on Earth and in microgravity," states Dr. Nayagam.
"The initial and on-going basic reason for NASA's combustion
studies is to learn about spacecraft fire safety. We need to
answer questions such as: what is the worst condition for fire
in a microgravity environment, and under what conditions a fire
will increase its burn rate or be extinguished. Our goals include
learning under what conditions materials in a spacecraft will
or won't support fire." Readers can learn more about flames in space at the Microgravity Combustion Research home page. |
Web Links |
Rotating
Spiral Edge Flames in von Karman Swirling Flows -- by V.
Nayagam and F. A. Williams. Physical Review Letters -- January
17, 2000 -- Volume 84, Issue 3, pp. 479-482 Fires in Space - basic information
about combustion in low gravity from microgravity.com |
Join our growing list of subscribers - sign up for our express news delivery and you will receive a mail message every time we post a new story!!!
|