Making fire was a fundamental evolutionary step for our civilization, so you'd think that we'd totally understand the phenomenon inside and out by now. But, as experiments on the International Space Station (ISS) are proving, fire is a very different and mysterious creature when it burns in a microgravity environment.
Usually, flames in the presence of gravity (i.e. on Earth) form under complex chemical reactions. But gravity ensures that the flame on a candle, say, forms a ‘droplet' shape - hot air rises, pulling in cool air behind it, shaping the flame. But in the absence a strong gravitational field - like the microgravity environment in the ISS - fire transforms into a very alien configuration.
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"In microgravity, flames burn differently - they form little spheres," said Forman A. Williams, a professor of physics at UC San Diego, in a fascinating NASA Science article published today (June 18).
During experiments on the orbiting outpost, these small burning spheres were created inside the Flame Extinguishment-2 (FLEX-2) instrument using the highly flammable liquid hydrocarbon heptane. When ignited, a hot flame surrounded the droplet, burning at a temperature of between 1,500K and 2,000K.