The wonder of fire without gravity


EXCERPT: . . . To study combustion on the ISS, and before that, the Space Shuttles, astronauts have set fire to a variety of materials and observed how this distinctly earthly phenomenon unfolds in microgravity. And they love doing it. “They get very excited,” Paul Ferkul, a scientist at the Universities Space Research Association, told me recently. “They’re all very glad to burn stuff.”

[...] In space, a flame is shaped like a sphere instead of a teardrop, and it doesn’t flicker. It just hovers, a small, ghostly orb, until it goes out. Such orbs are called “flame balls,” a term that is both extremely accurate and delightfully deranged. “It’s kind of mesmerizing to see this burning without gravity present,” Ferkul said.

Ferkul and his fellow researchers have devised a new fiery experiment for astronauts. The experiment, which was scheduled to launch to the ISS on a resupply mission today, will study how fire spreads in small, confined spaces. A blaze inside a building or a spaceship behaves differently than it does in open spaces, and the researchers hope this work could inspire better infrastructure design and fire-safety codes.

Studying fire in space is actually easier than doing it on Earth. Fire is complicated here. A single candle flame contains thousands of chemical reactions. The heat of the flame vaporizes wax and breaks down its molecules into carbon and hydrogen, which combine with oxygen in the air to produce light, heat, carbon dioxide, and water vapor. As hot air rises to the top, fresh, cooler air is drawn in at the bottom, providing fuel for the flame. This flow molds the flame into a teardrop and makes it flicker.

On Earth, the flickering hides the subtle dynamics of fire. In space, this flow doesn’t exist. Air travels in all directions, and the flame rounds out. Without interference from gravity, scientists can get a better look. “Flame balls are to combustion scientists what fruit flies are to geneticists,” Paul Ronney, a combustion researcher, once said. “It’s not that we want more fruit flies, or flame balls, but they provide a simple model for testing hypotheses and checking computer models.” (MORE - details)

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