Candles in microgravity

What happens to a candle burning in microgravity, say aboard the International Space Station (ISS)? On the Earth, the flame 'points' upwards because the hotter, less dense combustion products in the flame rise. Fresh oxygen is then drawn in at the bottom of the flame keeping the process going. In microgravity, things are a bit different. There is no buoyant convection so the products of the burning candle remain around the candle, slowly moving away in all directions. This also means that there is less draw on the oxygen which only gets to the flame by molecular diffusion. This is a slower process so it is quite possible for the flame to die out.

Are the flames really spherical and self-extinguishing? Back in 1996, investigators from NASA Lewis performed 79 candle burns in an experiment aboard the MIR space station. What they found was that the candles didn't quite go out, as had been expected, but showed "spontaneous and prolonged flame oscillations" near extinction. Flames in microgravity are pretty strange.

Posted in astro blog by Stuart on Saturday 22nd Jan 2005 (17:49 UTC) | Permalink
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