What happens when you boil water in space?


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Keith Rohan
November 13, 2019 4:26PM

In microgravity environments, boiling works very differently than it does on Earth. Under our gravity conditions, hotter parts of the liquid rise, while cooler parts sink. When vapor bubbles begin to form, they get shot upward, creating that classic "rolling boil."

In space, though, heated liquid doesn't rise, so it just sits next to the heater and gets hotter. Likewise, as bubbles of vapor form, they don't rise to the surface. Instead, they form one big bubble that moves through the liquid. Sometimes, that big bubble sticks to the heat source, preventing the rest of the liquid from boiling.

Other times, the liquid doesn't boil at all. Astronauts aboard the International Space Station have gotten liquids up to 160 degrees Kelvin above their normal boiling temperatures, and since "superheating" a liquid like that can be dangerous, they couldn't heat it any more than that for safety reasons.

All that's to say that microgravity makes hot liquids behave weirdly, and scientists don't have it all figured out.