Why do fluids boil in space

Using a freon coolant as their liquid, they conducted a series of boiling experiments on the space shuttle during 5 missions between to And indeed, they found some intriguing differences between what happens to boiling fluids on Earth and what happens to them in orbit. For example, a liquid boiling in weightlessness produces -- not thousands of effervescing bubbles -- but one giant undulating bubble that swallows up smaller ones!

The research could also have applications here on Earth. The weightless environment gives scientists a new "window" into the phenomenon of boiling. Scientists can use this perspective to improve their understanding of the fundamentals of boiling, which might be used to improve the design of terrestrial power plants.

In the free-fall of orbit, boiling is simpler than it is on Earth. Weightlessness effectively removes two of the variables in boiling -- convection and buoyancy. This difference explains why boiling liquids behave so differently in space. It also provides a powerful tool for scientists who want to unravel the tangled physics of boiling.

You would also want to look at a simpler planet with fewer variables. One thing space does for us is simplify the problem that we're studying," Chiaramonte says. When a pool of liquid is heated on Earth, gravity causes hotter regions in the liquid to rise, and cooler, more dense parts to sink -- a process called "convection. It boils, and it boils quite violently at that! The reason for this is that water, in its liquid phase, requires both a certain range of pressure and a certain range of temperatures.

If you start with liquid water at a given fixed temperature, a low enough pressure will cause the water to immediately boil. In the liquid phase, dropping the pressure significantly can result in a solid ice or a gas water Image credit: wikimedia commons user Matthieumarechal. But on that first hand, again, if you start with liquid water at a given, fixed pressure, and you lower the temperature, that will cause the water to immediately freeze! You can bring liquid water to space aboard, say, the international space station where it can be kept in Earth-like conditions: at a stable temperature and pressure.

Does it freeze or boil? The surprising answer is it does both: first it boils and then it freezes! We know this because this is what used to happen when astronauts felt the call of nature while in space. When the astronauts take a leak while on a mission and expel the result into space, it boils violently. The vapor then passes immediately into the solid state a process known as desublimation , and you end up with a cloud of very fine crystals of frozen urine.

The specific heats of various materials, elements and compounds. Note that liquid water has one of Furthermore, because of surface tension, water tends to remain in spherical shapes in space as you saw above , which actually minimize the amount of surface area it has to exchange heat with its subzero environment.

Which happens first? What is the boiling point of water in a vacuum, anyway? As it turns out, the answer to this question is known. When astronauts urinate in space and release the contents, the urine rapidly boils into vapor, which immediately desublimates or crystallizes directly from the gas to solid phase into tiny urine crystals.

Urine isn't completely water, but you'd expect the same process to occur with a glass of water as with astronaut waste. Space isn't actually cold because the temperature is a measure of the movement of molecules.

If you don't have matter, as in a vacuum, you don't have temperature. The heat imparted to the glass of water would depend on whether it was in sunlight, in contact with another surface or out on its own in the dark.

That's quite a temperature difference! However, it doesn't matter much when the pressure is nearly a vacuum. Think about water on Earth. Water boils more readily on a mountaintop than at sea level. In fact, you could drink a cup of boiling water on some mountains and not get burned! In the lab, you can make water boil at room temperature simply by applying a partial vacuum to it.

That's what you would expect to happen in space. While it's impractical to visit space to see the water boil, you can see the effect without leaving the comfort of your home or classroom.

So the boiling point could easily drop to your body temperature. That means your saliva would boil off your tongue and the liquids in your blood would start to boil. All that bubbly boiling blood could block blood flow to vital organs. That in itself could kill you.

And if the bubbles pass through your heart, it could cause a heart attack. The bubbling would also probably burst some capillaries , so you could find yourself covered in splotchy bruises. If the liquid in your blood stream started boiling, it would turn into gas that would make your skin swell.

NASA makes it clear that your body wouldn't explode and your eyes wouldn't pop out of your head like many science fiction movies suggest.

However, you would swell up and get really painfully puffy. Even while you're floating there unconscious and puffy, your troubles aren't over. If you end up facing the sun when you get sucked out of your spaceship, then you'll probably be drifting through temperatures around degrees Fahrenheit.

That means an instant sunburn. You'd also be bombarded with radiation from other stars besides the sun. Harmful UV light, gamma rays, and x-rays can warp your cells.