Wednesday, February 28, 2007


What do you get when you add ordinary air or even an Alka-Seltzer to a spherical water drop in microgravity? Expedition Six NASA ISS Science Officer Don Pettit performs a series of microgravity experiments with water spheres and effervescent antacid tablets. You can find them all on youtube,tagged under microgravity.

Here we have a liquid film made of very little water stretched across a wire loop. We simply drop an effervescent tablet into the middle. You can see that the volume expansion is quite significant as chemicals in the tablet (baking soda and citric acid) dissolve in water and then react to form carbon dioxide gas. The resultant bubbles inflate the film.

The next time you're watching a pot of water boil, perhaps for coffee or a cup of soup, pause for a moment and consider: what would this look like in space? Would the turbulent bubbles rise or fall? And how big would they be? Would the liquid stay in the pan at all? Until a few years ago, nobody knew. Indeed, physicists have trouble understanding the complex behavior of boiling fluids here on Earth. Perhaps boiling in space would prove even more baffling.... It's an important question because boiling happens not only in coffee pots, but also in power plants and spacecraft cooling systems.

[+ fizzing]
[+ boiling]
via science.nasa.gov

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