When you make a salad dressing, you shake together oil and acid to suspend tiny droplets of the latter in the former. Leave it on the counter for a few hours, though, and gravity separates it out into layers of its component liquids. So how would you perform that separation in space?

It sounds like a silly question, but in fact separating liquid in space is a big deal: to re-use clean water, primarily, but it could be applied to cooling fluids, fuel and others, too. Sadly, without gravity the molecules of liquid have no weight, so if they’re put into suspensions—like the salad dressing—they’ll just stay there.


Researchers at the Microgravity Research Center at Free University of Brussels, Belgium, though, have been working out how perform separation without gravity—and that’s what you ca see in this image. A mixture of water and alcohol would usually separate on Earth, with the lighter alcohol settling on top of the water. But in zero-gravity the researchers found that slowly vibrating the liquid forces it separate out into distinct columns, as you ca see in the image. From there—in theory, at least—it’s possible to draw out most of the required liquid while leaving the rest behind. [ESA]

Image by Microgravity Research Center, ULB, Brussels–V. Shevtsova

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