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May 19, 2002

The greatest footage since the LOX barbecue and the exploding whale
Posted by Teresa at 04:17 AM *

This is so cool that I can’t believe it’s a NASA site. The page’s headline gets straight to the point: Did you ever wonder what it would be like to pop a water balloon in space?

Well, of course.

They’ve got footage of utterly captivating water-balloon-popping experiments in the Vomit Comet. Dye and soda straws come into it too. They even make it sound legitimately scientific:

The tests were conducted in part to develop the ability to rapidly deploy large liquid drops by rupturing an enclosing membrane. As can be seen from the experiment footage, the initial rupture process is nearly ideal, but the finite size of the balloon material eventually ejects a spray from the drop surface. Then, when the balloon material leaves the drop entirely, it causes a large deformation of the drop (blob) which oscillates throughout the remainder of the test. Calculations suggest that such oscillations will continue for hours before the drop eventually becomes spherical.
Uh-huh, yeah. Do the one again with the raspberry-colored blob. (Thanks once more to Erik Olson.)
Comments on The greatest footage since the LOX barbecue and the exploding whale:
#1 ::: Bob Webber ::: (view all by) ::: May 19, 2002, 05:55 PM:

I wonder what that would be like with a rheopectic non-Newtonian plastic material like corn starch suspension. Places where the surface's rate of flexing is increasing faster, i.e. right around the base of any traveling bulges, would be stiffer.

Since the reaction force for the rebounding of the balloon's skin is all going to come from the final point of contact of the balloon skin and the blob, the shear forces that make the bulge in the first place are going to be concentrated in a small area, so the surface of the cornstarch blob on the side that got the kick would tend to stiffen into a cup, and less of the energy of the balloon skin's contraction would be randomized in changes in the blob's surface energy as it changed shape.

So I think that something rheopectic, like cornstarch suspensions, would probably achieve a higher linear velocity than something closer to an ideal fluid, like water. The only application I have thought of for this is a novel way to eat Jell-O™ low-fat pudding in a microgravity environment.

#2 ::: Teresa Nielsen Hayden ::: (view all by) ::: May 22, 2002, 12:35 AM:

Hmmm. If there were enough turbulence when the balloon popped, you might get cracking, or even have chunks exiting the blob. Below a certain point, though, my guess is that mild shimmying would help stick the blob back together.

This reminds me of those physics problems where you try to figure out what would happen if our entire planet were instantaneously turned from rock into water.

#3 ::: Teresa Nielsen Hayden ::: (view all by) ::: May 22, 2002, 01:00 PM:

The other thing it reminds me of is that great scene of Mike Ford's -- was it in =Princes of the Air=? -- where they're doing tempura in Zero-G.

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