April 15, 2003click on either of these images to view the complete 4 Mb Quicktime movie

Blowing Bubbles
Credit: Don Pettit, ISS Expedition 6 Science Officer, NASA

Explanation: Not long ago International Space Station science officer Don Pettit discovered the amazing properties of watery thin films in space: They're remarkably tough. You can shake them, spin them, even paint on them.

Now he's learned how to blow them up, too.

It's done using Alka Seltzer^TM. Don describes the procedure: "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 fate of bubbles in a liquid is an important topic for operations in low gravity. Whether you're designing a science experiment or a piece of engineering equipment that is supposed to work in this environment, it's really important to understand what happens to gas in liquid and vice versa. I'm hoping this demonstration will give [designers] some ideas about what might happen to their systems up here and maybe inspire some new experiments."

The full-length video of his demonstration shows how tiny bubbles swirl (hypnotically) in a stirred film, how small bubbles combine to form bigger and bigger pockets of gas, and how unwanted bubbles can be removed from gas-contaminated fluids using a syringe.

"These thin films really are a wonderful tool for experimentation." So what's next? "The best is still ahead," he says. Stay tuned....

Editor's note: Don Pettit has done similar experiments involving effervescent tablets and spheres of water (rather than films of water). See the entire series: Reel 1 (2Mb); Reel 2 (4Mb); Reel 3 (2Mb); Reel 4 (4Mb)