Material Science Investigations

Miscible Fluids in Microgravity (MFMG)
A zero-upmass experiment scheduled for Increment 8

John A. Pojman, Principal Investigator Professor, Dept of Chemistry and Biochemistry University of Southern Mississippi john@pojman.com www.pojman.com

Quicktime Movies Honey Into Water Water Into Honey Centrifuge

Description of the Experiment
The Miscible Fluid in Microgravity (MFMG) experiment will test how miscible fluids, that is, fluids that completely dissolve in each other, interact without the interference of gravity. Immiscible fluids, like oil and water, exhibit what is called an interfacial tension because of the different ways that each type of molecules pull on each other. This interfacial (surface) tension allows a water skeeter to walk on water.

If a stream of one immiscible fluid is injected into another in weightlessness, the stream will break into drops with a diameter equal to p times the diameter of the injector. This is called the Rayleigh-Tomotika instability. We will test if the same breakup occurs with two miscible fluids by injecting honey into water and observe if the honey stream breaks into drops, and if so, measure the size of the drops.

Because the honey is more dense than water, the stream sinks in the water when we try to do the experiment on earth.

A drop of an immiscible fluid in another fluid will always become spherical in weightlessness. We will test if an irregular drop of water injected into honey does the same. To prevent the drop from floating to the top of the honey, the experiment must be performed in weightlessness.

Both experiments will also be performed while heating the fluids to test if miscible fluids migrate - something that is seen with immiscible drops and streams.

Importance of the Experiment
One hundred years ago, a scientist named Korteweg predicted that miscible fluids could act like immiscible fluids until they had diffused and become uniform. Although there has been much theory and some provocative experiments during the intervening century, no definitive experiments have been performed. This simple experiment will be a step toward a complete test of Korteweg's hypothesis.

Relevance of the Experiment
Although the phenomena in the MFMG experiment can only be observed in weightlessness, there are 'down to earth' implications of the results. The models used to simulate the experiment provide information on the fundamental interactions between molecules, and the results of the experiment could help us develop improved understanding of processes ranging from the dissolving of plastics to protein crystal growth.

Related Links

• Dr. John Pojman
• ISS Science Operations News
• NASA News Release
• Fact Sheet