Languorous Liquids

The physics is hard enough, but the scientists had to tackle another problem as well: Because room for sending research equipment up to the station is limited while the shuttle fleet is grounded, the researchers had to find a way to do their experiment using things that can be tucked inside a Russian Progress supply rocket or found already onboard the station.

"I have selected 8 liquids for testing," says Ethridge. "They've been loaded in syringes that will be launched on a Progress rocket to the space station." One of them is ordinary honey. Although it only crystallizes very slowly, honey is actually an undercooled liquid. It works just fine for proving that this "floating drop" method can accurately measure a liquid's viscosity.

The strength and elasticity of amorphous solids ("glassy alloys") exceed that of many other materials.

The experiment goes like this: Honey (or one of the other liquids) will be squeezed from its syringe and transferred onto thin strings. "Nomex thread and string is available on the space station and can be used to confine and control the liquid drops in orbit. Thin solder wire may also be used to manipulate the drops," notes Ethridge. With a drop clinging to each of two strings, a crew member will bring them slowly together, allowing the drops to gently touch and merge. A video camera kept aboard the station will record what happens as the drops slowly form a peanut shape and eventually a single sphere.

Back on the ground, researchers will examine the footage frame by frame to determine exactly how fast the drops merged. Because the viscosity of the test samples is already known, researchers can compare the measured value with the real value to see if they're on the right track.

The researchers currently plan to conduct the FMVM experiment sometime during Expedition 8, which is scheduled to begin in late October 2003. Their work could result in a new way of knowing the viscosity of undercooled liquids. And after that... no one knows, but golf clubs and kitchenware are probably just the beginning.