The Physicsof Orange Juice
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The Physics of Orange Juice Shuttle experiments target the behavior of fluid
mixtures in microgravity
November 3, 1998: Imagine trying to pour a glass of
orange juice in zero gravity. It may not be as easy as it sounds.
Without gravity to pull the fluid into the cup, you might end
up with a room full of orange mist -- tiny drops of OJ held together
by surface tension. How to control drops of fluid in low gravity,
and what happens inside a "colloidal mixture" like
orange juice (pulp suspended in a thinner fluid), are the subjects
of three fluid physics experiments on shuttle Discovery.
The Physics of Orange Juice
Colloidal mixtures are systems of fine particles suspended in
fluid. Milk, orange juice, and paint are some common examples.
On Earth, gravity causes the denser particles in a colloidal
suspension to settle to the bottom, which is why some colloids,
like orange juice and paint, must be stirred before use. Microgravity
enables scientists to study colloids because the effects of density
differences between particles and their surrounding fluids are
decreased. "Settling" is less of a problem, and it's
possible to maintain an even distribution of particles in the
fluid. That's a big improvement over fluid experiments conducted
To many people, gloveboxes are what medical researchers use to separate themselves from deadly viruses. But gloveboxes come in many shapes and sizes. The Microgravity Science Glovebox, developed at the NASA Marshall Space Flight Center, is designed for hands-on work inside the shuttle in the microgravity environment of space.
"It's a useful device, to have a work station where you can run many different kinds of experiments, where the crew can do hands-on work, where you can make changes on the fly," said project scientist Don Reiss of NASA Marshall's Space Sciences Laboratory. This week the crew of Shuttle Discovery will use the glovebox for experiments with fluids in space. more information
|Experiment test samples will contain plastic spheres that are about one-tenth of the thickness of a human hair in diameter. In orbit, the samples will sit for several days while the spheres organize themselves. The spheres, like atoms, will settle into an arrangement that gives each sphere the most space. A sample with a low concentration of spheres is expected to maintain fluid movement, like atoms in a liquid. In samples with a very high concentration of spheres, no crystals will form. This last behavior is similar to the solidification of liquids into glass materials in which the atoms move so slowly that it takes millions of years for them to organize into crystalline structures.|
|For CDOT and another ongoing experiment, Structural Studies of Colloidal Suspensions (CGEL), researchers will shine laser light through the colloidal samples to study the arrangements of suspended particles. The laser light will be scattered from the surface of the structures, similar to the way sunlight "sparkles" on snow flakes.|
While these investigations are being conducted inside the glovebox,
three video cameras will record the action. These data are transmitted
to scientists on Earth, allowing them to instruct the crew to
make experimental adjustments if necessary. |
Right: Shuttle video from STS-94. Deformation of a drop of water using ultrasound.
Â NASA Space Shuttle home page
Blasts off with John Glenn -- 29 October 98 NASA Space Science
One small switch for a man... John Glenn activates a landmark materials science experiment while aboard STS-95. 30 October 98 NASA Science News
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