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Space Station Ingenuity



Submitted by Arthur - N1ORC

Submitted by Arthur - N1ORC


For pictures see NASA Science Site



Sept. 25, 2003:  Here's a challenge for you: Using only what you can
find lying around your house, put together an experiment to test a
question in science that's never been answered.

That's essentially the challenge faced by some scientists who want their
research done onboard the International Space Station (ISS). With the
shuttle fleet grounded and space limited on Russian rockets, it's not
easy to send their equipment to orbit. What can they do?

Improvise.

Astronauts onboard the station are adaptable, natural experimenters, and
they don't always need fancy equipment to do science. So researchers
have dreamed up some clever ways to use what's already on hand aboard
the station: maintenance tools, food supplies, hygiene items, cameras
... and, of course, weightlessness.

Above: Cosmonaut Nikolai M. Budarin, Expedition Six flight engineer,
squeezes inside a Soyuz spacecraft. Space is tight. [more]




The surprisingly elegant experiments they've devised are a showcase of
resourcefulness. Over the next few weeks, Science@NASA will feature a
series of articles about these experiments, showing how ordinary items
can be used for science in space.

We begin with Miscible Fluids in Microgravity, an experiment concocted
by University of Southern Mississippi chemistry professor John Pojman
with colleagues Vitaly Volpert and Nick Bessonov of the Université Lyon
I in France. They want to find out what happens when two miscible fluids
are combined in microgravity.

"Miscible means mixable," explains Pojman. "When miscible fluids are
combined, they merge. For instance, water and molasses are miscible. One
diffuses completely into the other. Immiscible fluids are just the
opposite; they remain separated like oil and water."

Sounds simple. But 100 years ago a Dutch physicist named Diederik
Korteweg pointed out a complication: sometimes miscible fluids act like
immiscible fluids.

Indeed, you can see this in your own kitchen using water and molasses.
Fill a clear cup with water. Next, dip a spoon into a jar of molasses,
and tip the spoon over the cup. A stream of pure syrup will plunge to
the bottom. At first the goopy molasses seems to ignore the surrounding
water. For a little while they seem to be immiscible. Eventually,
though, the syrup dissolves.

Left: A 19th century photograph of Diederik Korteweg. [more]

Korteweg was fascinated by what happens during that curious time just
after miscible fluids are combined and just before they dissolve. Do
they really behave like immiscible fluids? Korteweg knew that immiscible
fluids tend to break apart into little droplets--a side-effect of
surface tension. He calculated that miscible fluids should break apart
in the same way during the early moments of gentle mixing.

Miscible fluids, gently mixed, are widely used in the plastics industry
and they're necessary for certain types of medical research--"especially
protein crystal growth in microgravity," notes Pojman. How they merge,
dissolving evenly or breaking apart into droplets, actually makes a
difference.

Yet no one knows if Korteweg was right. "It's impossible to test his
theory on Earth because gravity overwhelms surface tension," says
Pojman. Fluid streams fall apart because of their own weight. "We need
to do this experiment in space."

Right: Pojman has tried the experiment before using water and glycerine
onboard NASA's KC-135 "Vomit Comet." Only a few seconds of good
microgravity could be achieved--not enough to solve the puzzle. Image
courtesy John Pojman.

Pojman has planned for some time to investigate the problem using a
sophisticated experiment called Transient Interfacial Phenomena in
Miscible Polymer Systems, but the equipment won't arrive on station
until later this decade. Meanwhile, he's going to get a preview of the
physics from Miscible Fluids in Microgravity.

The first thing they need for their experiment is some kind of container
in which to do it. The container needn't be large, but it must be
transparent so that cameras can record the outcome.

Unused urine collection syringes fit the bill perfectly. Cameras that
the space station crew uses to document life in orbit fill the
data-acquisition role. A video camera will film the entire 10-minute
experiment, and a digital still camera will snap shots every 30 seconds.

While the body of one syringe serves as a container for the first fluid,
the needle of another syringe will slowly inject a stream of the second
fluid.

Air bubbles could spoil the experiment, Pojman says. To plug small holes
in the syringes that could introduce air bubbles, Pojman considered a
widely used sealant: chewing gum. "I like the idea of an experiment that
uses chewing gum," Pojman jokes. Nevertheless, they ultimately chose to
use Duxseal™, a plumber's leak-repair compound from the station's
maintenance kit.

Left: Professor Pojman displays the prototype MFMG experiment. Bob
Powell, a NASA expert on developing procedures for microgravity
experiments, looks over his shoulder. Image courtesy NASA.

Water was an obvious choice for the first fluid, but what about the
second one? Pojman says they considered several of the materials
available on the station: shampoo, shaving cream, even ultrasound gel.
(The space station is equipped with an ultrasound imager for use in
medical experiments.)

In the end they settled on honey. The crew has cans of Russian honey on
board to use for sweetening their tea. As anyone who has had honey in
their tea before knows, honey dissolves in water quite nicely--i.e.,
water and honey are miscible.

One small Ziplock™ bag will serve as a reservoir for the water, and two
larger bags will dispose of the leftover waste.

Voilà! A microgravity experiment, no custom-built equipment required.

Miscible Fluids in Microgravity will probably take place before the end
of this year. Although it won't answer all the questions about
Korteweg's ideas, it's an important prelude to experiments that will.
Not bad for a few odds and ends … and a little ingenuity.



Vitaly Volpert and Nick Bessonov of France have performed computer
simulations that show a stream of a miscible fluids can break apart from
the Korteweg stress and an elliptical drop will become spherical – just
as seen with immiscible fluids. "The great unknown,” says John Pojman,
"are the values of the parameter describing the intermolecular
interactions.” Performing the Miscible Fluids in Microgravity experiment
will help his team estimate this value and to test their model.

Miscible Fluids in Microgravity (MFMG) is a prelude to a more
sophisticated space-experiment called Transient Interfacial Phenomena in
Miscible Polymer Systems (TIPMPS) led by John Pojman, Vitaly Volpert and
Hermann Wilke of Berlin, Germany. TIPMIPS is planned for later this
decade. Meanwhile, Pojman is interested in gathering information to test
their computer models--hence MFMG.

Diederik Korteweg -- biographical information about the Dutch scientist
who first proposed the theory mentioned in this article

Videos: click here for a 5.3 MB QuickTime movie of Professor Pojman
doing an earlier miscible fluids experiment aboard the KC-135 "Vomit
Comet"; click here for a 1.8 MB movie close-up of the samples during
that experiment. Videos courtesy John Pojman.

Press release -- about this research, from the University of Southern
Mississippi
 







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