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Gravitational Relativistic Physics (GRP)
Low Temperature and Condensed Matter Physics
    PRESENT: Ongoing Reseach

Launch Date: Flew August 1997 -Will fly again on a future Space Shuttle flight
Mission Duration: Several days
Principle Investigator: Dr. Robert Berg, NIST Gaithersburg


Key Questions We Want to Answer:

Molasses flows slower than water because is has a greater viscosity-a property resulting from the interactions between a fluid's molecules. These interactions are so complicated that the viscosity of few fluids can be accurately calculated from theory. Experiments must be conducted to measure viscosity.

What We Already Know:

Although the critical temperature and viscosity can differ greatly among fluids, there is a remarkable regularity in the relative size of viscosity increase for all pure fluids. Current theories predict this increase in viscosity at the critical point to be universal behavior, and relate the increase in viscosity to spontaneous fluctuations in density near the critical point of the phase transition between liquid and gas states.

The Critical Viscosity of Xenon (CVX) experiment will test these theories with great precision. Xenon was chosen because it is a simple fluid, its other critical properties have been thoroughly explored and its critical temperature is near room temperature. Having this information would also aid the analysis of the data from the previously-flown ZENO mission, which is designed to better understand the light scattering aspect of the same phase transition.

What We Hope to Find Out:

To measure the viscosity, liquid xenon is placed in a container with a small paddle that vibrates. By measuring the drag force on the moving paddle, the viscosity of the material can be measured. Measuring the viscosity in this manner as the sample of xenon is caused to approach the phase transition allows the experimenter to study the properties of the material near the critical phase transition. The experiment is about 1 inch by 2 inches in size.

How We'll Conduct Our Experiment:

To achieve the most accurate results, it is best to measure the viscosity of xenon closer to the transition from fluid to superfluid state, in a microgravity environment. The absence of gravity allows for creation of a more uniform sample than is possible on the ground. The larger, more uniform sample improves accuracy of the measurement results by at least 100 times.

Additional information:

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