Remote Control of Experiments Helps Shuttle in Materials Science

WHILE space shuttle Columbia orbits Earth, ground-based scientists, so to speak, work side by side with the astronauts. These scientists, however, are on board only in electronic form.

It's called ``telescience'' - working experiments by radio control. For Earth-based scientists managing the United States Microgravity Payload (USMP) mounted in Columbia's cargo bay, this is the next best thing to being there. It actually enables them to control and fine-tune delicate experiments.

Telescientists at the Spacelab Mission Operations Control Center in Huntsville, Ala., are taking advantage of Columbia's weightless state to study abstruse aspects of materials science that has down-to-earth practicality. Without such gravity-induced complications as convection in molten materials, they are getting a clearer view of the phenomena they are investigating.

Take, for example, what physicists call a fluid's ``critical point.'' That's when the combination of temperature and pressure allow a fluid to exist simultaneously as a gas and a liquid with the same density.

That sounds like something only a physicist would love. But these days, it's as relevant to everyday living as a cup of decaffeinated coffee. Fluids at their critical point are finding practical uses. By using water in this ambiguous state, for example, processors remove caffeine from coffee. They no longer need methylene chloride - a chemical that produced a hazardous waste.

Scientists on the Zeno experiment are making measurements much closer to the critical-point temperature than they can on Earth. Project scientist Jeff Shaumeyer reported coming within 20 millionths of a centigrade degree of the critical point for xenon by Columbia's second day on orbit. That means taking measurements 25 times closer to the exact critical-point temperature than scientists can do on Earth. Also, because there is no gravity to produce density variations, the team has a larger percentage of its sample in the critical-point state than it would have on the ground.

Other experiments in the USMP are directly related to the quality of computer chips or the strength of the steel in an automobile or the aluminum in an airplane.