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USU HOPES FOR GOOD VIBRATIONS

A 2-foot-long aluminum truss will be shipped from Logan to Florida next week so it can fly on a space shuttle this summer.

The experiment is the climax of a five-year, $770,000 Utah State University study to help predict how antenna booms and other structures vibrate on spacecraft.It already was tested in low gravity aboard the National Aeronautics and Space Administration's "vomit comet," a KC-135 aircraft that flew out of Johnson Space Center, Texas, last year. People and experiments on the plane experience near-weightlessness during the downhill parts of the plane's roller-coaster-like flights.

"Trust me, it was gruesome," said Steve Folkman, who heads the USU project and rode the plane.

"We all thought you throw up and that's it. But it makes you violently ill," said Folkman, an assistant professor of mechanical and aerospace engineering.

It will be the sixth time Utah State has had an experiment aboard a shuttle.

It is scheduled to be flown July 20-31 but could be delayed because of a possible delay in a scheduled June flight that will see another shuttle dock with the Russian Mir space station.

The USU-built truss is similar to larger trusses that serve as booms supporting antennas or other equipment on many spacecraft, but instead of having tight joints its struts are connected by inch-long pins.

That kind of joint, called a clevis-tang joint, is easier to build than a tight joint, but the holes leave room for the pins to wiggle, and it is hard to predict how the wiggling motion affects the vibration of the entire truss.

Aboard the shuttle, a set of motors and magnets will pull the truss in various directions, then release it so it "twangs" slightly back and forth. A computer will record the rate of vibration and how long it takes to stop.

So far, said Folkman, the experiment on the airplane showed vibrations end more quickly in low gravity than on Earth.