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| Last August, ENG graduate student Charlie Thomas ('01) did what chronic dieters long to do: he lost a lot of weight in a hurry. In fact, he lost his entire body weight- and then gained it all back, and doubled it, in about a minute. All that was just par for the course on board NASA's KC-135A research plane, an aircraft originally used to prepare astronauts to withstand the effects of zero-gravity conditions in space. Thomas and his advisor, Assistant Professor of Aerospace and Mechanical Engineering Glynn Holt, flew four two-hour missions on the plane, conducting an experiment that investigated the effects of gravity-and zero gravity-on the phenomenon of sonoluminescence. Able ground-crew assistance came from Sean Wyatt ('00), who earned a master's for his work on the subject and had written most of the computer code that ran the experiment. Wyatt worked with Thomas and Holt from the plane's base at the Johnson Space Center in Houston. The KC-135A defies gravity by cutting a roller coaster-like path through the sky over the Gulf of Mexico, tracing a series of parabolas that create periods of weightlessness for passengers and objects inside. The craft climbs at about a 50-degree angle to about 34,000 feet, and then it plunges toward the sea in a 45-degree free-fall to about 24,000 feet. No wonder it's known as the Vomit Comet. As the plane performs its maneuvers, forty parabolas per two-hour flight, nausea can be a constant companion. "You don't know what's up and what's down," Thomas says. "You know logically which way is up, but you don't feel it." Weightlessness happens at the top arc of each parabola; for twenty-five magical seconds, people float upwards, turn somersaults in the air, and watch, grinning, as pens and paper and everything else hang suspended in air. Then, near the bottom of each arc, gravity is restored, slamming everything that had been floating to the floor. As the plane turns its nose upward, the force of gravity nearly doubles: limbs feel heavy, blood seems to run slower, heavier, through the veins, and a sensation similar to sleepiness briefly takes hold, according to many passengers. And then it ends, and the cycle starts over again, and again, and again. Thomas freely admits that his experiences aboard the plane, particularly on the first day, lent authenticity to the craft's nickname. During that first mission, after about ten parabolas, he had to leave his experiment to go sit down; he was sick more than a few times, but he was reassured by the flight crew that his response was common, even among experienced astronauts. On his next flight, he made sure to avail himself of NASA's motion sickness drugs-"half antihistamine, half downer," Thomas says-and he gradually got used to the gravity shifts. The group's experiment was productive. Sonolum-inescence-literally, making light from sound-is a hot topic among engineers and physicists, with possible energy-harnessing applications and a potential role in thermonuclear fusion reactions. The phenomenon, still largely unexplained, happens when single bubbles of gas in a liquid are trapped in a sufficiently intense sound field; they then emit short pulses of light bright enough to be seen in an undarkened room. Thomas, Wyatt, and Holt were looking at what happens during shifts in gravity to the intensity of the bubble's light and to the position of the bubble in its liquid cell. They saw that the bubbles move up and down, and expand and contract, depending on gravity. They also saw that at double gravity, the bubble glowed less brightly than at zero gravity. Thomas's fascination with bubble theory, as he refers to it, grew out of a fascination with sound in general. After studying physics and playing the French horn as an undergraduate at the University of Rochester, Thomas came to ENG for his master's degree, wanting to design concert halls. He continues to play the French horn, but his interest in acoustics has taken him in a different direction. "Now I'm thinking I'd love to study bubbles," he says with a smile. And he'd love to have another go at the KC-135A, now that he's conquered zero gravity. | |||||
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