ATHENS, Ohio (June 8, 2005) -- Remember your last airplane ride? Watching the plane's shadow skim the tops of the clouds, while you sipped cola from one of those little plastic cups? Now imagine what your reaction would have been if the plane suddenly nose-dived at almost 400 mph, fast enough to cause every pretzel in your tiny bag to float weightlessly before your eyes. That is, until the crazy pilot reared the plane back up again, bringing those airborne snacks crashing to the floor at twice their normal weight.
This spring, Dennis Irwin, dean of the Fritz J. and Dolores H. Russ College of Engineering and Technology at Ohio University, and two engineering professors participated in the European Space Agency's 39th Parabolic Flight Campaign to research how astronauts use bodily and visual cues to interpret their body orientation.
As part of the campaign, they experienced such nose-dives and weightlessness for themselves during parabolic flights, when the path of the plane follows not a straight line, but a parabola, with steep, upward climbs that simulate twice-normal earth gravity, followed by sharp dives that simulate near-zero gravity.
Irwin and visiting professor Angie Bukley, under the direction of Gilles Clement from the French National Center of Scientific Research (CNRS) in Toulouse, France, used the 12-to-15 minutes total of zero gravity to determine how blindfolded test subjects perceive their body orientation when weightless. All three, as well as eight other flight participants, served as test subjects.
"We masked our eyes so there was no visual input. And in zero gravity, there is no reliable information coming from the inner ear," Irwin said.
In normal gravity, humans can determine the angle of their torsos relative to their heads within half a degree using just the sensory information from their inner ears, muscles and skin. However, research shows that in zero gravity, that error increases dramatically.
"We found that this error could go up to 15 degrees in some individuals in microgravity during parabolic flight," said Clement, "suggesting that gravitational information is very important for knowing where our body parts are relative to each other."
The information has wide implications for research concerning human sensory and balance systems. It is research intended to treat sensory-challenged individuals and help develop perception aids for pilots and astronauts.
Astronauts often suffer from motion sickness that can last the duration of their flights. That often-severe nausea is generally thought to be caused by the fact that, without gravity, astronauts sometimes feel that their bodies are positioned one way when they actually are not. The zero-gravity research will be used to find ways to prevent such motion sickness.
Other than losing one member of their research team to the motion sickness, the experiment went according to plan. Subjects wore masks with small LED screens showing two lines the subjects could turn to represent their perceived vertical orientation of their bodies during the plane's different movements. Considering the frame of such complicated machinery began life as a Rubbermaid salad bowl when in development, its precise functioning might sound surprising.
But Bukley said such experimental resourcefulness is not unheard of. "It's not the first time I've seen salad bowls converted into flight equipment," she said.
Bukley also said that weightlessness posed its own challenges to the researchers, but that they nonetheless captured the information they needed.
"The hard part was conducting the experiment, not being a test subject," Bukley said. "When you're in zero-G, trying to get in position to read meters on a subject who's in free-fall is not simple."
Both Clement and Bukley have been on countless parabolic flights, but this was Irwin's first. He described losing and then regaining gravity as peculiar.
"It feels as if all of a sudden, there is a flushing out of your entire body - as if all of your cells are being released. It's just a very distinct lack of any pressure anywhere on your body. Then when the hypergravity took over, I felt as if different parts of my body were falling at a different rate than others."
The combined aerospace-related experience of the trio brought varying expertise to the experiment. Irwin worked on NASA-funded grants from 1989-1997 in the area of vibration suppression and pointing control for large, flexible space structures.
This fall, Clement will begin teaching biomedical engineering at the Russ College, holding technical seminars about space-life sciences and how to perform life sciences experiments onboard spacecraft. Currently, he is a director of research at CNRS and teaches in all areas of space life sciences at the Faculty of Medicine in Toulouse, France, as well as at the International Space University in Strasbourg, France.
Bukley, who began teaching electrical engineering and computer science at the Russ College in 2004 as the college's Stocker Visiting Professor, previously was aerospace engineer at Aerospace, Corp. The company is the U.S. Air Force's primary research and development group. Bukley is also on the faculty of the International Space University where she teaches space engineering courses.
[ 30 ]