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Living in zero gravity

Astrophysicist and astronaut Tamara Jernigan loves how it feels to float. Her greatest disappointment on returning to Earth from last June's space shuttle flight was no longer being able to move just by pushing off an object.

Speaking to a centennial class in Stanford's Physics Tank on Sept. 29, Jernigan showed just how far a Stanford graduate can go -- in her case, 160 nautical miles above Earth.

Jernigan joined the astronaut program while a student at Stanford, where she received a bachelor's degree in physics in 1981 and a master's in aeronautics and astronautics in 1983. She later earned a doctorate in space physics from Rice University.

Last June Jernigan became the 15th U.S. woman in space as a crew member on Space Lab Life Sciences One, a nine-day biomedical research flight testing how the human body adapts to zero gravity and readapts to earth's gravity. One concern was understanding the causes of space adaptation sickness -- what Jernigan said astronauts call the "space barfs" -- the nausea that can accompany space flight, particularly during the first 24 hours.

A variety of experiments tested the cardiovascular, circulatory and immune systems. To test the immune system, some crew members had blood drawn during orbit. The blood was centrifuged and monitored for production of white blood cells, which are critical to fighting off infection. Preliminary results indicate that space flight slows the proliferation of these cells, a serious potential problem for astronauts facing a long trip to Mars or long- term staffing of a space station.

The astronauts' hearts and lungs were also monitored, since in zero gravity, the lungs change shape because gravity is no longer pulling them down. This, in turn, affects gas exchange within the lungs. Data on these and other tests are still being analyzed.

In addition to the seven human crew members, there were 29 rats and 2,000 jellyfish aboard. The normally bobbing jellyfish swam in circles in zero gravity. Jellyfish have gravity receptors analogous to organs found in the human inner ear. By examining the development of these jellyfish receptors in space, scientists hope to gain understanding of the adaptation of the human vestibular system to zero gravity, thereby gaining insight on space adaptation sickness.

Jernigan was one of three crew members aboard responsible for detailed knowledge of the orbiter's procedures and computer and electrical systems. The three had spent many simulator hours in disaster drills. The flight, by comparison, was calm. "The ride uphill," Jernigan said, "was very interesting. It's not so much the intensity of the acceleration as the duration -- eight- and-a-half minutes of accelerating at 17,000 miles per hour."

While in space the crew photographed land, water and clouds. "The views of Earth from orbit," Jernigan said, "are breathtaking . . . It's just a beautiful planet and the atmosphere is so thin, and it sustains life. When you get up there and you see it, you feel what a responsibility we have to take care of it. I was not a fervent environmentalist before I flew, but afterward I found myself with more of those leanings."

Jernigan will be returning to orbit in September on the next shuttle flight. Among other experiments, that crew will deploy an Italian-made laser-ranging satellite to precisely measure continental drift.

Space Lab Life Sciences Two will launch in two years. By then, full results of the testing done on Space Lab Life Sciences One should be available, and the next battery of tests can begin.


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