Gravity Tests Prove Jarring for Discovery Astronauts : Space: Crew members spin in chairs and ride a sled. They receive electric shocks in an effort to study muscular response.
Astronauts aboard the space shuttle Discovery were spun around in a chair, pushed along a sled and even shocked Thursday to help scientists learn more about the most pervasive force in all of nature--gravity.
The rigorous tests were apparently taking their toll among the seven astronauts, some of whom were believed to be suffering from space sickness. But officials said the illness, which afflicts about two-thirds of all those who fly in space, was not having an effect on their research into the force that keeps the rest of us on the ground.
Gravity is the force that causes a tiny pin to fall, and it is the force that causes giant galaxies of billions of stars to spiral around their cores. Gravity is hard to study, said Ronald J. White, program scientist for Discovery’s International Microgravity Laboratory, “precisely because it is everywhere.”
Laboratories aboard the space shuttle, which is orbiting 185 miles above the Earth, give scientists a chance to study gravity by, in effect, removing it. They can’t get rid of it entirely, since gravity pervades the entire universe, but they can reduce it to the point that it nearly disappears. Scientists refer to the conditions in space as “microgravity.”
On Earth, gravity’s influence is so extensive that “your muscles and bones are the way they are because of gravity,” White said. They have developed in such a way as to allow us to stand erect and defy gravity, at least for awhile.
When gravity is removed, even the tiny organ called the otolith within the inner ear, which allows us to maintain a sense of orientation, no longer functions properly, thus causing some of the astronauts to experience something very similar to sea sickness.
In tests aboard the shuttle Thursday, crew members took turns riding a small sled. As the sled moved back and forth it stimulated the otolith organ. Then, small electric charges were applied to the back of the astronauts’ knees to see how the stimulation--or disorientation--affected their muscular response to the shocks.
That may not be a grand way to spend the day, but the results should eventually help scientists better understand how gravity influences something as basic as muscular response.
Gravity also influences just about everything else, such as the formation of organic compounds, and the orbiting laboratory allows scientists to remove gravity and change the way various compounds interact. Just as light oil separates at the top of a pool of water because of gravity, heavier molecules tend to sink lower in fluids, gases and solid objects.
Thus gravity distorts some substances, such as crystals used in powerful computers, and scientists hope to use orbiting laboratories to grow crystals that are much more symmetrical--and thus more useful--than those that can be grown on the ground. Several experiments aboard Discovery involve the growth of crystals.
Other experiments address one of the brightest prospects for future orbiting laboratories. The removal of the influence of gravity makes it easier to separate some materials, such as cells, from others, so it may be possible to extract extremely pure substances for use in pharmaceuticals. One experiment aboard Discovery is aimed at creating a very pure compound for use in cancer treatment.
Between medical tests, the seven astronauts tended to a slew of organisms carried into orbit for research, including roundworms, fruit flies, stick insects, frog eggs and sperm, fetal mouse bones, slime mold, yeast, wheat and oat seedlings, lentil roots, bacteria and billions of single cells.
The astronauts got a closer-than-expected look at the fruit flies. Some of the flies escaped from a cage, but were trapped in a glove box and removed by suction.
All but two of the 42 primary experiments are now under way, and the remaining two will be started soon, officials reported.
So far this has been one of the most trouble-free flights in years.
“We have no problems to report,” flight controller Wayne Hale reported late Thursday.
The shuttle, commanded by Ronald J. Grabe, 46, is scheduled to land Wednesday at 8:06 a.m. PST at Edwards Air Force Base in Southern California. Other crew members are Stephen S. Oswald, 40, the pilot; Norman E. Thagard, 48; William F. Readdy, 39; and David C. Hilmers, 41, all NASA astronauts; Roberta L. Bondar, 46, of the Canadian Space Agency and Ulf D. Merbold, 50, of the European Space Agency.
