Absence of Gravity Weighs Down Future of Long-Term Spaceflight

FOR Marsha Ivins, adapting to life on the latest space shuttle mission has been ``a great face lift.'' She says she felt ``all sorts of things happening the first few days,'' including a shift of body fluids to her head, which puffed up her face, and a sense of balance gone ``a little goofy.''

Such are the rigors of weightlessness that astronauts and cosmonauts take in stride. They raise the biggest uncertainty in spaceflight: Is the body's adaptation to weightlessness manageable, or will it prevent long-term missions?

Space physiologists take every chance to look for answers. That's why Ms. Ivins and her four fellow astronauts on the Columbia shuttle mission have given each other physiological tests, taken blood samples, and tried out a lower-torso vacuum bag. The latter is a test to see if the partial vacuum the bag creates will draw body fluids down where they should be in a physiological system that has evolved under Earth's surface gravity.

To put the challenge in perspective, Claude Arnaud of the University of California at San Francisco notes that bone loss may be the biggest concern. During a recent meeting there of the American Association for the Advancement of Science, he explained that Russians ``have lost enormous amounts of bone'' during three-month tours on the Mir space station. Cosmonauts take about a year to recover from long spaceflights, he said.

BECAUSE of such experiences, the National Academy of Sciences has put a high priority on understanding bone loss. Dr. Arnaud said it conceivably could preclude long-term spaceflight. But he added: ``I hasten to say it's near solution,'' given research now focused on it.

Muriel Ross of the National Aeronautics and Space Administration Ames Research Center in Mountain View, Calif., said at the conference that changes to the nervous system are also a puzzler.

She and Arnaud are participating in shuttle missions devoted to life-science research. They based their comments partly on results from an initial June 1991 mission and are working up results from an October flight.

They also look forward to research on the international space station and to working with Russians on Mir. They said they want to have a centrifuge on board to simulate different degrees of gravitational strength and to evaluate it as a possible countermeasure to weightless-induced body changes. Bone loss ``is a very easy thing to prevent if you can produce a gravitational field in space,'' Arnaud said.