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Experiment gauges astronauts' effects

As they go about their daily activities -- and even play darts -- crew members aboard the Russian space station Mir are participating in an experiment designed by MIT engineers.

The results will give researchers a better understanding of how crew members physically affect their environment and how they adapt to zero gravity. Data from the former part of the experiment could save millions in the design of future space structures like the scheduled international space station. Currently there is very little data on the forces astronauts exert on spaceships, so engineers over-design the racks housing sensitive experiments that could be disturbed by astronauts' movements.

The experiment, led by Assistant Professor Dava J. Newman of aeronautics and astronautics, was launched to Mir in late April and was activated May 10. It will continue through December, possibly longer if funding permits. During this time up to nine astronauts and cosmonauts will participate.

Professor Newman conducts training sessions for the experiment with all of the crew members involved. Recently she returned from Russia, where she trained the two cosmonauts and one astronaut who will relieve those currently aboard Mir in August.

Key to the experiment are specially instrumented footloops, a handhold and a push-off pad. Data will be collected on the forces applied as crew members use these sensors to get around or anchor themselves. The researchers are also interested in how frequently those forces are applied.

This is the second flight for the experiment; the first, in 1994, was aboard the space shuttle Columbia. That flight yielded the first data on the forces associated with astronauts' everyday activities, and showed that previous estimates of those forces were off by an order of magnitude.

"We found that each astronaut had an average force value of 28 newtons, "Professor Newman said. In contrast, "for the space-station models they're still using 800 newtons for crew input. So we're showing them an order of magnitude reduction with our data."

The larger estimates were based on studies in the 1970s with astronauts aboard Spacelab. Those studies, however, represented the extreme. "For example, the astronauts were pushing off one wall and soaring to another wall as fast as they could," Professor Newman said. "We are measuring the forces associated with everyday, common activities."

Results from the current experiment, dubbed Enhanced Dynamic Load Sensors (EDLS), will add to the pool of data on how astronauts affect their environment. For the first time, the researchers will also correlate crew forces with spacecraft acceleration. This "will allow us to start piecing together the overall picture of what is happening up there," Professor Newman said.

In addition, the researchers plan to study crew members' motion in zero gravity and how they adapt to weightlessness. "We're interested in looking at changes in human motor control in different gravity environments," she said.

To do so they will videotape crew members as they play darts. With the help of four cameras, "I can basically trace out the entire arm motion so we can get three-dimensional data," Professor Newman said. "We'd like to have them do this part of the experiment as soon as possible after they've arrived on Mir, then at the middle and end of their time there. That way we should get rich data on how they adapt to their new environment."

Other engineers involved in EDLS are Professor Edward F. Crawley. Dr. Marthinus C. van Schoor, a lecturer, and Michail Tryfonidis, a graduate student, all in the aeronautics and astronautics. Sherwin Beck of NASA's Langley Research Center is a co-investigator and technical monitor of EDLS. Payload Systems, Inc., of Cambridge built the hardware for the experiment. The work is funded by NASA.

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A version of this article appeared in MIT Tech Talk on June 5, 1996.

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