Life Support Systems
Section 4.3.5.
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Low-gravity Deconditioning and Long-duration Human Spaceflight

A frequent worry of planners of permanent human presences on the Moon is the prospect of people living in the moon deconditioning to the point that they would be unable to adapt to full Earth gravity.

We don't know for sure if this will be a problem, but we do have some applicable data which indicate that although deconditioning is a very real phenomenon, it most likely will not mean someone could never return to Earth.

People have lived for more than a year in zero-g. Those cosmonauts had to be carried off their spacecraft, but they did recover their musculature and most (not all) of the bone mass. After a few weeks, the rate of deconditioning drops off to become immeasurable, so the experience with year-long space flights is probably indicative of decades-long space flights.

NASA and the Russian Space Agency are still experimenting with the effects of different exercise techniques to reduce deconditioning. They're especially worried about a Mars flight. We wouldn't want a Mars crew to arrive at the red planet unable to explore. (On the other hand, if they have to be met by stretchers back at the home port, who cares? Let them get some well-deserved sack time once they get back.) When the data come back from the Shuttle flight that just landed, the doctors will be a lot smarter on this issue. And of course the body of experience from Mir continues to grow.

For the lunar community, the biggest question in my mind is the effect of low gravity on people actually born on the moon. Will they naturally develop demineralized bones, weak muscles, and a wimpy cardiovascular system? We have no experience with this, and not much in the way of life sciences data from animal studies.

The good news is that in about two years, we'll have the International Space Station's laboratory operating. There we can get some really long-term rigorous biomedical data.

Life Support Systems

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