We don't talk about human spaceflight too much on this blog. But I couldn't resist weighing in on this discussion on BBC about the merits of centrifuges for inducing artificial gravity . Get it? Weighing in?
To some, it's "obvious" that creating a centrifugally-induced artificial gravitational field will mitigate the health effects of weightlessness. To others, maybe not so obvious. The BBC article itself talks about "theories" of how this could benefit long-duration space travelers.
About 50% of all astronauts get space sickness. One of the most comprehensive and comprehensible accounts is in the marvelous "Packing For Mars" by Mary Roach. And these are ASTRONAUTS. But more worrisome is the bone mass loss that seems inevitable in zero-g. Roach tells us that you might be able to exercise your way around much bone loss, as Commander Peggy Whitson did on her first ISS trip. But this increases oxygen and food consumption--is that really a good thing?
Perhaps a centrifuge is the answer. But how many hours a day in the artificial gravity of a centrifuge would be enough to mitigate health effects? How much difference might it make that the gravitational field at the astronaut's head is different from the one at her feet? That's called the "tidal force," by the way--a change in field over a relatively short distance.
The most important experiment ever conceived for the International Space Station was the centrifuge experiment. It hasn't been done, for whatever reason. Until it is done, one of the greatest risks of a long space voyage (the other being radiation damage) is still not understood.
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