Radiation Exposure

>
> I have a question I have been mulling over regarding the risk of
> radiation exposure. In his book "High Frontiers", Professor O'Neill
> states that the most serious cosmic-ray problem is prolonged exposure
> to "heavy primaries" and that on Earth, the atmosphere provides
> protection against them. He further states that the only direct human
> experience with heavy primaries has been that of the Apollo
> astronauts. I am curious as to why other astronauts (Gemini and
> Skylab at the time of publication, and certainly Shuttle and MIR
> since, for example) have not had experience with heavy primaries as
> they have spent extended time outside of the atmosphere's protective
> cover.
>

The protection isn't the atmosphere, but the Van Allen radiation belts
around the Earth (except near the magnetic poles). Low Earth orbit, which
is as far as all our non-Apollo astronauts have gone, is within the
innermost belt, and so avoids direct exposure to these.

The "heavy primary" radiation threat is somewhat different from
ordinary radiation exposure here on Earth - the only real analog
is putting yourself in the beam of a heavy-ion accelerator; we have
a local research group that's part of a NASA institute that's
been studying this sort of thing:

http://www.nsbri.org/ (National Space Biomedical research Institute)
http://www.nsbri.org/Research/Radiation.html (Radiation Effects)

Arthur