How much radiation?

In article , bw wrote:
No, the highest exposure on an Apollo lunar expedition was a skin dose of
1.14 rad on Apollo 14...

Ok. The number that was in my head was "14" What I thought remembered was
the listing of all Apollo flights and that just one flight had a higher
exposure than all the others.

Yep. For some reason -- unfavorable trajectory or bad solar activity --
Apollo 14 got two or three times the average dose of the other Apollos.

I'll look up NCRP-98.

I see NCRP is online now, at http://www.ncrponline.org/, but by the
looks of it, their reports are still paper-only and still cost money.

NCRP-98 specifically recommends astronaut career limits based on a 3% risk
of excess cancer mortality -- roughly comparable to the lifetime risk of
fatal accidents in moderately-dangerous occupations...

Much better answer than mine, thnx. How is "3% risk of excess cancer
mortality" quantified?

We now have a fair idea of how the probability of radiation-caused cancer
scales with effective dose, mostly from the ongoing studies of the
Hiroshima and Nagasaki survivors. The one tricky part is converting from
absorbed dose (which is physics) to effective dose (which is biology) --
going from rads to rems in traditional radiation units, or grays to
sieverts in SI -- which is different for different types of radiation.
The exposure limits are currently in sieverts.

I'm sure that statistics are involved and that the "3%" part was decided
politically.

NCRP is a scientific group, not a political one. There may have been some
politics in the choice of the exact number, but there's a long pattern of
radiation standards being set based on risks in moderately-dangerous
non-radiation occupations(*) -- whose range is around 2-5% -- so 3% is not
grossly out of line.

(* "Moderately dangerous" means a job with significant on-the-job risk,
e.g. construction or agriculture, but excluding the really high-risk ones
like lumberjack or deep-sea fisherman or test pilot. )
--
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-- George Herbert |