"John Schilling" wrote in message
...

Solar flares
and similar events are associated with intense, lethal radiation, but this
lasts only a few hours and can be detected at least half an hour in
advance.

Could you clarify this. I understood that peak radiation occurs in a short
period but that increased radiation can be present for a longer period even
days. Also, what infrastructure would be needed to provide detection,
verification and notification to travellers with a half hour advance
warning. I understood that minutes warning was the more likely scenario and
that is assuming a successful detection with significant infrastructure.

So retreating to a small, shielded enclosure for the duration is an quite
reasonable solution. And the level of shielding required, is fairly
modest.
Just packing all your crew's food and drinking water around yhe shelter,
for example, would suffice.

Of course if your talking about a few food bars and a couple of bags of
water for the trip to the moon this is highly unlikely to offer any real
protection. Additionally, given these are consumables, wouldnt you also need
to incorporate your waste streams into such a protection, otherwise your
likely to be on a ever increasing radiation environment as you consume food
and water.

Somewhat more worrisome is *cosmic* radiation. This is much more
energetic,
requiring something like half a meter of lead to stop, and it is a steady
bombardment rather than a series of predictable bursts.

I thought lead was a terrible radiation shield and compared poorly with
hydrogen rich materials. Would half a meter of lead really stop the
energetic particles or simply transform them into radiation of a more life
threatening kind.

If you can't shield
your entire habitable volume with that half-meter of lead or the
equivalent,
you just have to take it. And while it is not intense enough to be an
acute
hazard, a year's exposure would be associated with a ~3% increase in
lifetime
cancer risk.

Are you sure about this. What age group are we talking about, what exposure.
A 18 year old male sitting in a apollo capsule for a year is going to have
significantly more than a 3% mortality increase assuming he even survives at
all. Are you sure your not referring to LEO radiation as opposed to the
Space Environment.

So we'd like to block the cosmic radiation if we could.

Sure, which I would think, cover you for any Solar events as well.