Cosmic Radiation

--- In spacesettlers@yahoogroups.com, Andy Goddard
> Oops...belay my last comment...my early morning tea has just
kicked in.
> Yes, twice the protection that you get from the atmosphere... so
8m of
> concrete/stone, 20m of ice...
>
> Regards,
>
> Andy G

Don't be so quick to belay that comment. This was bothering me too,
(actually it was knawing away at me, LOL) but I just couldn't figure
out what was bugging me about it and why I've never seen mention of
this.

Then it occured to me that this "Earth blocking" feature presupposes
that the Earth's atmosphere on the other side of the world doesn't
exist. If the atmosphere above your head blocks the radiation, so
too does the atmosphere down under. The Earth's bulk blocks the
radiation that has reached the Earth's surface from reappearing
across the diameter of the Earth, thus the amount of radiation it
blocks is miniscule, and should be factored out of consideration.

The figures I quoted in the previous post should all be halved, so
that you need 1.625 meters of shielding, and in an Island 3 the
atmosphere by itself should be sufficient because at 2.11 meters of
regolith equivalent, it would exceed the 1.625 meters.

Literature on the subject of radiation shielding always quotes about
2 meters of regolith whether in Habitats or on the lunar surface. It
seems that they've properly taken matters into account and have done
the full mathematical modeling of atmospheric density right up past
the stratosphere into the mesosphere which begins at 70 km.

TangoMan