"Dr. O" wrote in message
...
http://www.nytimes.com/2003/12/09/sc...ce/09RADI.html

The thing I don't understand is that people have been spending much more
time in orbit than the round-trip to Mars. Although the upper atmosphere
does shield them somewhat, the majority of the radiation is still getting
through. Why are they so concerned then about radiation?

Also, lead shielding will have to be installed in any Mars spaceship
anyway
because of the possibility of solar flares.


As to the shielding, I suspect it will be a plastic or part plastic.
If it contains lead or other heavier metal, they will be on the outside.
And the low density materials will be on the inside.
Read up on "graded shielding" for radiation.

When high energy particles and high energy photons strike
a thin dense shield, they liberate a "spray"
of other particles and photons.While the spray will have
somewhat lower energy, the beta particles will
have higher linear energy
transfer. In short, a thin shield of a relatively dense
material even as humble as aluminum may result in a
higher radiation dose to the space traveler.
The inner plastic layer would absorb the betas and
soft gammas and x-rays.

My ideal for sheilding would be to have such a large
space ship that a outer wall could like that on a battleship
and still have a low overall density of structure not including
the fuel. I know, I am dreamer.

sleeeppy...............................William A. Noyes