From: vince@offshore.ai (Vincent Cate)
Newsgroups: sci.space.tech
Subject: Re: Radiation shielding for hotel at GEO?
References: <9186edb5.0308081641.5036919e@posting.google.com>
NNTP-Posting-Host: 207.42.133.230

From "Space Stations and Platforms", Gordon R. Woodcock, 1986, page 46,47:

"Cosmic Rays

"Cosmic rays are very high energy particles that originate outside the 
solar system.  Their sources are not known but candidates include 
supernovae and high-energy processes associated with exotic phenomena 
such as neutron stars and black holes. The cosmic ray flux is far less 
intense than that of solar flares, or of particle fluxes in the Van 
Allen belts, but cosmic ray flux is continuous and shielding is 
impractical.

"Most of the cosmic ray particles are hydrogen and helium nuclei, but 
heavy nuclei are also present as shown in Figure 4.9.  Cosmic ray 
particles are bare nuclei, fully ionized.  The heavy nuclei carry 
high charge (Z) at high energy and are often called high-LET (linear 
energy transfer) or HZE (high-Z, high energy) particles.

"As these particles pass through the structural wall of a space station, 
their interaction with the wall usually causes incremental loss of energy
and charge, but very few are stopped.  Those that are usually create
cosmic ray showers; occasional head-on collisions with atomic nuclei 
in the wall result in both nuclei being shattered into many smaller, 
but still higher-energy, nuclear particles.  The net result is that the
radiation dose for the crew increases with shielding thickness up to a 
point of very thick shields.  Only extremely thick shields, on the 
order of hundreds of grams per square centimeter, are sufficient to 
reduce cosmic ray doses to values similar to Earth surface background.  
(The Earth's atmosphere provides about 1000 g/cm^2 mass shielding.)

"The Earth's magnetic field deflects cosmic rays as it does solar flare 
particles, but the most energetic cosmic rays are little affected.  
For a space station in low altitude, low inclination orbit, Van Allen 
radiation contributes most of the crew dose; solar flares contribute 
very little, and cosmic rays contribute somewhat more.