From: teeks99stuff@yahoo.com   
      
   "Alfred Montestruc"  wrote in   
   news:1110872035.543253.75340@g14g2000cwa.googlegroups.com:   
      
   > How much is needed and of what type?   
   >   
   > It seems obvious to me that the earth has enough radiation  shielding   
   > at sea level or even at say 12,000 feet above sea level to protect   
   > people from pretty much the worst that we can expect.  That implys   
   > about 10-14.7 pounds-mass per square inch of surface area of the   
   > habitat in light elements like Oxygen and Nitrogen or Hydrogen, and   
   > perhaps more of other materials.   
   >   
   > H2O ice, or perhaps liquid water, or perhaps various plastics might   
   > make good materials for this with perhaps nickle steel or aluminum   
   > structural backing.   
   >   
   > This winds up being about 23.1 to 33.92 foot thick ( 7.03-10.34 meters)   
   > of liquid water.   
   >   
   > Is this a reasonable approximation? Or does someone have a better   
   > reference with hopefully less massy shielding ideas?   
   >   
   > I am aware that this much will not be needed all the time, but even for   
   > a radiation shelter this is pretty heavy.   
   >   
      
   If I'm correct, a lot of the (harmful) radiation from the sun is trapped by   
   earth's magnetic field, even before it gets to the atmosphere.   
   Maybe it would be possible to also produce a magnetic field around the   
   spaceship, in addition to the above mentioned water/plastics. (I have no   
   idea how strong the magnetic field is, this might not be possible at all).   
      
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