XPost: sci.military.moderated   
   From: schillin@spock.usc.edu   
      
   "Paul F Austin"  writes:   
      
   >As I said in another answer, a 1MT exo detonation detonated just above the   
   >atmosphere would deposit about 3MRad at GEO. That's gamma. The sun's   
   >emissions are dominated by electrons with a minority of protons. Electrons   
   >are relatively easy to shield against (high energy protons are not). As a   
   >result, flares and all, a GEO sat is designed to withstand about 35-50KRAD   
   >over life. A design margin of 2 or 3 is added getting you close to   
   >100-150KR.   
      
      
   OK, math time.  Your 100-150 kRad figure corresponds with my own experience   
   designing flight hardware.  But, one megaton in LEO giving 3 MRad in GEO?   
   Not buying it.   
      
   One megaton is 4.2E15 Joules.  LEO to GEO is about 3.5E7 meters, depending   
   on how we define "LEO".  One Rad is 0.01 Joules per kilogram of deposited   
   energy.  And typical shielding density for unhardened spacecraft electronics   
   is still on the order of 100 mils of aluminum, mass density of 6.85 kilograms   
   per square meter.   
      
   One megaton in LEO produces an integrated flux of 4.2E15/(4*pi*3.5E7^2)   
   or 0.27 J/m^2 at GEO.   
      
   If every erg released by the detonation is gamma radiation, with a spectrum   
   optimized for energy deposition just inside 100 mils of shielding, that gives   
   us 0.27 / (e * 6.85) = 0.0125 joules per kilogram at the target electronics.   
      
   A little over *one* Rad, not three million.   
      
      
   I do not see how prompt gamma or X-ray radiation from a nuclear detonation   
   can be anything more than a very local hazard to satellites.  The 100-kRad   
   level will be reached only at distances of a hundred kilometers or so.   
      
   A high-altitude nuclear detonation can be a global hazard to satellites in   
   *Low* Earth Oribit, but that's from the high-energy electrons, in part due   
   to magnetospheric trapping (a short-lived but intense Van Allen belt) and   
   in part due to atmospheric interaction producing an electromagnetic pulse.   
   The former isn't even limited to line-of-sight; one well-placed large nuke   
   can take out every unhardened *LEO* bird.   
      
   But the very same magnetospheric trapping protect the GEO birds from that   
   effect.  And the numbers just don't add up for prompt X-ray/gamma.   
      
      
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