XPost: sci.space.policy   
   From: joe@strout.net   
      
   In article <1153042609.617603.12360@m73g2000cwd.googlegroups.com>,   
    "Kent Paul Dolan"  wrote:   
      
   > Mike Combs wrote:   
   >   
   > > I've lost count of how many times on these   
   > > newsgroups I've encountered someone saying that   
   > > providing space habitats with natural sunlight via   
   > > mirrors and windows would just be too complicated,   
   > > and we'll instead use artificial illumination.   
   >   
   > Since I haven't seen this mentioned yet, a third   
   > option would be to use fiber optic piping to feed in   
   > the light.   
      
   That's not practical except over very short distances.  I was recently   
   reading about this actually being put to use in real buildings -- light   
   collectors on the roof, fed to fiber optics, which then light up glow   
   tubes right next to the fluorescent lights.  Light sensors automatically   
   shut off the fluorescents when the piped light is bright enough.   
      
   However, the losses in the fiber optics are pretty severe -- IIRC, both   
   because of the wide bandwidth of the light, and because of its   
   intensity.  I regret that I don't have the figures handy, but the upshot   
   was that this was considered impractical for anything but the top floor   
   of the building.  (Which made me wonder at the time: why not just put in   
   windows instead?  ...But I guess the point was that this could be   
   cheaply retrofitted into existing buildings.)   
      
   > No energy to energy conversions would be needed, so   
   > losses of the gathered light would be minimal.   
      
   This is the incorrect part.  Light losses in the fiber optic cables will   
   be severe.  (And of course, all that lost light gets turned into heat,   
   that your colony then has to reject.)   
      
   Best,   
   - Joe   
      
   --- SoupGate-Win32 v1.05   
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