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  1. Newsgroups: sci.space
  2. Path: sparky!uunet!haven.umd.edu!darwin.sura.net!mips!sdd.hp.com!cs.utexas.edu!torn!utzoo!henry
  3. From: henry@zoo.toronto.edu (Henry Spencer)
  4. Subject: Re: SPS fouling astronomy
  5. Message-ID: <Bsw0uw.Ho7@zoo.toronto.edu>
  6. Date: Wed, 12 Aug 1992 20:28:06 GMT
  7. References: <1992Aug07.172531.129551@cs.cmu.edu> <63732@cup.portal.com> <20618@sbsvax.cs.uni-sb.de> <1992Aug12.044959.19501@dartvax.dartmouth.edu>
  8. Organization: U of Toronto Zoology
  9. Lines: 16
  10.  
  11. In article <1992Aug12.044959.19501@dartvax.dartmouth.edu> Frederick.A.Ringwald@dartmouth.edu (Frederick A. Ringwald) writes:
  12. >...issue of COST is unresolved, however, but come to think of it, is there
  13. >any reason SPS *must* be a mega-engineering project? Might there be
  14. >some way of doing it simply?
  15.  
  16. Unfortunately, if you use microwaves there is a fundamental problem:  to
  17. keep the size of the receiving rectenna manageable, you *must* have a
  18. transmitting antenna on the order of a kilometer wide, assuming your
  19. bird is in Clarke orbit.  (An order-of-magnitude approximation is that
  20. the product of the antenna radii must exceed distance times wavelength.)
  21.  
  22. Laser transmission would scale down better, but runs into the weather
  23. problem, which microwaves largely avoid.
  24. -- 
  25. There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
  26. mistakes, but... make *new* ones. -D.Sim|  henry@zoo.toronto.edu  utzoo!henry
  27.