From: g_d_pusch_remove_underscores@xnet.com   
      
   "Maarten"  writes:   
      
   > After browsing the internet for some time, I still haven't found an answer   
   > to the following question.   
   > As a novice in this area, I wonder why there is such a specific preference   
   > for having e.g.  ISS, Space Shuttle  in an orbit of about 400km. (This I   
   > make up from the testimonials from space ships' crew that all tell about the   
   > sun coming up and going down every 1.5 hours).   
   > So my question is, why this preference for 400 km and why isn't it an orbit   
   > of 250km or 600km or even more ?   
      
   Too low an orbit and there is too much air drag on the spacecraft, so that   
   its orbit decays too rapidly.   
      
   Too high, and it gets into the lower fringes of the van Allen radiation belt,   
   which is not healthy for either the crews or the electronics.   
      
   Finally, 90 minutes divides evenly into 24 hrs, and it might be operationally   
   convienient for there to be roughly an integer number of orbits per workday...   
      
      
   -- Gordon D. Pusch   
      
   perl -e '$_ = "gdpusch\@NO.xnet.SPAM.com\n"; s/NO\.//; s/SPAM\.//; print;'   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)