XPost: sci.space.policy, sci.physics   
   From: jfindley@cinci.nospam.rr.com   
      
   In article ,   
   jfmezei.spamnot@vaxination.ca says...   
   >   
   > On 2018-06-22 07:18, Jeff Findley wrote:   
   >   
   > > Because it's flexible, duh.  Imagine that you took 10 meters of fishing   
   > > line with a weight at the bottom then cut it in the middle.  Would it   
   > > stay straight as it fell?  Try it!   
   >   
   >   
   > This does not consider/test the issue that the top of the cable is   
   > travelling at faster speed and as it is being pulled down, will   
   > accelerate further.  If the top of the cable wants to travel faster than   
   > the bottom part of cable, a tension will exist which would not exist in   
   > your fishing line example, and that tension should keep the cable straight.   
      
   Depends a lot on exactly where it breaks.  Also the drag from the   
   atmosphere of earth makes the dynamics a lot different than on a mostly   
   airless planet like Mars.  Look again at the simulations and research   
   papers on this subject that are online.   
      
   > > Why did the Tacoma Narrows Bridge break up due to *wind*?   
   >   
   > That cable would have to travel over 38,000km in vacuum before it got to   
   > atmpsphere.  So the top of cable (assuming breal at geostationary   
   > altitude) wouldn't have wind gusts at resonnance frequency.   
      
   That's not what I meant.  I meant that you can't know these things   
   intuitively.  The example was a huge bridge made of concrete and steel   
   that was destroyed by wind.  That's not intuitive!   
      
   You have to do the engineering analysis on these things.  Again, look at   
   the research that's already been done.   
      
   Jeff   
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