From: newsposter@andor.dropbear.id.au   
      
   On Sat, 2 Sep 2017 21:54:36 -0700 (PDT), johnny1a.again@gmail.com   
    wrote:   
   | Assume for a moment that an asteroidal object of metallic/rocky   
   | composition were to exist in the shape of a doughnut/torus, with   
   | a radius of half a mile _within_ the cylinder, that is, the 'ring'   
   | of the doughnut is 1 mile in diameter from the inner rim to the   
   | outer rim, and the hollow area in the middle is ~3.4 miles across.   
   |   
   | What I'm trying to determine is if this could hold its shape   
   | against its own feeble gravity over time, and if so, how much   
   | rotation could it handle before it deformed out of the torus shape?   
      
      
   I'm pretty sure the shape would hold up against it's own gravity. You   
   need to get up around 300km diameter before gravity make everything turn   
   into a sphere. On the other hand, a torus is a long way from a sphere,   
   so there better not be any major faults/cracks in the rock. Still your   
   torus is only ~8km across, so you are about 1/40th of the hard limit.   
      
   I have no idea about the rotation. Rock is no known for it's tensile   
   strength, so I doubt it would take much rotation to damage it. It would   
   also depend on what plane it was rotating in.   
      
   In an ideal situation, if it was rotating about the axis that was normal   
   to the plane of the ring, rotation would tend to cancel out gravity, if   
   the rate was carefully chosen.   
      
      
   --   
   Reverend Paul Colquhoun, ULC.     http://andor.dropbear.id.au/   
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