From: jcyclespersecondlongisland@nine.reticulatedcom.com.retro.com   
      
   On 9 May 2004 07:45:42 -0700, Mike Miller  wrote:   
      
   > The hoop stress in the sphere would be a piddly 29000psi, well within   
   > the range of metals to resist. Pure aluminum is almost up to the task.   
   > That stress should increase linearly with increasing radius of the   
   > vacuum balloon, assuming wall thickness stays the same. By 60m, you   
   > should have a lot of net lift.   
      
   We're not dealing with tensile strength, we're dealing with resisting   
   buckling.   
      
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