On Friday, March 17, 2017 at 3:11:33 AM UTC-5, Greg Goss wrote:   
   > In one of the Ringworld novels, Either Louis or someone explaining to   
   > Louis points out the truly humungeous amount of hydrogen that would   
   > have been consumed spinning up the artifact.   
   >    
   > Bussard Ramjets are canon in this series, and were used by the   
   > builders of the Ringworld.  So you have a humungeous supply of   
   > hydrogen in the solar wind.   
      
   Do we?   
      
   In absolute terms, how much hydrogen is the star throwing off?  How long do   
   you have to wait for it to spray out enough hydrogen to spin up the Ring?    
   IIRC, the kinetic energy of the rotating Ring (which was spinning at .004c and   
   massed the same as    
   Jupiter.  That's a lot of energy, so we're going to need a lot of hydrogen.   
      
   Remember that we can't capture all the solar wind unless we through a true   
   Dyson Sphere around it, too, so whatever we capture is only a fraction of the   
   total.   
      
   A Bussard drive works (or at least it works in fiction) because the ship is   
   moving close to the speed of light and the intake-field sweeps out a huge   
   swath of space in a unit of time.  That wouldn't apply to the attitude jets of   
   Ringworld.   
      
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