From: jeff.findley@ugs.nojunk.com   
      
   "Paul F. Dietz"  wrote in message   
   news:xKadnTNdpO0hr6vfRVn-sw@dls.net...   
   > Tom Clarke wrote:   
   >   
   > > Could the "water" jet be used to push a comet into earth orbit?   
   >   
   > You get a much better Isp by turning it into steam -- and you   
   > can use lower cost thermal energy instead of more expensive   
   > mechanical energy.   
      
   If the comet is close enough to the sun when you do this, you can use cheap   
   solar energy to power your engine.  Mirrors can focus sunlight on your   
   rocket engine chamber, so the design would hopefully be fairly simple and   
   inexpensive compared to the equipment to power a water jet.   
      
   Jeff   
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