From: timothyellrod@live.com   
      
   On Wednesday, October 4, 2017 at 3:39:10 PM UTC-4, Ian Sturdy wrote:   
   > All those radiators seem to be operating at rather low temperatures--if you   
   could run at 2900K instead of 1450K, you would only need 1/16th the radiator   
   area. I expect a beryllium phase-change radiator would operate close to its   
   boiling point of 2742K,    
   giving a sizable advantage. Given also that the molybdenum/lithium radiator is   
   four times the weight per heat capacity as the best radiators on that page,   
   which also operate at low temperatures, I would not be surprised if much   
   better were possible.   
   >    
      
   That thought did occur to me.  Since the Mo/Li heat pipe radiator operates at   
   90.455% of lithium's boiling point, I ran the numbers for a radiator operating   
   at the same percentage of beryllium's boiling point (this came out to about   
   2,480 K).  Needless    
   to say, that cut down on the radiator area by A LOT.   
      
   > I also expect your 20% estimate to be high--the trick in fusion engines   
   seems to be running the fusion reaction very far from any solid components.   
   The Firefly certainly seems to be designed around that, with the very narrow   
   body and conical tail    
   minimizing its apparent aspect. Moreover, 50% of your waste heat is x-rays,   
   which will not be completely absorbed by small thicknesses of matter.   
      
   True.  I reduced it to 10%, which needless to say also reduced the radiator   
   area.  Granted, that might STILL be too high, but I don't want to guess too   
   low either.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)