XPost: sci.space.policy   
   From: dietz@dls.net   
      
   Phil Paisley wrote:   
      
   > Apart from higher energy upper stages, which seem to be part of the   
   > Delta IVs future at least, isn't there a way to tweak the specific   
   > impulse of the RS-68 even a little bit?  I believe the H-1 and the F-1   
   > were both incrementally upgraded over the course of their lives with   
   > considerable payoffs in lofting capacity.   
      
   You could use FLOX :).  But I doubt that works well in a hot-oxidizer   
   staged combustion cycle.   
      
   Maybe gelled metalized RP-1 for the fuel?   Adds about 5% to the Isp.   
      
   	Paul   
      
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