From: henry@spsystems.net   
      
   In article ,   
   aSkeptic  wrote:   
   >Would preheating the H2, to break it down to H, before it enters the   
   >combustion chamber improve a chemical rocket's "gas milage"/exhast   
   >velocity?   
      
   If you could do that... yes, very considerably.  You could forget the   
   oxidizer, and just let the H recombine to H2 -- an *IMMENSELY* energetic   
   reaction, which would not only make most other chemical rockets obsolete,   
   but would eliminate all interest in solid-core nuclear-thermal rockets.   
   Nothing short of gas-core nuclear could compete.   
      
   Trouble is, all that energy has to *come* from somewhere.  As you might   
   guess from the above, you need extremely high temperatures to break down   
   H2 to H.  This isn't some little add-on to the propulsion system; it   
   *becomes* the propulsion system.   
      
   Practical interest in such approaches centers on finding a way to   
   stabilize H, so you can invest all that energy on the ground, and release   
   it in flight without having to carry the powerplant along.  Unfortunately,   
   nobody has yet found any workable stabilizing technique.   
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   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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