From: henry@spsystems.net   
      
   In article <58866faa.0402081041.4c4dde36@posting.google.com>,   
   Zoltan Szakaly  wrote:   
   >You can have the H2 dissociate in the reactor core, absorbing energy   
   >and then have them recombine in the nozzle. This phenomena was studied   
   >in the 60s and may have been partially used in rover and kiwi. It   
   >takes a high temperature in the reactor core.   
      
   The assessment I saw -- a Bussard paper which may not have been   
   definitive, I haven't studied nuclear-thermal rockets carefully -- was   
   that for orthodox solid-core systems, hydrogen dissociation isn't very   
   useful because of the finite recombination rate and the rapid expansion   
   of gas in the nozzle.   
      
   If you run your engine at quite low pressure, which permits plenty of   
   dissociation, then after only a bit of expansion, the recombination rate   
   is too low for much to happen within the nozzle.  At higher pressures,   
   where recombination can occur much farther downstream, there's not much   
   dissociation.  Intermediate values suffer both problems.  Only if you can   
   run substantially hotter -- with a liquid-core reactor or perhaps an   
   unorthodox solid-core design -- can you achieve both substantial   
   dissociation and usefully rapid recombination.   
   --   
   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)