From: cdorrough@nortonconsultants.com   
      
   "Fred J. McCall"  wrote in message   
   news:jnkru0d7jq9g7a11n3pvskhmsj2shjrn34@4ax.com...   
   > fairwater@gmail.com (Derek Lyons) wrote:   
   >   
   > :schillin@spock.usc.edu (John Schilling) wrote:   
   > :   
   > :>Also, this being sci.space.tech, one has to think in terms of using the   
   > :>scramjet as part of a space launch system.  In which case, you're going   
   > :>to need the rocket *anyway*, as scramjets can't get you more than half   
   > :>way to orbit.  If your scramjet space launch system absolutely has to   
   > :>include a rocket good for boosting halfway to orbit, and it does, you   
   > :>probably want to try real hard to use that same rocket to get up to   
   > :>scramjet operating speed from the start, rather than adding a third   
   > :>propulsion system to the mix.   
   > :   
   > :The real question is...  Why add a *second* propulsion system in the   
   > :first place?  If you need a rocket to get from to the scramjet range,   
   > :and then a rocket to get from scramjet range to orbital range...  What   
   > :is the scramjet adding?   
   >   
   > It's a question of whether the weight of the extra engines you need to   
   > carry is more than offset by the weight of the oxidizer you DON'T need   
   > to carry.   
   >   
   > So far, the general decision for most folks has been that it doesn't.   
   > Add in the extra complexity of an extra set of engines and it's a net   
   > lose.   
   >   
   > Not to say it will always be that way, though.   
      
   There has been quite a bit of research on all of this over the years that   
   make quite interesting reading.   
      
   Try a Google search on "rocket-based combined cycle" (RBCC)...   
      
   Cameron:-)   
      
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