From: fmccall@earthlink.net   
      
   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.   
      
   --   
   "The reasonable man adapts himself to the world; the unreasonable   
    man persists in trying to adapt the world to himself. Therefore,   
    all progress depends on the unreasonable man."   
                                         --George Bernard Shaw   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)