From: henry@spsystems.net   
      
   In article ,   
     wrote:   
   >Would it be possible to use conventional jet engines to attain sufficient   
   >airspeed for scramjets to start to function?  SCRAMjets would seem to have   
   >limited value if they can only be launched via rocket.   
      
   It's conceivable but difficult.  In practice, you need a ramjet phase in   
   between.  You can add a limited ramjet mode to a turbojet fairly easily,   
   as witness the J-58 on the Blackbirds, but that might not be good enough.   
      
   The reason people are attracted to rocket launch for scamjets [typo   
   intentional] is that if you're trying to do orbital launch, you need a   
   rocket system *anyway*... whereas the turbojet and ramjet are pure dead   
   weight once you're past their fairly narrow speed ranges.  (A rocket   
   system used for takeoff is probably going to be bigger than really needed   
   for the final push to orbit, but rockets excel in getting a lot of thrust   
   out of compact, lightweight engines, so the penalty is not huge.)   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)