From: jeff.findley@ugs.nojunk.com   
      
   "jtingle"  wrote in message   
   news:s3dui1t55h9npevv0c6h43u03aq69cltgn@4ax.com...   
   > Short version:   
   >   
   > It might help slightly, but the added drag quickly eats up the   
   > advantage of not carrying oxidizer as speed increases in a vertical   
   > launch. In addition, modern jet engines are not designed to be at   
   > their best under these circumstances. You'd probably be better off   
   > with a big crude 1950's style engine than a modern turbofan. In   
   > addition, jet engines aren't disposable on the scale of minutes of   
   > operation, and it would probably cost too much to make it practical.   
      
   I wouldn't go all the way back to 50's style engines.  Any modern turbojet   
   (used in any modern jet fighter) would suffice.  For a demonstrator (e.g.   
   DC-X like vehicle), you could use turbojets from just about any retired jet   
   fighter.   
      
   The advantage here is that you can use proven turbojet technology to create   
   a reusable first stage that's far cheaper to operate than your typical   
   expendable rocket powered first stage and goes faster and/or higher than air   
   launch from a jet aircraft.  True the performance may not be all that great   
   by rocket powered first stage standards, but it's far better than air launch   
   from a jet aircraft, and the cost may not be that much higher than using a   
   carrier aircraft since it's using much the same technology (turbojets).   
      
   Jeff   
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