From: cdorrough@nortonconsultants.com   
      
   "sanman"  wrote in message   
   news:f144e162.0403310605.1e379ab8@posting.google.com...   
   > henry@spsystems.net (Henry Spencer) wrote in message   
   news:...   
   >   
   > > Neither.  At present, both are of interest only for specialized military   
   > > applications.   
   >   
   > Well, perhaps the desire for rapid intercontinental travel will   
   > generate more interest in commercial development.   
   >   
   > > And neither has much to do with spaceflight.  Rockets are the technology   
   > > of choice for that.   
   >   
   > I thought that scramjets can help to achieve a good part of escape   
   > velocity, with some supplementary rocket thrust required to achieve   
   > orbit. I've read that PDEs can also be adapted for rocket propulsion,   
   > perhaps as part of combined-cycle engines, as might scramjets.   
      
   I'm no expert, but I think you might have got caught up in the emotion of   
   all this and overlooked a couple of minor points:   
      
   1.  Supersonic Combustion (SC) Ramjets only work at *supersonic* speeds...   
   and aren't much good either side of that speed (around Mach 7 it seems)   
   either.  Cruising at Mach 7 for a bit, is certainly no way to get to orbit.   
      
   2.  You have to *get* to the right speed first, before you can use it.  This   
   makes scramjets great for ICBM's (hell, at that speed you wouldn't even need   
   a warhead! ;-) and lousy for passenger transport ("hang onto your hats   
   folks!" ;-).   
      
   As for PDE's?  Well...   
      
   Cameron:-)   
      
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