From: henry@spsystems.net   
      
   In article ,   
   sanman  wrote:   
   >> ...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.   
      
   Not likely.  Engines are not the bottleneck in the development of rapid   
   intercontinental travel.  In the past, studies of this have generally   
   concluded that the point of diminishing returns sets in around Mach 5 or   
   so:  beyond there, the shortening of travel time no longer buys you as   
   much, the technology becomes more and more problematic, and the necessary   
   changes in infrastructure (e.g. facilities for new fuels) start to become   
   very costly.  Turboramjets should be adequate to go that fast.   
      
   >> 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.   
      
   The question, always, is not whether it can be done, but whether it's   
   actually *better* than just making a rocket's tanks bigger.  Replacing   
   simple tanks of liquid oxygen with heavy, complex high-tech machinery   
   which requires flight in extremely hostile aerothermal conditions is most   
   unlikely to be a net win.   
      
   "Throwing away the LOX tanks on a launch vehicle is very nearly the   
   stupidest possible design decision ever." -- Christopher M. Jones   
      
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   MOST launched 30 June; science observations running     |   Henry Spencer   
   since Oct; first surprises seen; papers pending.        | henry@spsystems.net   
      
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