From: monte.davis@verizon.net   
      
   "Mitch"  wrote:   
      
   >Why would one not   
   >use something like a modified commercial airliner (make it airtight and   
   >so forth) and then perform a regular take off and fly up to the   
   >altitude where the air still supports the lift on the wings (using   
   >plain old kerosene) and then once that barrier has been reached utilize   
   >a rocket engine to make it the rest of the way.   
      
   I'm sure you'll get much more detailed answers, but the simplest one   
   is that an aircraft's ~10 miles isn't that much of a head start on the   
   100+ miles for orbit -- and much more importantly, an aircraft's ~500   
   mph *really* isn't much of a head start on the 17,000 mph needed for   
   orbit.   
      
   The idea is seductive, going back to Eugen Sanger in the 1930s; it   
   seems reasonable on the face of it to "evolve" gradually from air   
   travel to space travel. But subsonic, supersonic, and hypersonic   
   flight are very different aerodynamic regimes as far as design for   
   lift, drag and collection/compression of engine air is concerned. And   
   the turbojet that works well from subsonic to Mach ~3 is not the same   
   as the ramjet that might make more sense around Mach 5-6, or the   
   scramjet that looks best above Mach 8.   
      
   Bottom line: the tempting simplicity of the space plane idea starts to   
   get dauntingly complex as you get into the engineering.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)