From: junkmail@wolfkeeper.plus.com   
      
   Henry Spencer wrote:   
   > In article ,   
   > Ian Woollard   wrote:   
   >   
   >>>It could only work for that short period of time the craft was still in   
   >>>useful air.   
   >>   
   >>Clearly, however the ISP over that time is extremely high for a solid,   
   >>and reduces the GLOW of the vehicle quite a bit...   
   >   
   > And we care about that... why, exactly?   
      
   Only because the GLOW suggested that the airbreathing was working. The   
   GLOW is reasonably unimportant, but ISP clearly isn't. Airbreathing for   
   a first stage (*not* an upper, orbital stage) is a much more respectable   
   concept, atleast two launchers use that- Pegasus, and SpaceShip One; and   
   several others, such as Black Horse (fuel would be lifted using a   
   transport plane) have proposed to use it. It was seriously considered   
   for the Space Shuttle and the N-1 IRC.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)