From: henry@spsystems.net   
      
   In article <1127135506.835715.74830@g14g2000cwa.googlegroups.com>,   
     wrote:   
   >Would it be feasible to use air breathing jet engines as the 1st stage   
   >(or as strap-ons) of a launch system?   
      
   Yes, but with the exceptions of air launch from an existing aircraft, and   
   systems which use the jets for some other purpose as well, using rockets   
   is better.   
      
   Jet engines and their air intakes are complex and heavy, work only over   
   limited ranges of speed and altitude, and are quite fussy about the   
   smoothness of the incoming airflow (which means you can't just hang them   
   on anywhere).  Rocket engines are light and compact, don't care about   
   speed or airflow, and work *better* as altitude increases.   
      
   >This would mean you do not have to lift the oxidizer for the 1st stage...   
      
   Why is that an advantage?  Liquid oxygen is compact, relatively easy to   
   store and handle, and so inexpensive that it's nearly free.  It *is*   
   heavy... but with rockets, extra thrust is cheap.   
      
   Design group after design group has come up with an elegant jet/rocket   
   design, and as an afterthought compared it to an all-rocket approach...   
   and been startled to discover that the all-rocket system looked to be   
   simpler, more capable, and cheaper both to develop and to operate.   
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