From: no-spam@thank-you.com   
      
   Allen Meece wrote:   
   > < not necessarily pressure fed - that flies straight up, releases the   
   > second stage, and flies straight down to land at the launch site.>>   
   >   Something like >80% of the system's total fuel is spent to obtain the   
   > horizontal component of orbital flight.   
   >    Thus, the booster would get a few hundred miles down-range and would need   
   > wings to get back and that's what's called a flyback booster, something   
   > everybody knows will be required for CATS but designing it needlessly   
   > intimidates everyone at the same time.   
      
   Not me.  As soon as I make my third billion... :_>   
      
   It probably improves system reliability (and thus reduce overall cost)   
   to use parallel staging.  You don't launch until you see all engines on   
   both stages running.  It also provides a survivable abort for the   
   orbiter in many (not all) cases of something awful happening to the   
   booster.  Of course the beauty of true complete reusability is that it   
   allows you to wring all of the errors both out of the design of the   
   vehicles and of their manufacturing processes, and so the probablities   
   of "something awful" happening go way down.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)