From: joe@strout.net   
      
   In article <50gZc.10673$5w4.2149@fe22.usenetserver.com>,   
    richie086  wrote:   
      
   > would the use of balloons to lift some sort of delivery vehicle or   
   > rocket into the very upper atmosphere work?  has this ever been attempted?   
      
   Yes, and yes, though never for an orbital vehicle, and it doesn't bring   
   as much benefit as you probably think it does.  The chief benefit is   
   that the rocket can be optimized for near-vacuum conditions, which makes   
   it more efficient than if it has to work both in the atmosphere and in   
   vacuum.  (Of course staging achieves the same thing.)   
      
   > Isn't half the cost of putting the space shuttle up   
   > or any rocket into orbit due to how much the fuel costs?   
      
   No, fuel is pretty cheap.  But it's true that accelerating all that fuel   
   requires more fuel, in a nasty feedback loop that leaves you very little   
   mass allowance for payload.  Launching from altitute helps a bit, as   
   noted above.  But to reach orbit, you still need to accelerate your   
   rocket to orbital velocity (about Mach 27).   
      
   Best,   
   - Joe   
      
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