From: jeff.findley@ugs.nojunk.com   
      
   "Andrew Nowicki"  wrote in message   
   news:44BCF84B.7338935F@nospam.com...   
   > Joe Strout wrote:   
   >   
   >> But airships (whether filled with hydrogen or helium) are.   
   >> Big ones can have a quite impressive lift capacity, too.   
   >   
   > The problem is how to bring the balloon or the airship   
   > back to the earth -- you would have to release lots of   
   > expensive hydrogen. The cost of making hydrogen is about   
   > 0.7 $/kg, but the cost of liquefying and transporting hydrogen   
   > from the oil refinery to the user raises the cost to about   
   > 3 $/kg. Hydrogen, like chlorine, is a destroyer of the ozone   
   > layer. If the rocket weighs 10 tons, you would spend about   
   > $50,000 on the hydrogen alone. Helium is even more expensive.   
      
   I'd think it would be cheaper to buy kerosene and build a conventional   
   LOX/kerosene first stage than it would be to build and operate an airship   
   big enough to replace said first stage.  The airship, after all, is going to   
   be so huge, it would need some big engines of its own just to maneuver back   
   to base once it's launch vehicle has been released.   
      
   Jeff   
   --   
       "They that can give up essential liberty to obtain a   
        little temporary safety deserve neither liberty nor   
        safety"   
   - B. Franklin, Bartlett's Familiar Quotations (1919)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)