From: gcowan@eagle.ca   
      
   Cruithne3753 wrote:   
   >   
   > psturroc@gmail.com wrote:   
   > > Are there any rocket fuels -- existing or potential -- that are less   
   > > polluting than kerosene or hydrogen?  If so, are any of them   
   > > economically feasible?   
   > >   
   > Hydrogen + oxygen = water vapour.  Can't get any less polluting than that.   
      
   Actually water doesn't naturally tend to rise high in the stratosphere,   
   so its release there by rockets or aircraft can be considered pollution,   
   although not, in my opinion, of a very serious kind.   
   I believe it freezes and fairly soon falls out.   
      
   A rocket with liquid air for propellant,   
   powered by a laser on the ground,   
   would be a little cleaner than an oxyhydrogen rocket.   
   Isp probably would be much inferior,   
   although in principle one could put a lot of laser   
   power into heating a low mass flow rate of air   
   from the rocket's tanks, and get a crazy chamber temperature   
   in the middle of the chamber but not at the walls.   
      
      
   --- Graham Cowan, former hydrogen fan   
   Boron fire good. http://tinyurl.com/4xt8g   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)