From: Peter.Card@jet.uk   
      
   Mike Lorrey wrote:   
      
   > NASA's fixation on LH2 has more to do with political correctness and a   
   > need to get their budgets approved by congressmonsters who are beholden   
   > to tree huggers more than to engineers. While it is a great fuel for   
   > propulsion in a vacuum, its penalties when travelling in the atmosphere   
   > preclude it as a serious fuel for any aircraft, hypersonic jet, or SSTO   
   > reusable launch vehicle.   
      
   ?? I am not so sure about that last bit. There are trade-offs between   
   the superior specific impulse of an LH2/LOX rocket, which buys you are   
   larger mass-fraction, and the heavier structure required by the large   
   cryogenic LH2 tanks. The drag is less of an issue for an SSTO I would   
   think. A typical trajectory starts off vertical and rapidly leaves the   
   dense lower stmosphere, so the delta-vee budget of an SSTO would be   
   dominated by the requirement to reach orbital velocity.   
      
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