On Friday, August 23, 2019 at 10:52:58 AM UTC-5, trident wrote:   
   > Recently I learned that solid Nuclear thermal rockets need not run on   
   hydrogen with its meek density. They can run on Water or ammonia. Using water   
   as a propellant slashes expected specific impulse by half, from 8 to 4 km/s.   
   But stilll this rocket has    
   greater Isp than most chemical rockets with exception of LOx/Lh2 systems,   
   which also  suffer from being robust, like hydrogen NTR.   
   >    
   > My questions is: Why nobody (to my knowledge at least) never explored the   
   possibility of water NTR. I know that DUMBO NTR in rocket's first stage may   
   give you creeps, but the air-beathing NTR with nuclear firs stage was at least   
   theoretically    
   investigated whereas water NTR was not? Why is that?   
      
   It _has_ been explored as a theoretical concept.  So have several others.   
      
   As you note, what stops any of the various theoretical proposals from getting   
   off the drawing board is the perception (which was certainly true in the past,   
   but might be changing gradually now) that the public and more cautious parts   
   of the government    
   would simply never permit such a thing.  Thus it remained mostly a matter of   
   theoretical modeling and speculation.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)