From: nuny@bid.nes   
      
   On Saturday, August 13, 2016 at 10:44:25 PM UTC-7, A Random Person wrote:   
   > If Jupiter's atmosphere is 90% H2, then would it make sense to use a   
   > turbojet/ramjet/scramjet with Oxygen (or some other oxidiser) as fuel? How   
   > would its efficiency compare with that of conventional airbreathing engines?   
      
     Fun idea!   
      
     Hydrogen-fueled jet aircraft have been proposed for use in our atmosphere,   
   and AIUI the efficiency is about equal, given the different tankage   
   requirements and having to keep the hydrogen cold enough to make it dense   
   enough to get energy density    
   equivalent to conventional jet fuels.   
      
     A Jupiter-air-breathing jet would need liquid oxygen tanks, and would need   
   to move fast enough to gather hydrogen rapidly enough to stay aloft, meaning   
   altitude limits. Of course once the O2 runs out it's a glider and there's   
   nowhere to land.   
      
     Fluorine is a better oxidizer so you'd get more runtime than with oxygen,   
   but the "exhaust" is hydrogen fluoride, and if there's anything alive in   
   Jupiter's atmosphere it won't like that, not to mention the technical   
   challenges of keeping the engine    
   from dissolving- HF is VERY chemically reactive.   
      
     So, how about a Jupiter-air-breathing engine of some sort powering the   
   instrument package on a Jupiter balloon probe? It'd be cheaper than a nuke   
   generator and could be restartable so it wouldn't have to run constantly.   
      
     Another challenge; at the depth in Jupiter's atmosphere where the air   
   pressure is equivalent to Earth's at sea level, the temperature is ~ -100C and   
   you're in the ammonium-hydrosulfide clouds. When you go deep enough for what   
   we think of as shirtsleeve    
   temperatures you're back in mostly hydrogen but the pressure is ~ 5-10 Earth   
   atmospheres. So, whatever engine you choose, it won't work quite the same way   
   it would on Earth.   
      
      
     Mark L. Fergerson   
      
   --- SoupGate-Win32 v1.05   
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