XPost: sci.space.policy, sci.physics, sci.astro   
   From: fjmccall@gmail.com   
      
   Lofty Goat  wrote on Sun, 03 Jun 2018 11:05:53   
   -0500:   
      
   >On Sun, 3 Jun 2018 03:58:11 -0400, "Robert Clark" wrote:   
   >   
   >> ... a functional aerospike engine ... vaporware....   
   >   
   >Perhaps someone can clear something up for me:   
   >   
   >In a conventional rocket engine with bell-type nozzles the pressure of   
   >expanding gas against the inside of the nozzle propels the rocket.   
   >   
      
   Incorrect.   
      
   >   
   >The greater the area of said nozzle, the more energy is recovered from   
   >the expanding gas which explodes within, up to a point.   
   >   
      
   Incorrect.   
      
   >   
   >In an aerospike rocket engine, what does the pressure of the expanding   
   >gas act against to propel the rocket?   
   >   
      
   Newton's Law:  For every action there is an equal and opposite   
   reaction.  Throw gas out back, rocket goes forward.  No requirement to   
   'push against' anything.   
      
   >   
   >BTW, I've read all sorts of very imaginative explanations of aerospikes,   
   >yet none has shown a believable diagram of the forces at work.   
   >   
      
   The same as any other rocket.  Mass thrown after equals motion   
   forward.  All the bell does is try to make more of the gas go directly   
   'aft' as it exits.   
      
      
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   "Some people get lost in thought because it's such unfamiliar   
    territory."   
                                         --G. Behn   
      
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