From: nospam@127.0.0.1   
      
   On 2020-07-12 8:22 PM, JF Mezei wrote:   
   > Was there any confirmation of the cause of the SN4 instant explosion?   
   > (I assume internally they know).   
   >   
   >   
      
   Last I read it was due to problems with the methane line quick   
   disconnects in the test stand. They properly disconnected but failed   
   spectacularly during reconnect. Allowing methane to leak massively until   
   it diffused enough to catch fire and explode in a fuel/air explosion.   
   I'm assuming the source of the leak was the fuel tank of SN4 itself   
   since upstream supply valves should have been closed to prevent leaks   
   from the methane supply lines. But I do not know this to be fact. Since   
   the fire and explosion blew SN4 off the test stand and not the supply   
   lines or tanks, this is probably a safe assumption.The tweet from Elon   
   mentioned a problem with the disconnects but not the exact issue. I'm   
   not sure where I got the re-connect issue description from, might have   
   been from a web forum I read. But it would make some sense. I had   
   experience with hydraulic quick disconnects in my youth. Usually a   
   disconnect was not nearly as hard as a connect in my experience.   
      
   Dave   
      
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