From: mooregr@deletethisgreenms.com   
      
   "Snidely"  wrote in message news:mn.3d6c7e4b28a58571.127094@snitoo...   
   >   
   >With a quizzical look, JF Mezei observed:   
      
   >> What is so different with Falcon9 that allows it to ingnite its own   
   >> engines that nobody else can do?   
   >   
   >Designed for restarts from the beginning.  Most second stage engines are   
   >also so designed, plus the shuttle main engines.  I don't know if SLS has   
   >retained that capability, but Wikipedia suggests that the RS-25 has it   
   >still ... dual-redundant spark igniters in the injectors of the preburners.   
      
   The SSME were not designed to have relight capability. I don't know the   
   details, but a pad abort for example required them to do servicing.   
   Since there was no real reason for inflight reignition ability, my   
   understanding is they never put it in.   
      
   --   
   Greg D. Moore                   http://greenmountainsoftware.wordpress.com/   
   CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net   
   IT Disaster Response -   
   https://www.amazon.com/Disaster-Response-Lessons-Learned-Field/dp/1484221834/   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)