From: nospam@127.0.0.1   
      
   David Spain  writes:   
      
   > JF Mezei  writes:   
   >   
   >> On 2020-11-08 23:32, Greg (Strider) Moore wrote:   
   >>   
   >>> 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.   
   >>   
   >>   
   >> In a previous message, it was alluded that some nasty chemicals used to   
   >> ignite engiunes (I assume hydrazyne, right?). Isn't it just a question   
   >> to grow the tank and have the pump disperse finite amount such that theu   
   >> can ignite 3 or 4 times during a flight?   
   >>   
      
   If you are interested in re-igniting a LH2/LOX engine go do a web search   
   on the Saturn V third stage. It had to light both for Earth orbital   
   injection as well as for Trans Lunar Injection.   
      
   https://en.wikipedia.org/wiki/Rocketdyne_J-2   
      
   The above answers the question: to wit: spark plugs, ullage and pre-chill.   
      
   Dave   
      
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