From: damarkley@gmail.com   
      
   On Friday, June 26, 2020 at 8:09:00 AM UTC-4, David Spain wrote:   
   > On 2020-06-23 2:49 PM, JF Mezei wrote:   
   > > Also, since SN7 was built as a test tank without both tanks or the   
   > > engine mounting structures under it, I assume SpaceX are testing new   
   > > tank building materials/techniques?   
   > >    
   >    
   >  From what I have read elsewhere, yes this appears to have been a    
   > deliberate "test to failure". Apparently SpaceX is experimenting with a    
   > new steel alloy called "304L". Elon was said to have been pleased that    
   > it failed first as a leak before a rupture. They were testing with    
   > cryogenic liquid nitrogen as a prelude to other materials, presumably    
   > liquid oxygen and liquid methane.   
   >    
   > Dave   
   >    
   > > https://futurism.com/the-byte/spacex-blows-up-starship-tank   
   > > https://www.teslarati.com/spacex-starship-tank-blown-up-new-alloy/   
      
   304L is a slightly modified version of 304 steel.  The main difference is that   
   304L has less carbon, 0.03% as opposed to 0.08% in 304.  That means 304L has   
   slightly lower tensile strength and yield strength.  But that reduction in   
   carbon means it is    
   easier to weld and gives stronger joints.  Interestingly, most metals get   
   stronger as they get colder.  An exception is carbon steels as the carbon   
   inclusions provide weak points when the metal is cold.  So from that view,   
   304L is even better than 304.   
      
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