.@elonmusk on why SpaceX builds Starship out of stainless steel instead of carbon fiber "Best design decision on this whole thing is a 301 stainless steel. ... Does that mean it's heavy? No, actually, it's the lightest construction." "You say, what is the strength at cryogenic temperature? Oh, much, much stronger. At very low temperature, almost twice as strong." "For a reusable ship, you're coming in like a meteor. You want something that does not melt at a low temperature. You want something that melts at a high temperature. And this is where steel is extremely good as well." Elon Musk at the SpaceX Starship Update, Sept 28, 2019 Seven years later, those steel Super Heavy boosters are getting caught by the tower, and Flight 15 is up next.