Raptor engine fuel lines. The most obvious candidate is diamond nano threads. If they plan on using for cabling for a Space elevator. Then they should be suitable as a flexible fuel line outer layer. Having looked into the future(pressurised fuel lines at present stainless steel), I am sure that Space Ex Starship should have a successful launch. As the previous launch should have been successful, checking every component, like a Halo Elite Spacecraft 'load master', checking individuals equipment before deploying into space on a space flight. Is the right way to go. So getting it right takes time, regardless of the media circus!