The manufacturing of rockets out of stainless steel also does not have much existing knowledge behind it. Nor does landing a rocket booster or first stage back on earth. Or staging a rocket this large and reusable.

What the engineers at SpaceX are pulling off on a regular basis is crazy. Having a reusable rocket system of this kind and size was unthinkable at many points in history. Just a shame their work gets overshadowed by a guy who takes all the credit while doing almost none of the work.