He's been key in all kinds of work including: Phase Reluctance Electric motors in Teslas, Octovalve and superpump integrated heating/cooling design, Raptor Space-X methane dual-regenerative rocket engines, use of stainless-alloy metal skins instead of carbon-composite for Starship re-entry heat sheild... and yes before you rant, there were of course other smart people involved on the projects.
I won’t rant, but I have also been key in all kinds of engineering work…. Key meaning asking questions “can we do this” “why not” “ok get it done”