Here's an interview with Tom Mueller (design lead on the Merlin engine, and SpaceX's chief of propulsion from inception until he semi-retired a few years ago),

Here's an interview with Tom Mueller (design lead on the Merlin engine, and SpaceX's chief of propulsion from inception until he semi-retired a few years ago), talking about working with Elon. The most relevant anecdote is Elon demanding he find a way to get rid of some large and expensive valves -- which Mueller initially thought impractical, but he tried anyway at the boss's insistence, and wound up with a much cheaper, lighter, more reliable engine he was really pleased with. Elon didn't do all the detail work necessary to make that happen, and perhaps he couldn't (there's a reason he keeps paying everyone else), but it's odd to deny he has a role in the process. https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_interview_speech_skype_call_02_may/dhiyi3n/ https://www.reddit.com/r/spacex/comments/6b043z/tom_mueller_...