I don’t doubt the physics of getting people there. Or at least objects with comparable mass to people.
I doubt he has anything resembling a workable plan for keeping large numbers of people alive for long periods of time on Mars.
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Relevant: https://www.acityonmars.com/ looks into a lot of the engineering, biological, economic, social, political and legal issues involved in actually trying to build a settlement with actual people on another planet. And the recurring theme, over and over as they talked to experts in each field, was that the research is either too early or too sparse to be usable yet (or in some cases, just not being done).
(My review of the book: https://hyperborea.org/reviews/books/city-on-mars/ )
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