Several comments asking me about Stoke Space What they are doing (regeneratively-cooled metallic heat shield using LH2) is pretty neat and has promise. I talk sometimes about how what SpaceX did with Falcon 9 was more of an "engineering problem" (taking proven mid-TRL technology and making it work on a real system) than the issues with Starship's heat shield that I see as more of a "physics problem" (depending on your definition of "rapid" reuse). Engineering problems can be solved with iterative design and brute force. Physics problems need true advances in science and technology. All that to say, IMO what Stoke is trying to solve is an engineering problem. With the right people, enough money, and enough time, I think it will work. Anytime your design relies this heavily on hydrogen you're inviting some (incredibly small) demons to the party, but alas, not my problem. I'd love more details on their ground testing at "higher heat loads" than what is experienced in flight. But last I heard they're targeting a launch test late this year? Looking forward to finding out...