Reference the heat loads of reentry - SpaceX has found a much simpler, and cheaper, option.....
If you’ve reduced the fuel load, and size of the fuselage, by up to 80%, you can afford the extra weight of the steel - if there is any, because it eliminates the need for the eight of tiles etc.
https://www.space.com/43101-elon-mus...-starship.html
https://arstechnica.com/features/201...little-closer/