Didn’t they look at all kinds of ideas earlier like squirting some propellant or water out over the skin on the way down, and wasn’t steel chosen for its thermal robustness? Did they get into the problem and realize it’s a lot harder and abandon those things for tiles?
Maybe they will have to sacrifice more payload mass for active or passive shielding or more fuel for powered deceleration. That would yield a less impressive lifter but with full reusability.
Interestingly, the inside surface of a rocket nozzle is covered with tiny holes. Fuel is circulated in a jacket around the nozzle both to pre-heat the fuel and to cool the nozzle. Additional cooling of the nozzle comes from fuel leaking into the combustion chamber through those holes, carrying away the heat so it doesn't melt the nozzle. It's called boundary layer cooling.
It was one of the technological breakthroughs of von Braun's team with the V2.
They already plan refueling infrastructure in orbit. That would include stuff to "squirt" on the way down if necessary. If they can use one extra launch to reuse 5-10 starships that might be interesting. Noone knows yet if it's actually needed.
Yeah for rapid reusability tiles aren’t going to work, too fragile. Iirc it was with a lot of reluctance they went with tiles and will have to make breakthroughs on the heat shielding to get where they want to be.
Maybe they will have to sacrifice more payload mass for active or passive shielding or more fuel for powered deceleration. That would yield a less impressive lifter but with full reusability.