I thought that while the spare tiles did exist, there was never an actual safe procedure for replacing tiles (that didn't require being docked to the ISS) they were only carried to be available when the choice was between losing the entire crew on reentry or risking a crew member?

I don't quite understand how the airplane shape made it easier to model the loading and positioning? (Not saying you're wrong, just doesn't fit my intuition and I'm curious).

My understanding is that Shuttle didn't have to answer the questions about tile gaps etc because it used glue rather than mechanical attachments, if that's what you mean by positioning.

> I don't quite understand how the airplane shape made it easier to model the loading and positioning? (Not saying you're wrong, just doesn't fit my intuition and I'm curious).

You can approximate space shuttle reentry to roughly a 2d surface entering atmosphere. Because of airplane shape, the tile side faces atmosphere and the plasma goes around plane edges. Where as starship being cylinder doesn't have any separation boundary and plasma roughly goes more than 180% of the cylinder.

Having seen the shuttle in person in LA museum, I was struck by how much it looked like a plane sitting on a flat heat shield surface