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Comment by themafia | Hacker News Reader

> every flight needed to have a perfect heat shield.

Which is a little easier to do when your craft is shaped like a plane and not a simple cylinder. The loading and positioning were easier to model and then achieve in flight.

The shuttle also flew with repair kits and glue that could be used in a vacuum. The astronauts could perform an EVA and work to replace damaged tiles and there were published plans on how to do so. NASA unfortunately figured out very late that using the Canadarm to image the bottom of the shuttle immediately on achieving orbit was extremely necessary given the icing problems of the external tank.

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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.

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

> 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.

Ah, that makes sense!

IR reflectivity of stainless must help a good deal for the unshielded parts. I wonder if the internal surface is painted or finished in a way to help radiate the heat away internally.

Is there any active cooling of any of the skin that we know of?

They've been testing some active cooling tiles (believed to be responsible for the orange residue on the heat shield after reentry in this latest test), but otherwise the only "active cooling" of the skin would be due to the cryogenic propellants being in contact with the inner side of the skin.

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