Elon Musk

It's very resilient.

You can modify it easily.

If you want to attach something, you just weld it right on.

So very easy to work with, very low cost.

And...

Now, like I said, at cryogenic temperature, similar strength to weight to carbon fiber.

Then when you factor in that, we have a much reduced heat shield mass because the melting point of steel is much greater than the melting point of aluminum.

It's about twice the melting point of aluminum.

So you can just run the rocket much hotter?

Yes, especially for the ship, which is coming in like a blazing meteor.

You can greatly reduce the mass of the heat shield.

So you can cut the mass of the windward part of the heat shield maybe in half.

And you don't need any heat shielding on the leeward side.

So...

The net result is actually the steel rocket weighs less than the carbon fiber rocket, because the resin in the carbon fiber rocket starts to melt.

Basically, the carbon fiber and aluminum have about the same operating temperature capabilities, whereas steel can operate at twice temperature.

I mean, these are very rough approximations.

People will... I won't build a rocket paper.

What happens is people will say, oh, he said this twice.

It's actually 0.8.