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by strainer 2458 days ago
From the sounds of it steel structure can basically handle much greater temperatures routinely and also even more in rare situations that might mean retiring the ship afterward but not losing everything. In his presentation Elon says that aluminum alloy or carbon fiber structure is basically done for at 300 to 400 Celsius, well that's the temperature at which stainless steel can just begin to get conditioned by heat, it doesn't structurally 'melt' until over 1000 Celsius.

Although its a curious topic, I would have no doubt that whatever temperature cycling they design parts of the structure to go through in their "rapidly reusable" regime, the effects of "heat fatigue" or whatever to call it will have been rigorously assessed .

2 comments

What do you mean by Handle?

Steel won't melt at 300-400 Celsius but "handling" those temperatures for 10 minutes will change the properties of the material, possibly by a lot, so you don't need "melting" for structural collapse (Twin Towers style).

As the GP says, if you put cold rolled steel, which has an elastic yield strength of >1500 MPa, at 300-400 Celsius, then it is only a matter of time (30-120 min) till the elastic yield strength sinks to 500 MPa or less.

So either this is a single use device, or the steel isn't reaching temperatures over 250 Celsius, or the steel isn't cold rolled but is a low strength steel instead (although that would have other problems).

Re-entry will take something on the order of 10m or less. Even the space shuttle only took 30 minutes while flying like a plane. There will be no circumstances where the ship is going to be subjected to that amount of heat for 30-120 minutes.

> or the steel isn't reaching temperatures over 250 Celsius

That might be the case. The space shuttle had an aluminum structure that would fail at 175C, and now we have 40 years of technology advancements for the heat shield.

Also I notice Cr-Steel's elastic yield strength at 400C is about 87% of its strength at room temp and I don't think it does alter significantly over these timescales at that temperature. It will be interesting to see how high it can be routinely cycled without losing its temper, but it seems to certainly provide much more overhead for safety margins as well as routine operation.

[1] https://www.engineeringtoolbox.com/young-modulus-d_773.html

it doesn't structurally 'melt' until over 1000 Celsius

Is this why jet fuel can't mel..... ah never mind.

I thought I felt deja vu :)