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Musk interviewed by Popular Mechanics. 

 

Subject: Starship & stainless steel.

 

https://www.popularmechanics.com/space/rockets/a25953663/elon-musk-spacex-bfr-stainless-steel/

 

Summary

 

Alloy: initially (Starship Mk 1?) 301 stainless steel, later something "special";

 

Why stainless?: strong at cryogenic temps, high heat bearing capacity;

 

Structure: double-walled on windward side during re-entry with transpirational active cooling; 

 

Transpirational active cooling: the outer wall has micro-perforations, through which liquid CH4 or water is sprayed to create a boundary layer. That's your heat shield. No heat shield needed on the leeward side because stainless can take those loads;

 

Counterintuitive?: transpirational + stainless ends up lighter than composites with a passive heat shield, and it's far cheaper.

Edited by DocM
  • Thanks 1

This design change is the core of what SpaceX stands for. Take off the shelf technology that was limited to certain applications and make it flight worthy.  The more details that get released the more it is pure ######## genius. There should be no questions as to SpaceX getting this to work. The F9 reusability has already proven to be a showstopper. Old space is banging their head against the wall on this.

  • Like 3
3 hours ago, flyingskippy said:

This design change is the core of what SpaceX stands for. Take off the shelf technology that was limited to certain applications and make it flight worthy.  

>

 

IIRC transpirational metal sheets are used in some deicing systems - millions of laser-cut holes per square meter for "sweating" glycol.  This puts the tech squarely in the COTS  territory you mentioned.

Edited by DocM

Yea, the weeping wing system changed the way small aircraft dealt with in flight icing. The alternative was pneumatic boots that cycled air though sealed channels. It didn't always work until the ice was thick enough to break off and robbed horsepower from the engine.

4 hours ago, anthdci said:

looks like more than a small delay, that looks totaled. 

It was just the fairing, not the whole vehicle.  Not attached to the propulsion module. 

 

Musk said fixed in a few weeks, and it'll take about that long to qualify the Raptor engines for it. 

 

More on the wind events,

 

 

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