SpaceX Stainless Steel Rocket Will Be Lighter, Stronger and Have 65X Lower Cost Material

Elon Musk explained to Popular Mechanics why SpaceX switched to a 300 series alloy of stainless steel.

Advanced carbon-fiber structure made very slow progress and the cost per kilogram was $135.

There is a lot of cutting and they would lose 35 percent of the material in processing. It has to have a lot of glue (aka high strength resin). They need 60 to 120 layers, which are called plies.

The carbon fiber is $200 per kilogram while the steel is $3 per kilogram.

Stainless steel that has a high chrome-nickel content does not become brittle at cold temperatures.

Stainless steel was used in the early Atlas rocket days. The early Atlas was a steel balloon tank. The flaw Atlas program used material that was too thin. It would collapse under its own weight.

300 series steel has a high melting point. Typically with aluminum or carbon fiber, for a steady-state operating temperature, you are limited to about 300 degrees Fahrenheit.

Steel can actually go to 1500, 1600 degrees Fahrenheit.

Kimi Talvitie rendered the SpaceX Super Heavy Starship with shiny metallic steel.

Kimi is now selling shirts and other products with his renderings of SpaceX vehicles.

Steel Rocket Design

The back of a rocket on re-entry does not need any heat shielding.

The forward re-entry-side has the first-ever regenerative heat shield. SpaceX has a double-walled stainless shell—like a stainless-steel sandwich with two layers.

Two layers are joined with stringers. You flow either fuel or water in between the sandwich layer, and then you have micro-perforations on the outside—very tiny perforations—and you essentially bleed water, or you could bleed fuel, through the micro-perforations on the outside. You wouldn’t see them unless you got up close. Transpiration cooling to cool the windward side of the rocket. So the whole thing will still look fully chrome, like a cocktail shaker.

Dyna-Soar Had Water Wall Cooling

The internal compartments of the Dyna-Soar were encased in ‘water walls’ which provided passive cooling. These reduced the 980 deg C re-entry equilibrium temperature of the airframe truss structure to 90 deg C and allowed the pressure shells of the compartments to be of conventional aluminum.

Dyna-soar was a manned spaceplane. It was canceled in 1963. The X-20A Dynasoar (Dynamic Soarer) was a single-pilot manned reusable spaceplane.

It as a hot temperature structure using a nickel super alloy.


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