Stainless

Why Use Stainless

When SpaceX CEO Elon Musk, announced their vision for the Super Heavy and Starship, initial designs made use of carbon fiber composites. However, one of the major revisions announced as the design evolved was a switch to stainless steel. 

Reasons:

• Cheaper Material
• Easier to fabricate
• Toughness to fracturing
• Becomes stronger at cryogenic temperatures (similar in strength to carbon composites)
• Has better heat and cryo resistance properties, allowing lighter designs
• Polished surface reflects radiative heating away

Reasons for Polishing

Stainless steel is prone to tarnishing and water marks, so polishing is important to restore its shine and stainless properties

A smooth surface is less likely to accumulate deposits which generally become focal points for localized corrosion.
A correctly polished stainless steel surface has a better resistance to corrosion than a surface that is roughly or badly polished.
All stainless steel finishes perform better when maintained and cleaned correctly. This is particularly important for use in aggressive environments, such as in the offshore or nuclear industries.

Buffing surfaces of the rings may be done with a compound that helps remove residual carbon from the pores at the steels surface to reduce oxidization.

Grades

• 301 is being used for the SN1 Rings
• 304L is being used for the nose cone.