SpaceX has created its own Starship alloys and no longer uses 301 stainless, Elon Musk said on August 23, adding detail to a materials path that already left carbon fiber for stainless steel years ago.
“This is why I switched Starship to stainless steel. We have since created our own new alloys and no longer use 301,” Musk wrote on X. He did not name the proprietary alloys or publish a public metallurgy sheet.
The reply is a short update on a long-running materials story. SpaceX abandoned carbon-fiber Starship tanks years ago for stainless structures that better handle cryogenic propellant and reentry heat. Musk’s August 23 comment adds that the original 301 grade is no longer the recipe SpaceX flies today. It is a materials milestone stated in one line, not a full materials white paper.
Hardware progress is moving in parallel. The ship assigned to Flight 14 completed a full-duration, 60-second static fire with all six Raptors on August 21, the official dress rehearsal before stack and fly. Musk has also said SpaceX should wind down Falcon once Starship flies several times a week, so scarce engineering and production talent can push toward a higher Starship cadence.
Custom alloys fit that same focus: fewer borrowed grades, more in-house metal tuned for tanks, heat, and reuse. Beyond Musk’s quote, SpaceX has not detailed hardness, weld behavior, or heat-shield interfaces for the new mixes. For now, the only firm claim on the record is stainless plus proprietary alloys — and no more 301.
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