🔍 Feature Column｜What Steel Powers SpaceX's Starship?

✍️ By DONG-YU STAINLESS STEEL ENTERPRISE CO., LTD.

Introduction｜Steel is Flying Again

While most aerospace manufacturers have pursued lighter, costlier, and more complex materials like carbon fiber and advanced aluminum alloys, SpaceX took a radically different path. In 2019, Elon Musk announced that the company’s Starship rocket would be built using stainless steel, a material many considered outdated for spaceflight.

But this choice was not driven by nostalgia. It was a calculated move rooted in performance, cost, durability, and reusability.

Today, let's explore why stainless steel, especially specific alloys like 301, 304L, and SpaceX's proprietary 30X series, has become the material of choice for one of the world’s most ambitious aerospace programs.

1. High-Temperature Resilience: Surviving Atmospheric Reentry

When a rocket reenters Earth's atmosphere, it faces skin temperatures exceeding 1,400°C (2,550°F). Most carbon composites degrade at around 300–500°C, and aluminum alloys begin to weaken near 660°C.

By contrast, stainless steel offers:

1.      Melting points above 1,400°C, enabling structural integrity during reentry

2.      Excellent thermal fatigue resistance

3.      A surface that can directly face heat without heavy ablative shielding

This allows Starship to reduce the need for complex heat-shield tiles, minimizing part count, maintenance complexity, and failure points.

2. Cryogenic Toughness: Built for Liquid Oxygen and Methane

SpaceX rockets use liquid methane (−161°C) and liquid oxygen (−183°C) as fuel. These ultra-cold temperatures cause many materials to become brittle.

Initial prototypes used 301 stainless steel, known for high strength. However, field testing revealed weaknesses under cryogenic cycling.

SpaceX then transitioned to 304L stainless steel, a low-carbon variant with:

1.      Better weldability

2.      Superior ductility at cryogenic temperatures

3.      Improved fracture toughness

Eventually, SpaceX developed its own custom alloy, 30X stainless steel, likely a proprietary evolution of the 300-series family optimized for both thermal resilience and manufacturability.

3. Cost and Production Efficiency: The Real Disruptor

Carbon fiber may offer a high strength-to-weight ratio, but its cost and complexity are barriers to scalability.

Material Type Approx. Cost per kg Fabrication Process Repairability Carbon Composite ~$135 USD/kg Molding, curing, autoclaving Poor Stainless Steel (304L/30X) ~$3–5 USD/kg Rolling, welding, forming Excellent

Stainless steel is not only 20x cheaper, but also:

1.      Easy to weld and shape using conventional methods

2.      Durable in both ground handling and repeated launches

3.      Ideal for rapid prototyping and quick iteration

These properties align with SpaceX's culture of "test, explode, iterate", enabling faster development and lower capital risk.

4. Design Philosophy: Simplicity Drives Speed

Elon Musk once said: "The best part is no part." This philosophy permeates Starship's stainless design:

1.      Steel allows for monolithic tank structures

2.      Crashed or damaged sections can be cut, re-welded, and flown again

3.      Transpiration cooling (where fuel seeps through steel pores) replaces complex tile-based thermal protection

Here, material isn't just a tool, it's central to the architecture of how SpaceX designs, builds, and scales.

5. Summary Table｜The Evolution of SpaceX's Stainless Steel

Generation Alloy Used Strengths Use Case Stage Gen 1 301 Stainless High strength, early prototypes Starhopper, SN1–SN3 Gen 2 304L Stainless Cryogenic toughness, weldable SN4–SN6 and beyond Gen 3 30X Custom Thermal + manufacturing optimized Starship production series

Final Thought｜The New Era of Stainless Steel

SpaceX's selection of stainless steel wasn't a compromise, it was a rethinking of what's truly essential for reusability, scale, and sustainability in spaceflight.

At DONG-YU STAINLESS STEEL ENTERPRISE CO., LTD., we see this as a signal to all industries: The future of steel isn't just grounded, it's launching.

From industrial tanks to orbital flight systems, stainless steel is proving its strength not just in properties, but in purpose.

📌 Follow us for more deep dives into material science and the evolving role of stainless steel across aerospace, medical, and advanced manufacturing industries.