As SpaceX continues to fine-tune its Starship, the sixth test flight of its two-stage mega-rocket took place in November 2024, and nickel was onboard. Nickel was pivotal in providing optimal strength and resilience while offering economies of scale.
By Kim Oakes, Nickel Institute
The test flights serve as a platform for learning and advancing the successful elements of the program. The fourth launch marked a significant milestone as it was the largest and most powerful rocket ever flown.
The Starship has two stages: the Super Heavy booster and the Starship spacecraft. Their main structure is made from 300 series nickel-containing stainless steel. Earlier prototypes were constructed of 304L (UNS S30403), which still may be the case, though SpaceX has hinted that a 300 series variant with optimised properties may be the final material.
Both stages are equipped with Raptor engines, which utilise nickel-base alloy 718 (N07718) in the combustion chamber due to its exceptional strength and heat resistance.
Originally, the plan was to construct the rocket using carbon fibre, chosen for its high-tensile strength and low density. However, in December 2018, the structural material was switched to 300 series stainless steel. Elon Musk cited several reasons for this change, including lower cost, ease of manufacture, increased strength of stainless steel at cryogenic temperatures, and its ability to withstand high heat.
According to Musk, carbon fibre is incredibly pricey, costing some $135/kg (or 2.2 lbs), with as much as 35% of the material wasted just through the cutting and shaping process. Stainless steel costs less than $3/kg with very little waste.
Stainless steel also benefits from a high melting point, enabling it to resist the high temperatures encountered during re-entry and reducing the need for heat protection insulation.
In addition, the fabrication is much easier and faster. It is manufactured by stacking and welding stainless steel cylinders, which is no more difficult than the welding used to construct stainless steel tanks, which is routinely done. Since the rocket is intended to be reusable, repairs are possible and easy to perform.
Overall, nickel-containing stainless steel is helping Starship achieve its primary objectives: controlling launch costs, enabling the reuse of both rocket stages, increasing payload mass to orbit, facilitating launch frequency, and creating a mass-manufacturing pipeline, all of which can be adapted to a wide range of space missions.
Considered a success, the latest launch advances SpaceX’s lofty mission to establish human settlements on the moon and Mars.
NASA is counting on Starship’s success to return humans to the moon. The most recent crewed lunar mission was Apollo 17 in 1972. SpaceX’s objective is not only to return humans to the moon but also to go beyond and reach Mars.
About Nickel Institute
The Nickel Institute is the global association of leading primary nickel producers. Its mission is to advocate for the responsible supply and sustainable development of nickel and the nickel industry. For information, please visit nickelinstitute.org
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