Elon Musk has been teasing his Twitter followers since late 2018 with previews of the SpaceX Starship prototype, a reusable rocket he has dubbed the “Stainless Steel Starship” – prompting some followers to ask why he has chosen steel over carbon fibre in the construction of the upcoming space vehicle.

The Starship is a multi-purpose spacecraft designed to allow humans to travel into space, as well as to deploy new satellites and space telescopes from its large forward cargo bay, before returning safely to Earth ready for its next mission.

But it is Musk’s decision to use stainless steel to build the ship that has raised some eyebrows among followers and space engineering enthusiasts, including some who questioned the extra weight of the Starship compared with if it were to be built out of carbon fibre.

Why use steel for SpaceX?

Musk explained that there are numerous benefits to using stainless steel instead of carbon fibre:

  • The usable strength of stainless steel is slightly better than carbon fibre at very cold temperatures.
  • At room temperature stainless steel performs only slightly worse than carbon fibre.
  • At very high temperatures stainless steel performs “vastly better” than carbon fibre.

He added that the SpaceX Starship will have a “maximum reflectivity” mirrored stainless steel surface finish which will not be painted, as the skin will get too hot during missions for it to be painted.

Although the prototype version does not have windows or other surface features, Musk also explained that the final version used in manned missions will be given windows – which may potentially be coated with gold for reflectivity.

The iconic steel design

The bulbous shape of the Starship has been compared to the comic book designs of the mid-20th century, when artists imagined rockets made of polished metal with the iconic ‘rocket ship’ shape including a domed nose and tail fins.

As of February 2019, development had reached the engine testing phase, with Musk posting images of the Starship Raptor engine on its testing stand at SpaceX Texas.

The Starship prototype will use a 200 metric ton booster throughout its journey, whereas the final production model will have two different boosters, one optimised for sea-level thrust of around 250 tons, and one optimised for use in the vacuum of space.

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