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Comment by hwillis | Hacker News Reader

Definitely not hotdog (assuming that's from stem to stern). Musk wasn't totally clear when describing it, but he said mk3 would be in three months. The circumference of starship is 28.26 meters. For a single weld the entire length of the ship, the roll itself would need to be that wide.

The largest rolling mills in the world are ~4 meters wide[1]. They require backup rollers[2], ie rollers that push down the rollers that push down the rollers that push down the metal. Bending deflection increases with width^2. A 28 meter wide rolling mill does not exist AFAIK and cannot be built in three months.

[1]: https://www.aleris.com/company/rolled-products/

[2]: http://www.yourarticlelibrary.com/metallurgy/types-of-rollin...

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Wow what an incredibly substantive comment. I remember pretty clearly he said that there would be a single seam weld. Maybe I’m remembering wrong. Or maybe they’ll seam weld multiple rolls into a really wide roll and the only weld required to turn the final roll into the shell is that final hotdog weld.

I think the idea's to go like a Pringles can, with a spiraling single seam.

this is the correct answer. They can simply use the 4 meter wide steel no problem.

If getting out of your yoga pants is like opening a can of biscuits, then making a starship is like putting your yoga pants back on...

They can't do that because they need to thickness to taper off up the sides of the vehicle.

maybe, but that's also pretty unlikely. For reference here's where musk talks about it: https://youtu.be/sOpMrVnjYeY?t=3156

No real indication he means a spiral.

There are a lot of problems with a spiral. Thin sheets of steel, even hot rolled, are very affected by the rolling process. There's also the weld line going up in a spiral. That will cause uneven heat diffusion and expansion, which is a recipe for disaster given that the skin will be cold enough to liquify helium on one side and boiling hot on the other. Then red hot during reentry. Straight lines don't have the same problems.

I think when Elon said "there will be a single seam weld" (which I also remember), he meant this in comparison to the current welds.

It's been 12 hours and I only skimmed the video, so I might be misremembering what he said. My understanding was this: Mk1 is welded from plates so at each layer of the stack you have n-1 welds holding the n plates together. My understanding of his comment was that the steel coils will wrap around the major axis of the rocket but instead of each layer containing n-1 welds to join n plates, there will just be one weld in each layer to join the beginning and end of that coil. That would still leave you with welds joining the different layers of coils but only one "seam" weld along the rocket's major axis.

I feel like he was talking about a single weld on each ring section.

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