8 ms·

I totally understand why they've gone for that design but the welded together steel plates really make me think of the sort of thing Wallace and Gromit would bu

I totally understand why they've gone for that design but the welded together steel plates really make me think of the sort of thing Wallace and Gromit would build.

deleted 7y ago
[deleted]
faead_ 7y ago
he addressed in presentation, from what i remember it had a lot to do with cost. Like $130k/ton with carbon vs $3k/ton with steel. He mentioned a few other factors. Also it allowed them to build outside, not sure if t that is true in production.
- allannienhuis 7y ago
  the material isn't the question, it's why they had to weld it together in a patchwork quilt. Elon talked about the next version would simply have rolled coils with a single seam weld (although the cylinders would have to be welded together too), which would be better structurally and cosmetically, and likely lower cost of production. Sounds like they just didn't have the rolling machines to do the job, or perhaps there was an availability issue with the specific alloy.
  - _Microft 7y ago
    It will reduce the length of the welds (for the hull) quite a bit. The number of rings is roughly 35 for Starship, with about ten vertical seams each. For easier thinking, line the vertical seams up and you see that this gives 50m length per vertical seam from bottom to top of Starship. So there are a total of 500m for that. 35 rings with ~28m circumference add up to about 1km of seams between them. Now if they can use rolls twice as wide and only a single vertical weld each, then that's 500m between the rings and 50m for a single vertical seam. 550m of welds there instead of 1.5m before. This should speed things up quite a lot and reduce the cost of labour. Raptor production is the real bottleneck, though.
    - jcims 7y ago
      >Raptor production is the real bottleneck, though. They are shooting for one per day, no? Based on the differences identified in the three hanging under the Boca Chica vehicle now, it’s still in development.
      - JshWright 7y ago
        They just shipped he 12th one. Definitely still in the development/ramp up process.
      - de_watcher 7y ago
        He said that it's about one per week. One per day will be in several months.
    - x3n0ph3n3 7y ago
      The way I understood the presenation, they plan to use a single piece of steal, bent at an angle and rolled around (think one of those Pillsbury roll cans) with a single weld seem, in a giant helix.
  - bluthru 7y ago
    And then you can make it a spiral of steel to eliminate the vertical welds.
  - emilecantin 7y ago
    > although the cylinders would have to be welded together too No, they'll do a helical weld, exactly like large pipes (like this: http://www.xysteelpipe.com/upload/201512118145340710.jpg http://www.xysteelpipe.com/upload/201512118145340710.jpg) You basically need to do that as the steel rolls off the press, though, which is why they didn't do that for Mk I. They'll need to cold roll the steel onsite.
    - 4684455 7y ago
      They will not do a helical weld because the steel's thickness varies from the top to the bottom of the cylinder, according to Elon Musk. https://twitter.com/HarryStoltz1/status/1162595874561617920 https://twitter.com/HarryStoltz1/status/1162595874561617920 https://twitter.com/elonmusk/status/1162601447235604480?lang=en https://twitter.com/elonmusk/status/1162601447235604480?lang...
- baybal2 7y ago
  Imagine the autoclave the size of a rocket. Composite tanks on few rockets being flown with them are made in one of a kind, purpose built autoclaves
  - greglindahl 7y ago
    Out-of-autoclave methods are mature and common these days.
    - baybal2 7y ago
      Do they get you the same strength, fill ratio, and allow for usage with aerospace specialty epoxies?
- elihu 7y ago
  He also talked about how stainless steel has a high melting point (which means their re-entry heat shield doesn't need to be as thick) and gets stronger rather than weaker at very low temperatures.
- emilecantin 7y ago
  As he said in the presentation, it was because at cryogenic temperatures (which is the important part when you're building a liquid oxygen / methane tank) 301 stainless is actually _stronger_ than Al / carbon fiber. It also handles heat much better, which allows you to have a much thinner heatshield. Both characteristics combine to give a lighter rocket than one built out of Al / carbon fiber. The price is just the cherry on top.
HenryKissinger 7y ago
It reminds me of the F-104 Starfighter: https://upload.wikimedia.org/wikipedia/commons/d/de/Lockheed_XF-104_%28modified%29.jpg https://upload.wikimedia.org/wikipedia/commons/d/de/Lockheed... Or the F-86 Sabre: https://upload.wikimedia.org/wikipedia/commons/3/39/F86F_Sabres_-_Chino_Airshow_2014_%28cropped%29.jpg https://upload.wikimedia.org/wikipedia/commons/3/39/F86F_Sab...
- chr1 7y ago
  Is the surface of these less smooth than surface of normal rockets/planes, or is it simply the effect of mirror like surface making bumpiness easier to see?
  - skykooler 7y ago
    The latter - a matte surface would be lit from essentially the same angle, but even a tiny discrepancy causes big shifts in a reflection.
mattlondon 7y ago
I am totally with you on this - I just can't get over how utterly rudimentary and basic this thing looks! I can't wait to see it fly! I am so used to seeing space stuff done in clean rooms, and things taking years and years to come to fruition (e.g. hearing about and seeing NASA or ESA probes etc getting made) that to see what is essentially a bunch of guys in a field just welding something together blows my mind. I mean, is it just the outside that looks like that and inside it is ultra-exotic materials and tanks? Of course the engines are sophisticated machinery, but what about the insides? Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside?
- extrapickles 7y ago
  I suspect most of the structure that gets really hot or cold is steel. To save weight, they are probably also letting more of the rocket get colder/hotter than normal, thanks to the wider temperature range of steel. Once the temperatures get reasonable, it might be aluminum or or carbon fiber. The passenger/cargo/avionics section are probably the only areas where this would be true, so a bulk of the rocket will be steel.
  - hinkley 7y ago
    Steel can tolerate a lot more deflection before it bends, and much more stress before it cracks. And while I would never expect a space craft mechanic to employ this technique, any bike mechanic will happily offer to bend steel back into shape for you, but bent aluminum or carbon fiber is scrap. Bending it back will fracture it, if it hasn't already. When Canondale hit the big time, they had one model year where they made the dropouts out of solid aluminum and in the next model year the derailleur hanger was bolted on. It's the easiest part to bend and there's no repairing it. Bad enough for road bikes, spectacularly dumb for mountain bikes.
- balfirevic 7y ago
  > Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside? Nope, it's just steel. Outside shell is the tank.
Florin_Andrei 7y ago
> the welded together steel plates really make me think of the sort of thing Wallace and Gromit would build The most beautiful thing in the world is success.
deleted 7y ago
[deleted]
iamgopal 7y ago
We work with multiple tens of ton of SS steel per month, and I would have never thought this heavy thing could fly with all the stress of the sky. I hope it fly good.
de_watcher 7y ago
Scrapped together plates make you wonder how it won't fall apart on ascent or descent...

I totally understand why they've gone for that design but the welded together steel plates really make me think of the sort of thing Wallace and Gromit would build.

deleted 7y ago

[deleted]

faead_ 7y ago

he addressed in presentation, from what i remember it had a lot to do with cost. Like $130k/ton with carbon vs $3k/ton with steel. He mentioned a few other factors. Also it allowed them to build outside, not sure if t that is true in production.

allannienhuis 7y ago
the material isn't the question, it's why they had to weld it together in a patchwork quilt. Elon talked about the next version would simply have rolled coils with a single seam weld (although the cylinders would have to be welded together too), which would be better structurally and cosmetically, and likely lower cost of production. Sounds like they just didn't have the rolling machines to do the job, or perhaps there was an availability issue with the specific alloy.
- _Microft 7y ago
  It will reduce the length of the welds (for the hull) quite a bit. The number of rings is roughly 35 for Starship, with about ten vertical seams each. For easier thinking, line the vertical seams up and you see that this gives 50m length per vertical seam from bottom to top of Starship. So there are a total of 500m for that. 35 rings with ~28m circumference add up to about 1km of seams between them. Now if they can use rolls twice as wide and only a single vertical weld each, then that's 500m between the rings and 50m for a single vertical seam. 550m of welds there instead of 1.5m before. This should speed things up quite a lot and reduce the cost of labour. Raptor production is the real bottleneck, though.
  - jcims 7y ago
    >Raptor production is the real bottleneck, though. They are shooting for one per day, no? Based on the differences identified in the three hanging under the Boca Chica vehicle now, it’s still in development.
    - JshWright 7y ago
      They just shipped he 12th one. Definitely still in the development/ramp up process.
    - de_watcher 7y ago
      He said that it's about one per week. One per day will be in several months.
  - x3n0ph3n3 7y ago
    The way I understood the presenation, they plan to use a single piece of steal, bent at an angle and rolled around (think one of those Pillsbury roll cans) with a single weld seem, in a giant helix.
- bluthru 7y ago
  And then you can make it a spiral of steel to eliminate the vertical welds.
- emilecantin 7y ago
  > although the cylinders would have to be welded together too No, they'll do a helical weld, exactly like large pipes (like this: http://www.xysteelpipe.com/upload/201512118145340710.jpg http://www.xysteelpipe.com/upload/201512118145340710.jpg) You basically need to do that as the steel rolls off the press, though, which is why they didn't do that for Mk I. They'll need to cold roll the steel onsite.
  - 4684455 7y ago
    They will not do a helical weld because the steel's thickness varies from the top to the bottom of the cylinder, according to Elon Musk. https://twitter.com/HarryStoltz1/status/1162595874561617920 https://twitter.com/HarryStoltz1/status/1162595874561617920 https://twitter.com/elonmusk/status/1162601447235604480?lang=en https://twitter.com/elonmusk/status/1162601447235604480?lang...
baybal2 7y ago
Imagine the autoclave the size of a rocket. Composite tanks on few rockets being flown with them are made in one of a kind, purpose built autoclaves
- greglindahl 7y ago
  Out-of-autoclave methods are mature and common these days.
  - baybal2 7y ago
    Do they get you the same strength, fill ratio, and allow for usage with aerospace specialty epoxies?
elihu 7y ago
He also talked about how stainless steel has a high melting point (which means their re-entry heat shield doesn't need to be as thick) and gets stronger rather than weaker at very low temperatures.
emilecantin 7y ago
As he said in the presentation, it was because at cryogenic temperatures (which is the important part when you're building a liquid oxygen / methane tank) 301 stainless is actually _stronger_ than Al / carbon fiber. It also handles heat much better, which allows you to have a much thinner heatshield. Both characteristics combine to give a lighter rocket than one built out of Al / carbon fiber. The price is just the cherry on top.

HenryKissinger 7y ago

It reminds me of the F-104 Starfighter: https://upload.wikimedia.org/wikipedia/commons/d/de/Lockheed_XF-104_%28modified%29.jpg https://upload.wikimedia.org/wikipedia/commons/d/de/Lockheed... Or the F-86 Sabre: https://upload.wikimedia.org/wikipedia/commons/3/39/F86F_Sabres_-_Chino_Airshow_2014_%28cropped%29.jpg https://upload.wikimedia.org/wikipedia/commons/3/39/F86F_Sab...

chr1 7y ago
Is the surface of these less smooth than surface of normal rockets/planes, or is it simply the effect of mirror like surface making bumpiness easier to see?
- skykooler 7y ago
  The latter - a matte surface would be lit from essentially the same angle, but even a tiny discrepancy causes big shifts in a reflection.

mattlondon 7y ago

I am totally with you on this - I just can't get over how utterly rudimentary and basic this thing looks! I can't wait to see it fly! I am so used to seeing space stuff done in clean rooms, and things taking years and years to come to fruition (e.g. hearing about and seeing NASA or ESA probes etc getting made) that to see what is essentially a bunch of guys in a field just welding something together blows my mind. I mean, is it just the outside that looks like that and inside it is ultra-exotic materials and tanks? Of course the engines are sophisticated machinery, but what about the insides? Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside?

extrapickles 7y ago
I suspect most of the structure that gets really hot or cold is steel. To save weight, they are probably also letting more of the rocket get colder/hotter than normal, thanks to the wider temperature range of steel. Once the temperatures get reasonable, it might be aluminum or or carbon fiber. The passenger/cargo/avionics section are probably the only areas where this would be true, so a bulk of the rocket will be steel.
- hinkley 7y ago
  Steel can tolerate a lot more deflection before it bends, and much more stress before it cracks. And while I would never expect a space craft mechanic to employ this technique, any bike mechanic will happily offer to bend steel back into shape for you, but bent aluminum or carbon fiber is scrap. Bending it back will fracture it, if it hasn't already. When Canondale hit the big time, they had one model year where they made the dropouts out of solid aluminum and in the next model year the derailleur hanger was bolted on. It's the easiest part to bend and there's no repairing it. Bad enough for road bikes, spectacularly dumb for mountain bikes.
balfirevic 7y ago
> Are we just seeing the outer shell and it's all unobtanium nano-tube composite on the inside? Nope, it's just steel. Outside shell is the tank.

Florin_Andrei 7y ago

> the welded together steel plates really make me think of the sort of thing Wallace and Gromit would build The most beautiful thing in the world is success.

deleted 7y ago

[deleted]

iamgopal 7y ago

We work with multiple tens of ton of SS steel per month, and I would have never thought this heavy thing could fly with all the stress of the sky. I hope it fly good.

de_watcher 7y ago

Scrapped together plates make you wonder how it won't fall apart on ascent or descent...