Stainless steel spaceships... Elon Musk using 301 ss!?!

D

dirc

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So, as many of us, I'm into steel and metallurgy and have been since I was a young kid. (the benefits of having a dad who worked at the large steel mill for 40 years)

Elon Musk's spaceship is stainless steel ;)
https://arstechnica.com/science/2019/01/elon-musk-is-really-really-excited-about-his-starship/

some of his tweets:
  • The vehicle's exterior will be made from a stainless-steel alloy that will not buckle and will remain stable on the launchpad even when unpressurized. The strength and weight of "full hard stainless" at cold temperatures is slightly better than carbon fiber, at room temperature it is worse, and at high temperature it is vastly better.
  • The metallic skin of Starship will get too hot for paint, so it will have a stainless mirror finish. It will need much less shielding as a result, and areas that take the brunt of atmospheric entry heating will be activity cooled with residual liquid methane. As a result, "Starship will look like liquid silver."

So, what's your best guess about the composition of his ss?
I hope Larrin Larrin sees this :)

My guess, If I had to make one... is something like 316H ? It's high strength and temp... only about 0.1% carbon, and 10-14% nickel, 2-3% moly

Anyway, I look forward to hearing info/updates/news about this. If anyone has knowledge of better structural ss, please share : )
 
you think 316H or a similar variant is most likely? Or is there some newer nitrogen variant of this grade/class of ss?
 
Probably some boring stainless steel. Full hard just means it's cold rolled material. It's not really my area though.
 
Hardly boring - I thought it existed (nitrogen structural ss), and I was right; it's called DUPLEX 2205 http://jamesduva.com/wp-content/uploads/2017/08/JDI-material-2205-specification-sheet.pdf
"2205 is a ferritic-austenitic stainless steel which combines many of the beneficial properties of both ferritic and austenitic steels."

Tensile Strength (KSI) 65
Yield Strength (KSI) 90 (this is about 2 or 3 times higher than 316 ss)

C 0.03
Cr 21-23
Fe Bal
Mn 2.0
Mo 2.5–3.5
N 0.08–0.20
Ni 4.5–6.5
P 0.03
S 0.02
Si 1.0
 
Pipe dream. (literally, since 2205 is typically used for pipe.)
If stainless steel were really a viable option, aircraft would have stainless steel skins.
It isn't.
They don't.
Too heavy.
upload_2019-1-9_21-26-15.png
1.4 times as strong as 2024T351 aluminum.
2.8 times as heavy.
half again as strong, weighs three times as much.
That's what we call a "no fly".
 
dirc said:
So, as many of us, I'm into steel and metallurgy and have been since I was a young kid. (the benefits of having a dad who worked at the large steel mill for 40 years)

Elon Musk's spaceship is stainless steel ;)
https://arstechnica.com/science/2019/01/elon-musk-is-really-really-excited-about-his-starship/

some of his tweets:
  • The vehicle's exterior will be made from a stainless-steel alloy that will not buckle and will remain stable on the launchpad even when unpressurized. The strength and weight of "full hard stainless" at cold temperatures is slightly better than carbon fiber, at room temperature it is worse, and at high temperature it is vastly better.
  • The metallic skin of Starship will get too hot for paint, so it will have a stainless mirror finish. It will need much less shielding as a result, and areas that take the brunt of atmospheric entry heating will be activity cooled with residual liquid methane. As a result, "Starship will look like liquid silver."
So, what's your best guess about the composition of his ss?
I hope Larrin Larrin sees this :)

My guess, If I had to make one... is something like 316H ? It's high strength and temp... only about 0.1% carbon, and 10-14% nickel, 2-3% moly

Anyway, I look forward to hearing info/updates/news about this. If anyone has knowledge of better structural ss, please share : )
Click to expand...

Definitely 8cr13mov.
 
Budd RB-1 Conestoga.

https://en.wikipedia.org/wiki/Budd_RB_Conestoga

Made by the same company that built the Zephyr train, the company that also pioneered "shot welding" of stainless steel. Designed and made during WWII in anticipation of an aluminum shortage that might cripple the war effort. Originally 200 were ordered, but the supply of aluminum held out, and the order was cut to 25, and only 17 were delivered.

Only one survives, basically derelict, baking in the desert sun about 10 miles from me.

Budd.jpg

OK, it's not a spaceship. It wasn't even pressurized. But they made a stainless steel production aircraft in 1943, and as you can see it's not a pile of rust.
 
Planterz said:
Budd RB-1 Conestoga.

https://en.wikipedia.org/wiki/Budd_RB_Conestoga

Made by the same company that built the Zephyr train, the company that also pioneered "shot welding" of stainless steel. Designed and made during WWII in anticipation of an aluminum shortage that might cripple the war effort. Originally 200 were ordered, but the supply of aluminum held out, and the order was cut to 25, and only 17 were delivered.

Only one survives, basically derelict, baking in the desert sun about 10 miles from me.

View attachment 1051420

OK, it's not a spaceship. It wasn't even pressurized. But they made a stainless steel production aircraft in 1943, and as you can see it's not a pile of rust.
Click to expand...
Judging by the wrinkles, that's a REALLY thin skin...way thinner than I'd think a pressurized vessel would need.

~Chip
 
knarfeng said:
Pipe dream. (literally, since 2205 is typically used for pipe.)
If stainless steel were really a viable option, aircraft would have stainless steel skins.
It isn't.
They don't.
Too heavy.
View attachment 1051388
1.4 times as strong as 2024T351 aluminum.
2.8 times as heavy.
half again as strong, weighs three times as much.
That's what we call a "no fly".
Click to expand...

Well, good thing it's not an airplane... it's a space ship that will experience MUCH higher temperatures, and thus the extra weight in using ss is acceptable. Most aluminum alloys rate mechanical strength up to about 380F... I think they're planning on going double or triple that temp. Stainless Steel will retain strength at far higher temps.
 
Last edited:
dirc said:
Well, good thing it's not an airplane... it's a space ship that will experience MUCH higher temperatures, and thus the extra weight in using ss is acceptable. Most aluminum alloys rate mechanical strength up to about 380F... I think they're planning on going double or triple that temp. Stainless Steel will retain strength at far higher temps.
Click to expand...

True. Wasn't looking at reentry.
But steel still won't take the heat of reentry. Stainless tops out at about 1200F to remain structural. To go higher you need nickel alloys. The shuttle skin saw 3000F. The amount of methane necessary to cool the skin to a temperature at which steel would retain its strength would be enormous. I have a hard time believing that "residual" methane from the launch fuel would be sufficient.
 
Elon's on crack. He's graduated up from pot.
I'll bet he wishes he could take that huff and puff, back.
 
HOLY sh*t - it's basic 301 stainless he's using??? wtf?

https://www.popularmechanics.com/space/rockets/a25953663/elon-musk-spacex-bfr-stainless-steel/

RD: Do you have a whole metallurgy team here?
EM: We do have a great materials group, but initially we will simply use high-quality 301 stainless. There’s an important other thing that makes a big difference. For ascent you want something that’s strong at cryogenic temperatures. For entry, you want something that can withstand high heat. So the mass of the heat shield is driven by the temperature at the interface between the heat shield tiles and the air frame. Whether it’s mechanical or if it’s bonded on—whatever the interface point is—determines the thickness of the heat shield.

On the Dragon, for example, the thickness of the heat shield tiles is actually driven by the heat soak from the heat shield getting to the bond line of the tile onto the shell. So it’s not driven by erosion of the tile. It’s actually driven by conductivity of the tile to the bond line so we don’t lose tiles as it’s descending under a chute. You don’t want to be tossing tiles off, basically.


With steel, now you’ve got something where you can comfortably be at a 1500 F interface temperature instead of, say, a 300 F, so you have five times the temperature capability at interface point. What that means is that for a steel structure, the leeward side of the back shell does not need any heat shielding.

On the windward side, what I want to do is have the first-ever regenerative heat shield. A double-walled stainless shell—like a stainless-steel sandwich, essentially, with two layers. You just need, essentially, two layers that are joined with stringers. You flow either fuel or water in between the sandwich layer, and then you have micro-perforations on the outside—very tiny perforations—and you essentially bleed water, or you could bleed fuel, through the micro-perforations on the outside. You wouldn’t see them unless you got up close. But you use transpiration cooling to cool the windward side of the rocket. So the whole thing will still look fully chrome, like this cocktail shaker in front of us. But one side will be double-walled and that serves a double purpose, which is to stiffen the structure of the vehicle so it does not suffer from the fate of the Atlas. You have a heat shield that serves double duty as structure.

Yeah.

To the best of my knowledge this has never been proposed before.

RD: This is a huge change.
EM: Yes.

RD: Where will the steel come from?
EM: It’s just 301 stainless. Let me put it this way: 304 stainless is what they make pots out of. There’s plenty of it.
 
Stainless SUCKS ! ! !
Only M4 is any good ! ! !

. . . oh . . . wait . . . this isn't that kind of thread.
Neeeeeevermind.

Heck I don't know. Most structural SS is almost nonmagnetic right ?
I would be interested to know if what he is using is that or is more on the magnetic end of the spectrum.

One of my weaknesses is watching old ('40s, '50s, '60s) crappy Sci Fi movies with "tin can" space ships.
Invariably they busssout the magnetic soled boots to keep the crew from floating around the ship or to walk on the outside of the ship for EVA.

I always have to fidget a bit when I see that.
 
well, only 3 elements are normally magnetic (in steel use), iron, nickel & cobalt - thats it ... it's funny how you end up using one of those to make it non-magnetic:

you need high chrome (18%) and nickel (8%) to get a face-centered cubic (fcc) - which is the structure to make it non-magnetic (aka austenitic)
(some other elements can be used to make fcc structures, but as usual, the rabbit hole is deep on this aspect of steel)
 
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