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posted by martyb on Wednesday January 23 2019, @03:39AM   Printer-friendly
from the SHINY! dept.

Popular Mechanics has interviewed SpaceX CEO Elon Musk about his decision to move to a stainless steel design for Starship Super Heavy (formerly BFR). The interview reveals new details about the design, including micro-perforations on the outside of the windward side of the rocket that can bleed water or fuel for cooling:

Ryan D'Agostino: How does stainless steel compare [to carbon fiber]?

Elon Musk: The thing that's counterintuitive about the stainless steel is, it's obviously cheap, it's obviously fast—but it's not obviously the lightest. But it is actually the lightest. If you look at the properties of a high-quality stainless steel, the thing that isn't obvious is that at cryogenic temperatures, the strength is boosted by 50 percent.

Most steels, as you get to cryogenic temperatures, they become very brittle. You've seen the trick with liquid nitrogen on typical carbon steel: You spray liquid nitrogen, you can hit it with a hammer, it shatters like glass. That's true of most steels, but not of stainless steel that has a high chrome-nickel content. That actually increases in strength, and ductility is still very high. So you have, like, 12 to 18 percent ductility at, say, minus 330 degrees Fahrenheit. Very ductile, very tough. No fracture issues.

[...] [Here's] the other benefit of steel: It has a high melting point. Much higher than aluminum, and although carbon fiber doesn't melt, the resin gets destroyed at a certain temperature. So typically aluminum or carbon fiber, for a steady-state operating temperature, you're really limited to about 300 degrees Fahrenheit. It's not that high. You can take little brief excursions above that, maybe 350. Four hundred, you're really pushing it. It weakens. And there are some carbon fibers that can take 400 degrees Fahrenheit, but then you have strength knockdowns. But steel, you can do 1500, 1600 degrees Fahrenheit.

[...] 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.

The steel used will be about $3/kg vs. $135/kg ($200/kg assuming a 35% scrap rate) for carbon fiber.

Also at Futurism.

Previously: SpaceX's Starship Will Now be Made of Stainless Steel, With Tests Still Scheduled for Early 2019

Related: SpaceX to Purchase $2 Billion of Carbon Fiber Sheets
SpaceX Reveals Plan to Fly Yusaku Maezawa and Artists "Around the Moon" in a BFR


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  • (Score: 0) by Anonymous Coward on Wednesday January 23 2019, @06:56AM (4 children)

    by Anonymous Coward on Wednesday January 23 2019, @06:56AM (#790488)

    Sell it to Space Force. They won't ask a lot of questions if it sounds cool.

  • (Score: 2) by takyon on Wednesday January 23 2019, @07:36AM

    by takyon (881) <takyonNO@SPAMsoylentnews.org> on Wednesday January 23 2019, @07:36AM (#790505) Journal

    Giving money to SpaceX doesn't enrich the usual suspects.

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    [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
  • (Score: 2) by c0lo on Wednesday January 23 2019, @07:37AM (2 children)

    by c0lo (156) on Wednesday January 23 2019, @07:37AM (#790507) Journal

    They won't ask a lot of questions if it sounds cool.

    Steel - so past millenium, how can it be cool? I mean, look, no nano- meta- or -phobic material, no blockchain, no CRISPR-x, no nothing, not even jobs.

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    • (Score: 0) by Anonymous Coward on Thursday January 24 2019, @12:16AM

      by Anonymous Coward on Thursday January 24 2019, @12:16AM (#790935)

      Orangium.

    • (Score: 2) by realDonaldTrump on Thursday January 24 2019, @05:06AM

      by realDonaldTrump (6614) on Thursday January 24 2019, @05:06AM (#791058) Homepage Journal

      I hear that Steel is the future. We love Steel -- so long as it's American Steel. Our Steel Industry is the talk of the World. It has been given new life, and is thriving. Because of me. I hired Wilbur Ross, one of our biggest Steel Men. He said, do the Tarriffs, we need Tarriffs. And I moved very strongly on those. Tarriffs have had a tremendous positive impact on our Steel Industry. Plants are opening all over the U.S., Steelworkers are working again, and big dollars are flowing into our Treasury. Into the coffers of our Country. Other countries use Tariffs against, but when we use them, foolish people scream. America First!!