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Elon Musk Explains Why He's Building 'Starship' Out of Stainless Steel (popularmechanics.com)
Long-time Slashdot reader darkwing_bmf writes: In an exclusive interview with Popular Mechanics, SpaceX founder Elon Musk explains why stainless steel is the best material to build rocket ships, beating carbon fiber in cost, durability and even weight.
"As far as we know, this marks the first time the material has been used in spacecraft construction since some early, ill-fated attempts during the Atlas program in the late 1950s," reports Popular Mechanics.
"It took me quite a bit of effort to convince the team to go in this direction..." Musk tells them. But among the other benefits "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... But steel, you can do 1500, 1600 degrees Fahrenheit."
"As far as we know, this marks the first time the material has been used in spacecraft construction since some early, ill-fated attempts during the Atlas program in the late 1950s," reports Popular Mechanics.
"It took me quite a bit of effort to convince the team to go in this direction..." Musk tells them. But among the other benefits "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... But steel, you can do 1500, 1600 degrees Fahrenheit."
I was frequently Debbie Downer about using CF for BFR. It's not a resilient material, and organics don't play well with LOX, nor does CF like operating at cryogenic temperatures; you're fighting against its innate material properties. I love the use of stainless. It's so much more forgiving, and people who know how to work with it are a dime a dozen. Just everything about this design will be so much easier. And cheaper. And faster. And safer.
I wouldn't be surprised if they outright build Starship and Super Heavy outside, shipyard-style. It wouldn't exactly be the first time giant pressuretight steel vessels designed for dealing with harsh conditions were built outside in salt-air conditions (e.g., almost every refinery on Earth). Corrosion rates in marine environments are on the order of decades to centuries per millimeter, depending on the stainless alloy (unlike alumium which is sensitive to salt) - and galvanic corrosion due to junctions with dissimilar metals (such as alumium) tend to corrode the other metal, not the steel (again, unlike alumium). There should be no issues with an under-construction rocket shell sitting outside for months until they can get it enclosed for more sensitive work on the interior. The LOX tank would need to be well cleaned, mind you, since LOX doesn't play well with contaminants (CH4 isn't particularly sensitive), and as always, welds need to be properly inspected.
It's an unconventional choice, but one which I've been really glad to see.
"Are you hungry? I haven't eaten since later this afternoon." -- Primer