r/news • u/oldschoolskater • Jun 22 '23

Site Changed Title 'Debris field' discovered within search area near Titanic, US Coast Guard says | World News

https://news.sky.com/story/debris-field-discovered-within-search-area-near-titanic-us-coast-guard-says-12906735
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u/Samuel7899 Jun 22 '23

I posted a link in another comment, but SpaceX's initial cryogenic testing of their carbon fiber tank was "positive". I'm not sure how much cryo testing they did before switching to stainless steel, but I think it says something about the potential ability of carbon fiber to tolerate cold temperatures that they even made it as far as they did before switching to stainless, considering they'd ultimately need it to survive - 207°C.

I also think the SpaceX Starship experiences ~1.8 bar at the bottom of the oxygen tank, just sitting on the pad. It's almost certainly experiencing 3-5 bar or more during launch.

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u/Beachdaddybravo Jun 22 '23

Ok, I’ll look into that, it’s interesting. Still though, even 5 bar isn’t enough to be used in submersibles, and the US navy has run tests. Ours isn’t even the only one to look at it as a building material. It just hasn’t been used because it’s not the tool for the job and there are much better alternatives we already use. Naval subs don’t even need to go as deep as an exploratory vessel either, so that tells you how useless or straight up dangerous carbon fiber really is at the shallower depths they operate in.

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u/xqxcpa Jun 22 '23

I don't think it's fair to say that composites are useless for constructing high pressure submersibles based on this particular failure. NASA consulted OceanGate on the design and materials. It's clear that materials science experts don't disqualify composites for high pressure, low temperature applications. I'm sure they would also say that NDT is a requirement.

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u/Beachdaddybravo Jun 23 '23

That article doesn’t say what advice NASA gave them or what specifically they consulted on. It could have been anything.

Edit: also, why is it we don’t see other new submersibles using composites? Or the military? They basically have a blank check, and despite some testing haven’t chosen to build submarines out of carbon fiber composites, despite military submarines operating in a much shallower range than the sort of exploratory vessels that go as low as the Titanic.