For rather obvious reasoons, the diving through the Titanic is acceptable, but not diving in or even close to the Lousitania. There is still fear, someone could discover munition inside...
OceanGate Expeditions Titan DSV loss
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For rather obvious reasoons, the diving through the Titanic is acceptable, but not diving in or even close to the Lousitania. There is still fear, someone could discover munition inside...
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Lusitania divers warned of danger from war munitions in 1982, papers reveal
Foreign Office warning that operation 'could literally blow up on us' reopens debate over German rationale for sinking liner
No evidence of artillery type munitions has surfaced.
Because it is forbidden to search for it. There is and has allways been strong indication of amonition on board, thats why the German Goverment strongly reomended not to use this ship. Meanwhile, Brits admitted that there is indeed amonition on the ship, but they state it would be empty shells, which would have been a civil product by definition of that time. Now the wreck is sealed and diving around is forbidden, unlike diving around and inside any other ship, no matter how many people died during the wreckage.
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There have been many dives on Lusitania and the only things found were small arms and some shell cases, contested identity at that.
Far too many conspiracy theories and Ockhams razor applies. The dive that was refused permission was looking for artworks sealed in lead boxes and owned by Sir Hugh Lane.
More a case of using the hyperbole of supposed munitions to get at a haul of art worth quite a bit if the lead boxes and seals hel out.
Everybody has an angle.
www.irishtimes.com
Far too many conspiracy theories and Ockhams razor applies. The dive that was refused permission was looking for artworks sealed in lead boxes and owned by Sir Hugh Lane.
More a case of using the hyperbole of supposed munitions to get at a haul of art worth quite a bit if the lead boxes and seals hel out.
Everybody has an angle.
Irish diving team finds munitions on wreck of the 'Lusitania'
An Irish diving team has discovered munitions on board the wreck of the Lusitania, which was sunk by a German submarine off the…
There would of course have been a logic to leaving the rubble pile, so long as you use it for proper political, cultural and educational purposes. "This rubble pile, and all the misery associated with it, was brought to you by..." Same reason why Auschwitz is kept, so that people don't forget that some ideologies are awful and should be excluded not just from polite society, but from the country.
A bit beyond the point of the sub, though. There are bits and pieces in and of the Titanic that could and arguably should be recovered... ceramics (plates and cups and such), jewelry, bronze, glass. That sort of stuff will last longer than civilization. But iron is going away quickly, and human remains long ago vanished. Even bones and teeth dissolved away:
Carbonate compensation depth - Wikipedia
Soon enough, the Titanic will be a couple large patches of rusty muck covering a bunch of dinnerware, with three large bronze propellers at one end. Those props would be a chore and a half to recover, but they'd make a fine museum display. The argument that the Titanic should be left as a memorial is difficult to square against the fact that it is and will long remain damn near unreachable, while an on-shore memorial could be visited by millions annually. Additionally, we're well past a century beyond the event; there are no survivors. Another 70 or so years and there will be nobody left who ever met a Titanic survivor. Memorials are for the living, not the dead... and when the living are sufficiently separated from the dead, the dead don't get memorialized. Otherwise the Vasa would have been left at the bottom of the harbor, the Oseburg longship left in its grave.
*Sort* *of.* DC-X hovered, burning lots of propellant as it rather gingerly lowered itself to the ground. Falcon "hoverslams," where it plummets like a stock market straight out of the sky and only ignites the engine at the last possible second, burning with all its might on a trajectory calculated to bring it to zero velocity relative to the ground right when it reaches the ground. This is a *fantastic* way to save propellant, but it is fuckup-intolerant. Still, they've done it hundreds of times in a row. They will doubtless lose one again, but their string of success have been remarkable.
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The text/narrative appears to be the same as another known fake, just tidied up to match the style of some authentic chats seen in a video. So, presume fake as well.
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hagaricus
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Fair enough, spooky reading anyhow.
A former OceanGate advisor said the Titanic submersible tried to reach the surface before it imploded, indicating those on board knew something had gone wrong
Rob McCallum said the Titan dropped its weights and was trying to ascend before it lost communication with its mother ship.
Could be real, guess time will tell.
Regards,
Ok, even with the thing being a fake, it makes me wonder. The composite hull crushed like an egg, because it didn't whistood the pressure anymore - POOF.
What I'm wondering is two things
-would the composites give any warning they were giving up to the pressure ? a few noise or CRAAAACK, thing like that ?
-could the composite give up because they were compromised (tainted ? contaminated) by saltwater ? a bit like rusty steel being corroded by saltwater, turns red, small flecks fall, that kind of thing...
What I'm wondering is two things
-would the composites give any warning they were giving up to the pressure ? a few noise or CRAAAACK, thing like that ?
-could the composite give up because they were compromised (tainted ? contaminated) by saltwater ? a bit like rusty steel being corroded by saltwater, turns red, small flecks fall, that kind of thing...
shedofdread
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Has anything been written about the fibre orientation of the lay up used to create the 'pipe' section of the vessel From what I've seen, it looked to be a tube with integral flanges at each end.
I could imagine a scenario whereby the repeated pressure cycles could've caused some very minor cracking in the protective surface coating in the region where the 'tube' meets the 'flange'. The flange area being stronger than the tube. Osmosis would then occur in that region further weakening the structure.
Speculation - the occupants probably heard a second or so of cracking noises before..... well....
Composites form a good half of work and everything about the structure of that craft looks like a bad idea.
All very sad and unnecessary.
I could imagine a scenario whereby the repeated pressure cycles could've caused some very minor cracking in the protective surface coating in the region where the 'tube' meets the 'flange'. The flange area being stronger than the tube. Osmosis would then occur in that region further weakening the structure.
Speculation - the occupants probably heard a second or so of cracking noises before..... well....
Composites form a good half of work and everything about the structure of that craft looks like a bad idea.
All very sad and unnecessary.
Scott Kenny
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IIRC, a video showed a wrap at a pretty significant angle to the tube, like how most composite pressure cylinders are made.
shedofdread
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The problem being is that at that angle, it's really not good when loaded in the way that a submersible is. Tragic, really.
Scott Kenny
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Not sure that any angle would have been better. Parallel to the tube would have at least put more of the CF in tension, but then it'd be prone to cracking along the length. Perpendicular to the tube would have been the worst option, CF in compression and likely to shear perpendicular to the length into nice CF rings.
CF is just terrible in compression, full stop.
Go tell that to Stock market... Stockton Crush... Rush, who was seemingly smarter than everyone else, including the entire universe... he was smarter than compression, you see.
Stockton: he wanted to rush, he ended in a crush.
Scott Kenny
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Fools and their money are soon parted.
Every time you bend a part made out of Carbon fibre, about half of the fibres will go into compression. The upper side of a carbon fibre wing is usually under compression and it works fine. I do agree, that it is not a good idea to press on the endings of a carbon fibre. Carbon fibre push rods, which have been promoted as tuning article for OHV engines, often turned in to black dust because the carbon fibre tubes had open carbon fibre endings put into metallic end caps (just like in the Titan).
In the Titan design, the radial loads could be easier dealt with carbon fibres than the longitudinal loads. I have no idea on how to wind up the carbon fibres so that the axial loads can be efficiently carried into a longitudinal orientation.
Another main problem in the attachment between the carbon fiber tube and the Titan end caps is the different elasticity in the parts, which mean they will contract differently under pressure. Also mind, the carbon fibers shall never be in contact with the water (danger of delamination!), so that the relative soft plastic material has to transfer all the loads on the attachment points.
In the Titan design, the radial loads could be easier dealt with carbon fibres than the longitudinal loads. I have no idea on how to wind up the carbon fibres so that the axial loads can be efficiently carried into a longitudinal orientation.
Another main problem in the attachment between the carbon fiber tube and the Titan end caps is the different elasticity in the parts, which mean they will contract differently under pressure. Also mind, the carbon fibers shall never be in contact with the water (danger of delamination!), so that the relative soft plastic material has to transfer all the loads on the attachment points.
Scott Kenny
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Exactly.
It's like he saw the very impressive tensile strength of CF and never thought to ask WHY no one was using it in submersibles, or at least not more than once.
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Even after professionals who actually design submersibles sought him out to explain it using very small words ...
_Del_
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I agree, but with a major caveat.
I don't think it's particularly crazy to use composites in such a case. It should be the sort of thing people are interested in testing. Different patterns and materials tested at depth makes fine sense to me. Doesn't even bother me that he used out of spec commercial aviation material. Everyone after a five minute primer would understand what problems are going to likely pop up. If you want to try to find something that works in spite of that, go for it.
What is absolutely crazy is making a commercial diving program using the same carbon fiber elements repeatedly. If he wanted to brave the unknown testing this stuff, ignoring safety standards, then I'd give him a round of posthumous applause while looking sideways at the level of foolhardiness/madness many such explorers possess. When you start selling seats on such a venture, however, you are implying a base-level of safety that did not exist.
Go down, test the vessel over multiple trips, preferably without a crew. Drop it down on a tether. Let the weight-attachments disolve after X-hours. Recover it and pour over it. Could have done an exhaustive autopsy on the material after one dive cycle. Then two cycles. Then three. Then four, until you get a handle on what is happening to your fibres and what cracking, delam, and debonding is taking place in these cycles. But that would take money.
Should be testing it to destruction to be honest. Heaven knows how many things and components of things I've had to test to destruction.
It might be entirely possible to bond a composite section good for two or three (or even four or five or a dozen) trips to titanium or steel endcaps. It might even wind up being cheaper than a steel/titanium pressure vessel if the processes were proven and you were making enough trips to make the economies of composite section production and assembly scale up (but I doubt it). You would have to find that particular pattern and thickness that works well for your application, and whatever bonding process, first -- and it probably isn't the combination you decided to take a SWAG on for your first batch.
I do think he was perfectly reasonable looking at the application. I think it's great, in fact. It's like the game controller. That is the least concerning thing about this. What's concerning is that he would risk his, and worse, others' lives testing an experimental vessel in a commercial venture. But exploring the composite use case is perfectly reasonable at face value. I'd be stunned if the Navy, for instance, has not conducted many, many tests with results sitting in a file somewhere buried never to see the light of day. (I'd be stunned if they had an affordable and reuseable composite submarine pressure vessel, too, but I'm sure they've tried a hundred different ways to do it).
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They did. They did a series of (manned) test dives in 2018/2019. There were structural problems found with the pressure vessel. Crew heard creaking/cracking. In response they built a new pressure vessel and added their "health monitoring" system.
There are descriptions of how the original pressure vessel was constructed up thread (Composites World article, etc). It was constructed by the same company that build the DeepFlight Challenger pressure vessel - which was never used deeper than a few meters but was extensively tested onshore, and certified by DeepFlight for ONE deep dive.
The second pressure vessel, which is what was used after 2019, we know little about. It may have been constructed the same way, it may not have. It was not tested in onshore facilities like the first one supposedly was, and it did not go through a series of test dives like the first did. Essentially every paid "expedition" was a test dive.
Carbon *could* be a good material for submersible pressure vessels. It just has not been used or tested extensively enough yet for manned vessels. There are too many unknowns. Carbon is being used for some ROV pressure vessels, but the company that makes those isn't confident they should be used for manned vehicles.
At the end of the day, were the supposed advantages of using carbon worth the risks that come with using a new, untried material in the deep ocean? Apparently not. The advantages of carbon that OceanGate has stated revolve around weight and not having to use "expensive" syntactic foam for bouancy. I can't see how using foam and steel or titanium would cost more than having a large carbon pressure vessel.
martinbayer
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And sometimes their lives as well.
_Del_
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That's all my point, really. If this guy wanted to risk himself trying something foolhardy, more power to him. The potential pitfalls are pretty clear, but it's not impossible he stumbles upon something useful -- perhaps even commercially viable. He's not the only one interested, and it is probably viable in one form or another.
The only distressing part to me is that he chose to sell tickets implying a much higher level of confidence than should have ever existed. Particularly over multiple cycles. If we're going to lambast him, that's the angle. I don't particularly care if he puts himself at the helm of such a craft and wants to dive in a composite hull multiple times. That part seems crazy to me, but is conceivably doable. Borders on laudable until he took people with him on a commercial dive. It is then he crosses the line from "material-science pioneer aquanaut" to "huckster madman".
Too many people taking the low-hanging fruit of "Ha He used composites". Like I said before, the potential pitfalls are obvious, but you don't get anywhere on that without data, and to get data, someone has to build and test it. If he was confident enough to put himself at risk, more power to him. I certainly wouldn't be, but I wouldn't try the Shackleton Expedition either. Hell, I wouldn't have been too keen on getting on an Osprey for the first decade or two. People brave/foolish enough to test limits isn't really the angle I would attack the man.
I know nothing about syntactic foam beyond a quick google search for cost that lists the rate between $500-$1000 per cubic foot. If I shave a 1000 lbs of weight by using composites, depending on the foam densities involved, I could see the dollars adding up quick. Perhaps enough to make a commercial case.
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Just in DeepFlight Challenger as a pressure vessel, and that was only rated for ONE deep dive.
Lots of use in full size submarines in a free flooding area so that it's not under compression. Periscope fairings,
No, we know that carbon fiber is terrible for an inverse pressure vessel, one where the high pressure is outside and compressing the vessel.
Carbon fiber has been known to be terrible in compression loads, since basically the beginning of Carbon Fiber anything.
Carbon fiber excels in tension applications.
You would need access to some exceptionally good welders, plus X-raying all the welds in a 10"+ thick steel section. And IIRC doing some scary levels of pre-heating the HY100 steel before welding, 140+degF.
It may have been possible to contract with the Bremerton naval shipyard, to have them build the steel submersible. They have the skilled welders and everything else to properly weld HY100 steel. But it would not have been cheap.
OliverSedlacek
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Race cars have used carbon fiber in compression in suspension push rods and wishbones. Mind you, it took them years to feed the loads in to metal end pieces reliably.
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Admittedly, without looking at how they do it specifically, the way you use carbon in compression in a strut or rod is not how you'd use it in a pressure vessel.
While rigid, a carbon column would use tensegrity.
General description here:
Tensegrity - Wikipedia
In the case of direct linear loads, it works this way. A tubular column under compression along its axis will buckle, hopefully outwards. This increases its diameter at the mid point but more importantly it increases its circumference. This is where the tensile strength of carbon fibre comes into play, resisting that expansion. It's a damned clever trick, but it's not applicable to keeping pressure from all directions crushing a tube, because that imposes bending forces radially and compression circumferentially.
OceanGate was trying to make what was effectively a 360 degree vault or arch to resist external loads. Shear resistance between the layers of carbon fibre in the resin matrix was supposed to prevent bending at any point in the circle giving, so to speak, second-hand compression strength. The moment there was any asymmetry in the circle due to fatigue or delamination, it would buckle.
Have a look at the example on the left for an illustration.
Attachments
martinbayer
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It really does not matter much how they conceived the design, but what really matters is that they did not follow proper engineering protocol in testing, verifying, validating, and certifying that design.
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OliverSedlacek
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Struts in compression fail at the critical Euler load, https://en.wikipedia.org/wiki/Euler's_critical_load
Agreed, this doesn't apply to pressure vessels.
Agreed, this doesn't apply to pressure vessels.
martinbayer
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I hear a book on this unfortunate event is already in the works - "Unsound At Any Depth" by Ralph Nadir. I'll see myself out...
Brilliant ! Made me chuckle...
FighterJock
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A book out already? That is a bit quick, cashing in springs to mind. 
martinbayer
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I was kidding - look at the title and (slightly misspelled) author name, and see https://en.wikipedia.org/wiki/Ralph_Nader...A book out already? That is a bit quick, cashing in springs to mind.
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FighterJock
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Ah! right now I get it.
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