Titanic tourist sub missing

Gord_in_Toronto said:
A sort of update. But not much new.

Canada was 'highly confident' it heard man-made noises during search for Titan submersible, documents show | CBC News
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Provocative headline, later in the article there is a dose of reality.


"He said it's "very common" for sonar operators to hear mechanical noises underwater, and the banging detected heard could have been coming from oil rigs off the coast of Newfoundland, a submersed pipeline, or other vessels."


I have more confidence in the original detection of the implosion, especially since it coincided with a loss of communication.
 
Latest news:

'All good here': Last messages revealed from Titan submersible before implosion: Coast Guard

The Marine Board of Investigation for the U.S. Coast Guard's two-week hearing into the incident began on Monday, 15 months after the OceanGate vessel catastrophically imploded during its deep-sea voyage, killing all five people aboard.
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Not much new but some additional details.

I do note though hat:
The last communication from the submersible was sent at approximately 3,341 meters: "Dropped two wts," meaning drop weights, according to the Coast Guard.

All communications and tracking from the submersible to Polar Prince were lost at 3,346 meters, according to the Coast Guard.
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The loss so close to the weight dropping is a little suspicious. Maybe a connection?
 
I'm not a material sciences engineer, but to put things into perspective, the thing was already under the pressure equivalent of the weight of an older aircraft carrier per square inch. I doubt that the small jolt was anything else than lost in the decimals at that point. If the thing had enough safety margin, it wouldn't matter at all. Plus, think of it this way: by the time they'd actually reach the bottom, the increase in pressure would be even higher, so it would be doomed anyway.
 
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HansMustermann said:
I'm not a material sciences engineer, but to put things into perspective, the thing was already under the pressure equivalent of the weight of an older aircraft carrier per square inch. I doubt that the small jolt was anything else than lost in the decimals at that point. If the thing had enough safety margin, it wouldn't matter at all. Plus, think of it this way: by the time they'd actually reach the bottom, the increase in pressure would be even higher, so it would be doomed anyway.
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Nope, nothing even close to that. A typical WW2 carrier was about 25,000 tons give or take 5,000 (51 million pounds ± 11 million pounds). The pressure under 3350m of seawater is around 4,900 psi, (about 2½ tons per square inch). Its more like the weight of a pickup truck per square inch.

Still a "shipload" of pressure though.
 
AH, right, that was the total force all around the sub, not per square inch. Thanks for the correction.
 
Reading the news reports coming from the investigation it appears that the whole enterprise was pretty much the cluster **** that had been surmised.

Megalomania reigned supreme.
 
Skeptical Greg said:
Could the sudden change of speed, with the dropping of the weights, have been the proverbial straw at this point?

Not that this design wasn't inevitably doomed anyway.
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Probably not if it wasn't already damaged. Previous passengers on the Titan reported hearing bangs and snapping sounds. In the case of a normal bathyscaphe or submarine constructed of thick steel, those sounds are caused by buckling or flexing of the hull material under stress. Even very minor buckling can sound very loud, and when the vessel surfaces, those stresses are released and the hull material usually goes back to very close what it was like before. But this is not the case with composites. In the Titan, every one of those was the sound of fibres in the hull fracturing, and when composite fibres fracture, they don't go back to the way they were before. There is also no effective way to repair them, so the damage is cumulative.

Titan had visited Titanic four times before this dive, but had done another nine dives to similar depths. Every one of the fractures in the hull fibres on each dive was a new one. From what I understand of the materials engineering involved in building a cylindrical composite pressure vessel, there is no way to guarantee exactly even density and thickness around the whole structure and this will result in weaker areas and stronger areas, and while fractures are likely to happen mostly in the weaker areas, that is not always guaranteed. If several fractures were to accumulate in a small area, this would drastically weaken that area, so yeah, under those circumstances, a sudden acceleration under pressure might lead to a failure. I recall there was a similar problem on Apollo 10 when they were testing the LM. JayUtah could speak more authoritatively on this than me, but IIRC at one point during the flight, the Grumman head engineer Tom Kelly became concerned when he saw one of the helium tank pressures approaching the upper tolerance limit. He was worried that when the descent engine was fired, the sudden acceleration could cause the pressure inside that tank to spike and lead to it rupturing.

To get a sense of how quickly the Titan implosion happened, the human sensory system requires around 10 milliseconds for the signals from the body's outer sensors to reach the brain, and then the brain takes around 100 milliseconds to "feel" the pain. Titan filled with water and imploded in less than 1 millisecond. The five occupants did not know what hit them, in the truest and most literal sense of the expression.
 
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I remember reading that there were people in the industry who expressed concerns that Rush had a tendency to descend too fast out of impatience.
 
smartcooky said:
Probably not if it wasn't already damaged. Previous passengers on the Titan reported hearing bangs and snapping sounds.
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Last I heard, Rush took a pseudo-evolutionary approach to that, for lack of a better term. He thought that the weak strands of carbon fiber would break, and the good ones would last. How that went for him, well, you already know.

But basically it's not just less fibres with each dive, but water under pressure would get into the cracks, and make more fibres snap.
 
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Scott Manely, who normally does very good YouTubes about space news has just released this one on the Titan submersible.



Edit. Am watching it now. See pictures of the remains. Scott is fascinated by engineering disasters. Great lesson in how things work.
He explains how it failed. It failed at one end, not in the middle as most people thought would happen.
 
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I guess we can also definitively say now that the alleged "transcript" of communications between the submersible and the surface that we saw earlier was in fact fake.
 
rjh01 said:
Scott Manely, who normally does very good YouTubes about space news has just released this one on the Titan submersible.



Edit. Am watching it now. See pictures of the remains. Scott is fascinated by engineering disasters. Great lesson in how things work.
He explains how it failed. It failed at one end, not in the middle as most people thought would happen.
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That depends on how you define "most people". Igf you mean "most people" on the Internet, I'd agree, but if you mean
"most people with some knowledge of structural engineering" I would probably disagree.

A lot of people have said they were concerned about the interface between the titanium ends and the carbon fibre. The pressure on each component would deform it, but because titanium and carbon fibre are different materials, the deformation would be different. If the titanium ring gets smaller (not sure if it is this way round, but it's just an illustration) but the carbon fibre doesn't. That will put enormous stresses on both at the interface which might be out of tolerance.

This is one reason why everybody else makes their deep sea submersibles out of one material (give or take some windows).
 
jeremyp said:
That depends on how you define "most people". Igf you mean "most people" on the Internet, I'd agree, but if you mean
"most people with some knowledge of structural engineering" I would probably disagree.

A lot of people have said they were concerned about the interface between the titanium ends and the carbon fibre. The pressure on each component would deform it, but because titanium and carbon fibre are different materials, the deformation would be different. If the titanium ring gets smaller (not sure if it is this way round, but it's just an illustration) but the carbon fibre doesn't. That will put enormous stresses on both at the interface which might be out of tolerance.
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I'm fairly sure I've heard that very early in that saga, even without being a structural engineer myself. In fact, it's the first time I even hear anyone saying it would be in the middle. Most people who didn't know about it, just didn't assume any particular place where that would happen.

Besides, that's really just relevant for what caused it, rather than where it started. Such a catastrophic failure would pretty much propagate as a shockwave at the speed of sound through the material, which is about 11 KILOMETRES per second along the fibre for carbon fibre and epoxy composite. (Pressure travels at the speed of sound.) Given Titan's size, it would be irreversibly screwed all over in half a millisecond.

Whether that started at one end or in the middle, meh, the latter might make it more like a quarter of a millisecond, but it's kinda splitting hairs at that point :p

jeremyp said:
This is one reason why everybody else makes their deep sea submersibles out of one material (give or take some windows).
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Well, yes, but this thing would have failed anyway, just later.

And their "safety measures" would have been useless anyway, because carbon fibre has no margin between still elastic as usual, and broken. With say, steel, you have a wide band of non-elastic deformation between being pushed too hard and actually breaking. Which you could measure and possibly react to. Carbon fibre doesn't have it. All you can ascertain is that SOME fibres HAVE just snapped. Which Rush had been ignoring all along. But there is very little you can do to ascertain that you're starting to push the whole thing too far towards catastrophic failure, before it actually does fail.
 
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jeremyp said:
That depends on how you define "most people". Igf you mean "most people" on the Internet, I'd agree, but if you mean
"most people with some knowledge of structural engineering" I would probably disagree.

A lot of people have said they were concerned about the interface between the titanium ends and the carbon fibre. The pressure on each component would deform it, but because titanium and carbon fibre are different materials, the deformation would be different. If the titanium ring gets smaller (not sure if it is this way round, but it's just an illustration) but the carbon fibre doesn't. That will put enormous stresses on both at the interface which might be out of tolerance.

This is one reason why everybody else makes their deep sea submersibles out of one material (give or take some windows).
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This. I don't remember what was discussed in the media when, but on this thread we were discussing the material interfaces as a likely issue, right after confirmation of the implosion (page 11).
 
Myriad said:
This. I don't remember what was discussed in the media when, but on this thread we were discussing the material interfaces as a likely issue, right after confirmation of the implosion (page 11).
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Back when the story first broke, my wife, who has her Master's in materials engineering, pointed to that titanium ring being bonded to the composite tube as the most insane part of that design. She was absolutely flabbergasted that they made that interface that way. And she's not one to use expletives often, but when she saw video of them touching the mating surface with bare hands before applying the epoxy by hand, she responded "WHAT THE ****???".
 
Foster Zygote said:
Back when the story first broke, my wife, who has her Master's in materials engineering, pointed to that titanium ring being bonded to the composite tube as the most insane part of that design. She was absolutely flabbergasted that they made that interface that way. And she's not one to use expletives often, but when she saw video of them touching the mating surface with bare hands before applying the epoxy by hand, she responded "WHAT THE ****???".
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Seems that if a professional engineer working for Rush signed off on this design they should be rather worried about retaining their license.
 
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