About the news of missing Titan sub

[Vanadium 50]

A few points, in random order

• It's a submersible, not a submarine.
• There is more to acoustic undersea surveillance than a microphone and a guy with headphones.
• Sound can travel a long way underwater, but there are lots of sounds underwater. It is far from clear that had the mothership been listening they would have known what they are hearing.
• The same properties of water that cause sounds to sometimes carry much greater distances than average also cause sounds to sometimes carry much smaller distances than average also,
• At depth, the water pressure is about 5500 psi. That limits a lot of options.
• Shouldn't this be in GD?
• Major world governments spending a lot of time, money and effort listening to the oceans. They do not want their capabilities in this respect known to their potential future adversaries. So they are cagey about what they do and do not disclose.
• Once there is an implosion it no longer is "rescue". It is now "recovery" and is much less time-critical.

 

[berkeman]

It's a submersible, not a submarine.

I'm too lazy right now to go back to Google. What's the difference, no torpedos?

Shouldn't this be in GD?

Good point; I'll move it now.

 

[DaveC426913]

I had a similar experience although there was no glee.

It troubles me to have to clarify that "giggling with glee" is not surrounded by air quotes; those are bona fide quote marks - as in: I am quoting his words about how he's feeling.

 

[DaveC426913]

I'm too lazy right now to go back to Google. What's the difference, no torpedos?

Submarines are independently operable. They can get to and from their port of call (or whatever) unassisted.

The crew of this submersible can't even exit the craft on their own. They're bolted in. If they had surfaced safely and had been bobbing on the ocean all this time they'd still be dead by now, just inches from life-giving air.

 

[berkeman]

The crew of this submersible can't even exit the craft on their own. They're bolted in. If they had surfaced safely and had been bobbing on the ocean all this time they'd still be dead by now, just inches from life-giving air.

"Yeah, the hatch. We need a hatch with explosive bolts that we can open ourselves."

(Quiz Question -- what movie is that from?)

 

[hutchphd]

(Quiz Question -- what movie is that from?)

Mercury capsule.......Right Stuff?

 

[Slimy0233]

I read most of the comments (especially comments after the time Navy confirmed the implosion), I wonder how the crew might have died. Is it too graphic to ask someone? I mean, I as a puny human can't imagine such great forces. Would they have been compressed? Would they have lose consciousness instantly (painless death let's say)? Also, what would their bodies look like after the implosion?

 

[DaveC426913]

I read most of the comments (especially comments after the time Navy confirmed the implosion), I wonder how the crew might have died. Is it too graphic to ask someone? I mean, I as a puny human can't imagine such great forces. Would they have been compressed? Would they have lose consciousness instantly (painless death let's say)? Also, what would their bodies look like after the implosion?

This may be too graphic to be an appropriate topic of discussion here. I suggest, instead, that you Google Byford Dolphin Disaster to get a pretty good idea. Some articles are more detailed than others. YMMV.

 

[DaveC426913]

"... likely..."

 

[DaveE]

A few points, in random order

• It's a submersible, not a submarine.
• There is more to acoustic undersea surveillance than a microphone and a guy with headphones.
• Sound can travel a long way underwater, but there are lots of sounds underwater. It is far from clear that had the mothership been listening they would have known what they are hearing.
• The same properties of water that cause sounds to sometimes carry much greater distances than average also cause sounds to sometimes carry much smaller distances than average also,
• At depth, the water pressure is about 5500 psi. That limits a lot of options.
• Shouldn't this be in GD?
• Major world governments spending a lot of time, money and effort listening to the oceans. They do not want their capabilities in this respect known to their potential future adversaries. So they are cagey about what they do and do not disclose.
• Once there is an implosion it no longer is "rescue". It is now "recovery" and is much less time-critical.

If I may presume to add a bullet point:

• What the armed forces tell the news media may be very different than what they are saying on the bridge of the command vessel. It looks really bad if you give up to early, OTOH, and extra day or two of searching is both good PR and good training. Plus, they might not be 100% sure, maybe 90% sure isn't good enough.

 

[Baluncore]

OTOH, and extra day or two of searching is both good PR and good training.

It is important that a search be efficient and safe, without unnecessary additional risk. Every action is part of a training exercise, from which lessons will be learned. Log everything.
We are learning;
1. How long it takes to respond to a real submersible emergency.
2. Operational monitoring and communication requirements.
3. Things to avoid when constructing submersible vessels.
4. The applicability of external and independent transponders.

 

[Slimy0233]

View attachment 328281

"... likely..."

There's always a possibility that they were teleported by an alien UFO who foresaw this accident. :')

 

[Baluncore]

Maybe ChatGPT can be sued for not giving sufficient warning.
It had all the information necessary, and failed to act.

 

[Vanadium 50]

What's the difference,

A submarine does not require a support ship - it can execute its mission from pierside to pierside.,

This is a statement about what it can do, not what it does do. A submarine operating wuth the support of a surface shup does not become a submersible. Although I understand that the IAU wants to reclassify thm as "dwarf submarines", starting with the HMS Pluto.

 

[Vanadium 50]

the hatch....explosive bolts

Remember 5500 psi? You have 3 tons per square inch and a could hundred square inches and your "hatch" doesn't look like a hatch any more. It's a thick, semiconical metal plug. I have neither4 seen rgus one or pictures of it, but suspect that it is too heavy for muscle-power to move. It likely requires a special fixture to get it on and off.

Pyrotechnicl fasteners (what the 'pros' call explosive bolts) atr problematic - not only do they not have the necessary oomph. in what direction do they point?

 

[Rive]

in what direction do they point?

It's a frequent topic for 'gun fails' when the barrel is plugged by whatever reason - and suddenly all the oomph coming out on the other direction, yes...

I have neither4 seen rgus one or pictures of it, but suspect that it is too heavy for muscle-power to move.

Well, not really.

I think a more important issue is, that these subs are usually barely able to float so to safely open that can it's better to have it out of the water first.

 

[Vanadium 50]

A submarine that is neutrally buoyant in 4C water at 5500 psi will be negatively buoyant at 15C and 15 psi.

 

[hutchphd]

At depth the "fasteners" are irrelevant. This is in contradistinction to spacecraft (except Apollo block 1). For operations near the surface it is good to have your hatch securely fastened. At the surface it would be nice to be able to somehow extricate yourself although you probably would not wish to remove the entire front of your craft.
The cheapest solution is to bolt the spam into the can. It is a compelling argument.

 

[russ_watters]

I read most of the comments (especially comments after the time Navy confirmed the implosion), I wonder how the crew might have died. Is it too graphic to ask someone? I mean, I as a puny human can't imagine such great forces. Would they have been compressed? Would they have lose consciousness instantly (painless death let's say)? Also, what would their bodies look like after the implosion?

Using the slowest/easiest assumptions I can think of, the sub and everything in it would be obliterated in about 1/120th of a second. That's how long it would take for the window to traverse the length of the sub if smoothly accelerated up to the speed of sound (of water). Way too fast for human perception. But it likely collapsed from the sides, not the front and back. It's not unlike standing next to an explosion.

I also calculate the energy to be 32 kg of tnt, which unlike an explosion, all of it is directed towards the occupants.

 

[russ_watters]

At depth the "fasteners" are irrelevant. This is in contradistinction to spacecraft (except Apollo block 1). For operations near the surface it is good to have your hatch securely fastened. At the surface it would be nice to be able to somehow extricate yourself although you probably would not wish to remove the entire front of your craft.
The cheapest solution is to bolt the spam into the can. It is a compelling argument.

Looking at the DSV Alvin, it had a hatch on top, held in place by its weight and water pressure. It's unclear to me though if it can be opened from inside due to the weight.

But the Titan seems to have been more cheaply/simply engineered..

 

[Astronuc]

But it likely collapsed from the sides, not the front and back. It's not unlike standing next to an explosion.

If the personnel chamber is tubular/cylindrical rather than spherical, it would be much more prone to buckling, which I suspect is the mechanism of failure. Any amount of eccentricity, lack of concentricity, or nonuniformity in wall thickness increases risk.

Alvin and Trieste used spherical personnel chambers.
https://en.wikipedia.org/wiki/DSV_Alvin
https://en.wikipedia.org/wiki/Trieste_(bathyscaphe)
https://en.wikipedia.org/wiki/Trieste_II_(Bathyscaphe)

So it can be done right as evidenced by the visits to 20,000 ft (6096 m) depth down to 10,911 metres (35,797 ft) in the Challenger Deep of the Mariana Trench near Guam.

As I understand the news, the Titan may have imploded at around 9000 ft (2743 m), so it didn't even get to the Titanic depth. It suggests severe design deficiencies. The lack of certification is troubling. The reason for having regulations (mandatory rules in design and construction, followed by rigorous testing) and following them is precisely to prevent such tragedies.

 

[Vanadium 50]

obliterated in about 1/120th of a second.

And in that time the sound of the implosion would have traveled around 40 feet. So "why didn't the sonar operators do something?" has an easy answer - by the time the sound made it to them, there was nothing to be done.

 

[JLowe]

As I understand the news, the Titan may have imploded at around 9000 ft (2743 m), so it didn't even get to the Titanic depth. It suggests severe design deficiencies. The lack of certification is troubling. The reason for having regulations (mandatory rules in design and con

There aren't enough regulations in the world to persuade me to ride a private sub to 13k feet. It's hard to believe billionaires weren't aware of the risk regardless of what was claimed. I have sympathy, but this isn't something to be doing on a whim with a "trust me bro" CEO.

 

[Vanadium 50]

And if you ban this, do you also ban space tourism? Mountain climbing? (Who certifies those Sherpas anyway?) Swimming in the ocean? Eating fugu? Eating a high-cholesterol steak dinner? Anything that follows the phrase "Hey, hold my beer."? Where do you draw the line?

 

[BillTre]

There aren't enough regulations in the world to persuade me to ride a private sub to 13k feet. It's hard to believe billionaires weren't aware of the risk regardless of what was claimed. I have sympathy, but this isn't something to be doing on a whim with a "trust me bro" CEO.

I would seriously consider going in James Cameron's sub.

 

[russ_watters]

[note regarding now deleted post]
Let's not get disrespectful of the dead please.

 

[Astronuc]

Nice little map in this article
https://www.yahoo.com/news/titanic-who-pay-attempted-sub-rescue-130025604.html

 

[Vanadium 50]

But the Titan seems to have been more cheaply/simply engineered..

If you mean that they don't have the resources of a major world government behind them? I agree. But the same can be said of SpaceX - who also advocates simplicity.

If we are to play Monday Morning Quarterback, the two things that concern me are the diving to 98% of the maximum depth - no margin there - and the lack of adequate testing for ctclic fatigue.

There are standards for commerical pressure vessels, and I expect no submersible anywhere meets them. It would maken it far too heavy, and likely useless for observation. But prudence suggetss you get as close as you can.

 

[DaveC426913]

[James] Cameron told ABC News that he believes the Titan's hull began to crack under pressure and that its inside sensors gave the passengers a warning to that effect.

"We understand from inside the community that they had dropped their ascent weights and they were coming up, trying to manage an emergency," he said.

https://www.npr.org/2023/06/23/1183975136/james-cameron-titanic-titan-sub

 

[Vanadium 50]

If you mean an honest-to-goodness crack, these failures are very fast. One area can no longer support the load, so it is transferred to nearby areas, which can no longer support the now-lareger load, so the crack grows, and so on and so on.

If you mean metal fatique, of which microcracks are an important part, I agree. It's easy to imagine a network of strain gauges and this network repoting something not right. The problem as I see it is a pressure of 40 MPa and a tensile strength of 200 MPa or so for titanium means any unbalanced force is very dangerous. If the response - e.g. creep - makes things even more unbalanced, things go very bad very quickly.

 

[Baluncore]

That Titan had dived to full depth before, and now failed many percent short of that previous proof depth, suggests that the cyclic ageing of the hull, was occurring at a rate of many percent, per dive cycle.

A cylindrical carbon fibre body would work well as an internal pressure vessel. There, pressure is countered by tension in the carbon fibres, while the polymer, held in place by tense fibres, would block the holes between the fibres.

Under high external pressure, tension would be removed from the fibres, the polymer filler would be progressively crushed without the fibres holding it in place. Each cycle of crush would damage more polymer, and so reduce the safe depth, until it failed before reaching the operating depth. Ultimately, one side of the cylinder would buckle inwards, inverting that side of the cylindrical pressure vessel wall.

I cannot see any advantage gain, from including tensile carbon fibre in the construction of vessels subject to high external hydrostatic pressure.
Maybe there is something about that construction, that I do not understand. Any ideas?

 

[Astronuc]

I was listening to an interview on NPR's All Things Considered and Mary Louise Kelly said the following.

KELLY: What has gone through your mind this week as details have emerged, such as that the Titan was built to withstand a certified pressure of 1,300 meters? The Titanic shipwreck that it was going to look at lies nearly 4,000 meters below sea level.

I'm not sure of the origin/source of this information, and I have not heard it before. As I understand it, OceanGate's Titan submersible is NOT certified. Perhaps the hull manufacturer assured some depth or external pressure, perhaps 1300 m. If that's the case, but OceanGate was diving to 4000 m, that would seem grossly negligent. I imagine the wall thickness was insufficient.

Meanwhile, an AP News article discusses the design.

The Titan, owned and operated by OceanGate Expeditions, first began taking people to the Titanic in 2021. It was touted for a roomier cylinder-shaped cabin made of a carbon-fiber — a departure from the sphere-shaped cabins made of titanium used by most submersibles.

The sphere is “the perfect shape,” because water pressure is exerted equally on all areas, said Chris Roman, a professor at the University of Rhode Island’s Graduate School of Oceanography. Roman had not been on the Titan but has made several deep dives in Alvin, a submersible operated by the Woods Hole Oceanographic Institute in Massachusetts.
https://apnews.com/article/titan-titanic-submersible-design-49b8c2a713f316ce5987a394a27d23e8
The 22-foot long (6.7-meter long), 23,000-pound (10,432-kilogram) Titan’s larger internal volume — while still cramped with a maximum of five seated people — meant it was subjected to more external pressure.

Furthermore, the Titan’s 5-inch thick (12.7 centimeters) hull had been subjected to repeated stress over the course of about two dozen previous dives, Graham-Jones said.

Each trip would put tiny cracks in the structure. “This might be small and undetectable to start but would soon become critical and produce rapid and uncontrollable growth,” he said.

 

[256bits]

From post 67 @Astranut
Each trip would put tiny cracks in the structure. “This might be small and undetectable to start but would soon become critical and produce rapid and uncontrollable growth,” he said.

and those cracks should be able to be seen after each dive with a check on the submersible structure through non-destructable testing.

Now since this is a submersible with a composite body, has enough evidence over the years been collected to fully guage how safe a craft of this type would be after each dive. Are the analysists capable of of fully appreciating the test results?

From post 66 @Baluncore,
With the pressure reduced after coming back to the surface, I would expect there to be micro voids and separation within the hull body composite material, along with micro fiber breakage upon relaxation ( or rather return to tensile stresses among the fiber material itself ).
It would seem to me that the fatigue life of a composite hull subjected to these compression stresses to be rather lower than a hull constructed from metallic material.

 

[russ_watters]

If you mean that they don't have the resources of a major world government behind them? I agree. But the same can be said of SpaceX - who also advocates simplicity.

The fist trip is always the hardest. Most of the engineering was already been done for this problem 50 years ago and they ignored it.

Monday Morning Quarterback, the two things that concern me are the diving to 98% of the maximum depth - no margin there - and the lack of adequate testing for ctclic fatigue.

Maybe cheap is the wrong criticism. It's that they ignored basic engineering principles.

 

[256bits]

I cannot see any advantage gain, from including tensile carbon fibre in the construction of vessels subject to high external hydrostatic pressure.
Maybe there is something about that construction, that I do not understand. Any ideas?

Roomer compartment
Less weight for the craft
Support vessel and components of lessor size, and perhaps manpower.

Conclusion:
Design criteria --> as always, $ providing the impetus.( so that is not a negative assessment on its own )

Note that all designs follow the $ criteria, except for experimental, where budgets can be exceeded very quickly. Rules, regulations, and certifications are design guidelines from where to start for new concepts.

The craft, being accused of being not certified, is probably a red-herring. The guy is/was correct in stating that rules and regulations hinder innovation - no design engineer is going to argue the incorrectness of his viewpoint, as that is what engineers do - provide new designs at the frontier of technology ( example - bridges would still be of the same design of solid rock from the Roman empire, and steel would not have had its hay-day )

If anything, if one does want a certification label, that would have been " EXPERIMENTAL".
In time a new class would have come into existence.

Beebe and his diving ball was a first of its kind for deep sea exploration.
https://en.wikipedia.org/wiki/Bathysphere