Technical Analysis on Titan Sub (Titanic Sub)

[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

 

[Baluncore]

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

Roomier?
How do tensile fibres help when they are under compression?
Carbon fibre is not always good.

 

[256bits]

a look at some of the regs for these present types of vessels.
https://ww2.eagle.org/content/dam/e...yperbaricfacilities_2021/uwvs-rules-jan21.pdf

Roomier?
How do tensile fibres help when they are under compression?
Carbon fibre is not always good.

Make a heavy craft with a volume inside.

Make the a craft with a less dense material.
a a general rule:Two choices.
One can either have the same outside dimensions and thus a similar inside volume.
Or a craft of the same weight, with larger outside dimension, and thus more room inside.

The automobile industry has been doing this for years, so not a surprise.
Ships - same thing.
Would you rather lug around a 14 foot pleasure boat made out of steel, or one made out of composite.

 

[Baluncore]

The automobile industry has been doing this for years, so not a surprise.
Ships - same thing.
Would you rather lug around a 14 foot pleasure boat made out of steel, or one made out of composite.

THOSE ARE NOT EXTERNAL PRESSURE VESSELS.
YOU ARE MISSING THE POINT ENTIRELY.

 

[256bits]

THOSE ARE NOT EXTERNAL PRESSURE VESSELS.
YOU ARE MISSING THE POINT ENTIRELY.

What??
Design and manufacture of better and improved products is missing the point.
The point of what sir?

 

[Baluncore]

The point of what sir?

A high external pressure causes the vessel to become 1% smaller, so the carbon fibres are no longer under tension, therefore the carbon fibres are not an advantage.

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.

 

[Astronuc]

a look at some of the regs for these present types of vessels.
https://ww2.eagle.org/content/dam/e...yperbaricfacilities_2021/uwvs-rules-jan21.pdf

Carbon composites are not explicitly mentioned, but fiber reinforced structures are handled on a case-by-case basis.

There are technical requirements:
7.1.3 Structural Members in Axial Tension or Compression
7.1.4 Structural Members in Bending
7.1.5 Structural Members Subject to Shear
7.1.6 Structural Members Subject to Combined Axial Compression and Bending
7.1.11 Structural Members Subject to Buckling
It would seem these basic (based on extensive experience) design requirements were ignored.

The extraordinary combination of the lightweight and high strength properties of carbon fibres and their composites makes it an ideal for many existing and emerging applications in weight sensitive industries from aerospace, sports and leisure, defence, automotive to wind energy. However, the inferior longitudinal compressive performance of carbon fibres and their composites compared to their tensile properties limits their wider usage. Indeed, the compressive strength of carbon fibre and carbon fibre composites are about 30 to 50 % of their tensile strength. As will be discussed, the knockdown in properties is controlled primarily by the microstructure of the fibre, while for the composite, compression is sensitive to manufacturing methods, laminate design, voids and other process induced defects. This limitation in compression has therefore led to design constraints that prevent structural components from taking full advantage of the highly desirable properties of carbon fibre.

A review of the structural factors which control compression in carbon fibres and their composites​

https://www.sciencedirect.com/science/article/pii/S026382232201025X

Five lives is a high price to pay for failing to do one's homework (basic calculations and testing). Certification is done by experts - with experience, or at least it should be.

The fate of Titan was avoidable/preventable.

Design requirements are based on physical/technical limits of materials (set by Nature), which establish real design constraints. We often design with safety factors to ensure under operating conditions that applied stresses do not approach, and certainly do not exceed, stress capabilities (strength) of the materials.

A forensic investigation into the design process at OceanGate is needed in order to understand the design deficiencies.

Rules and regulations do not inhibit innovation, but rather they are there to ensure safety (i.e., prevent/preclude injury or death).

From a Scientific American article:

“We found five different major pieces of debris that told us that it was the remains of the Titan,” said Paul Hankins, director of salvage operations and ocean engineering at the U.S. Navy, during the press briefing. The searchers’ initial find was the nose cone, followed by a large debris field, where they discovered the front end of the pressure hull. “That was the first indication there was a catastrophic event,” Hankins said. In another span of debris, a smaller one, they found the other end of the pressure hull, which “basically comprised the totality of the pressure vessel.”

https://www.scientificamerican.com/article/what-we-know-about-missing-titanic-tourist-sub11/

So, it would appear the pressure chamber was crushed laterally (radially) and did not telescope. The implosion blew apart the nose cone and front end of the hull and the back end of the hull.

 

[Vanadium 50]

I cannot see any advantage gain, from including tensile carbon fibre in the construction of vessels subject to high external hydrostatic pressure.

Weight. You want your vessel to have about the same density as water. Too much less and it doesn't go down. Too much more and it doesn't come up.

Related is size. Economics says room for N ticket-holders is better than N-1. And the economics is marginal: they seem to be averaging sales around $3M a year, somewhat better than an average McDonalds, and from that pay for the staffm a very expensive vessel, rental of a very expensive support vessel and everything else.

My experience with carbon fiber - whuch is not with submersibles - is that it's pretty amazing stuff. However, transitions to conventional materials are difficult. That's where the problems end up.

It's that they ignored basic engineering principles.

Which one did you have in mind?

Rules and regulations do not inhibit innovation, but rather they are there to ensure safety (i.e., prevent/preclude injury or death).

I don't believe diving to the Titanic can be done safely - and I am defining "safely" as a 99% survival rate. There seem to have been about fiftyh manned dives, and one faiure.

Should we as a society say that this means that nobody can do it?

As far as certification, who certifies? This is not some sort of glorified glass-bottomed boat. There are about a dozen of such vessels in operation, with a good number being operated by countries with frosty relations with the West,

There is also the question of who has authority. The dive took place in international waters.

 

[Rive]

Weight

He means, ropes (fibers) are great for pulling but not so great for pushing.
External pressure is expected to make the vessel shrink, not expand.

 

[Baluncore]

So, it would appear the pressure chamber was crushed laterally (radially) and did not telescope.

That is expected, since a cylinder with a pressure difference is subjected to a hoop stress that is twice the axial stress. A cylindrical structure would only concertina length-ways if it had circular bulkheads and ribs, holding the cylindrical pressure hull in place radially. Those ribs would double the depth it could dive, but if it lost control of depth and dived further, it would then concertina. I believe the Thresher suffered a concertina implosion that significantly reduced the length of the submarine.

 

[Vanadium 50]

External pressure is expected to make the vessel shrink, not expand.

Ah, but you aren't trying to keep the hull from shrinking. You're trying to keep it from buckling. (Which has tension on one side and compression on the other)

 

[Baluncore]

You're trying to keep it from buckling.

The hoop compression removes all tension from the fibres, both at the inside radius and outer radius. It would require a significant deflection before the fibre was again taut. Since deflection leads to a local increase in stress, that initial allowed deflection is best avoided.

The hoop compression occurs across the whole section. It is the polymer fill that is subjected to, and must resist, the hoop compression.

 

[Astronuc]

As far as certification, who certifies?

U. S. Naval Sea Systems Command (NAVSEA), or equivalent. At least, OceanGate designers should be using the appropriate design methodology based on proven materials.

There is also the question of who has authority. The dive took place in international waters.

OceanGate is based in US.

March 10, 2015

The Woods Hole Oceanographic Institution (WHOI) announces that the Human Occupied Vehicle (HOV) Alvin has achieved certification from the U. S. Naval Sea Systems Command (NAVSEA) for operations to its rated depth of 4,500 meters (approx. 2.8 miles). Two certification dives were conducted in the waters off Arica, Chile, on January 26-27 from the research vessel Atlantis, to demonstrate vehicle performance. Navy representatives were on hand to monitor the process and participate in the dives.

Certification of Alvin to 4,500 meters represents the successful culmination of the $41-million, multi-year upgrade of the submersible funded by the National Science Foundation with a significant cost share by WHOI. In January 2014, NAVSEA certified Alvin to a depth of 3,800 meters, clearing the vehicle to return to service. In March 2014 a group of scientists put Alvin through its paces in the Gulf of Mexico, test-driving the upgraded vehicle and its new sampling, imaging, surveying and navigation systems. Alvin has subsequently made 99 dives during missions to the Gulf of Mexico, Juan de Fuca Ridge, and East Pacific Rise. Alvin was positioned in early 2015 off Chile, where depths of 4,500 meters were readily available to complete the certification trials to its full design depth.

https://www.whoi.edu/press-room/news-release/alvin-4500m/

In July 2022

World’s most successful research submersible reaches 6,453 meters, its deepest dive ever​

Woods Hole, MA — Today, the human-occupied submersible Alvin made history when it successfully reached a depth of 6,453 meters (nearly 4 miles) in the Puerto Rico Trench, north of San Juan, P.R. This is the deepest dive ever in the 58-year history of the storied submersible.

The dive was a critical step in the process of achieving certification from the U.S. Navy to resume operations after an 18-month overhaul and upgrade that extended the sub’s maximum dive rating from 4,500 meters (14,800 feet) to its new limit of 6,500 meters (21,325 feet). Naval Sea Systems Command (NAVSEA) requirements stipulate the certification dive be between 6,200 and 6,500 meters.

The three-person crew aboard Alvin for this history-making dive were: Anthony Tarantino (Woods Hole Oceanographic Institution (WHOI), pilot); Fran Elder (WHOI, mechanical engineer); and Mike Yankaskas (NAVSEA).

https://www.whoi.edu/press-room/news-release/human-occupied-submersible-alvin-makes-historic-dive/

In 2011-2012, upgrades to Alvin

2011 - 2012​

During this two-year period Alvin was completely disassembled and upgraded with several notable improvements, including:

• A new, larger titanium personnel sphere with an ergonomic interior designed to improve comfort on long dives
• Five viewports (instead of the former three) to improve visibility and provide overlapping fields of view for the pilot and two observers
• New lighting and high-definition imaging systems
• New syntactic foam for buoyancy
• An improved command and control system

The personnel sphere was forged from titanium ingots in Wisconsin, machined and welded in California, heat treated in Ohio, pressure tested in Maryland and underwent final assembly in Texas before being shipped to Woods Hole. It is an inch thicker than the previous sphere, and has 27 cubic feet more interior volume. Alvin's titanium frame was modified in New Jersey to accept the new sphere, and new syntactic foam was manufactured and installed to float the increased submersible weight. All thrusters are now releasable in the event of entanglement, as are the manipulators, batteries and science workspace platform. High definition cameras and LED lights have been added, and fiberoptic cables transmit high quality video signals to recorders within the sphere.

https://www.whoi.edu/what-we-do/explore/underwater-vehicles/hov-alvin/history-of-alvin/

Final assembly of the submersible continued into the early months of 2013. Most of our efforts in late winter and early spring were concentrated on obtaining certification of vehicle subsytems from the Navy's Naval Sea Systems Command (NAVSEA), our certifying authority. Several subsystems, notably life support, received extra scrutiny from NAVSEA engineers due to their critical importance, which delayed approval.

2015​

The submersible operating year began in late January with five qualifying dives off Arica, Chile to officially extend Alvin’s depth rating to 4,500 meters. NAVSEA auditors accompanied the operations team as dives to successively deeper points demonstrated submersible capabilities and readiness for full certification.

2017

The final submersible dives of the season were five engineering descents during the transit from Puntarenas, Costa Rica to Woods Hole, one to our test depth of 4,500 meters. Alvin passed a US Navy functional audit and certification survey in August, and began a seven-month open period shortly thereafter.

2021

The first cruise was a transit to Bermuda for post-overhaul testing, departing Woods Hole October 25. Naval Sea Systems personnel were on board to witness certification activities and approve documentation as the submersible progressed toward 6,500 meter authorization. Following arrival at St. Georges, harbor trials commenced including inclining experiments to ensure adherence to stability standards. Next a series of progressively deeper dives were performed in the vicinity of the island before the ship and sub transited south to deeper water in the Puerto Rico Trench. Alvin made two dives in the Trench, to 3,550 and 5,338 meters, the last being the deepest dive made to date. Unfortunately that dive would be the last of the year as damage to the syntactic foam flotation was discovered after the sub surfaced. It was determined that disassembly of the vehicle would be required to properly address the repair requirements, so Atlantis was rerouted back to Woods Hole in late November so Alvin could be returned to the shoreside hangar. Buoyancy restitution and modification of the frame mounting arrangement is expected to take six months, with a projected return to service in June 2022.

2022

The first cruise departing Woods Hole July 5 bound for San Juan, Puerto Rico facilitated continuation of submersible sea trials begun in 2021. Progressively deeper dives were undertaken in the vicinity of the New England Seamounts and in the Puerto Rico Trench, culminating in certification of the submersible to our new maximum depth rating of 6,500 meters during Dive 5,086 on July 21.

The next voyage, which left San Juan in late July, was a science verification cruise to test operation of ALVIN’s suite of scientific sampling tools. This trip took the ship and submersible north to Tampa, Florida, with dive sites in the Puerto Rico Trench and Cayman Trough. Numerous investigators were aboard to put the upgraded submersible capabilities through rigorous testing. Several more dives in excess of 6,000 meters were accomplished during this series.

Clearly, deep sea diving can be done safely, if done right. It can be expensive.

On the other hand, it can be done cheaply and recklessly, with the result of catastrophic failure. One or more persons decided not to take the risk. I wonder what they knew as opposed to what the four passengers knew. Perhaps the passengers assumed that if the CEO was onboard, it must be safe. Perhaps the risk was minimized or trivialized. Rush was telling the public how safe the industry is. If however, he was including submersibles like Alvin, or if he was including dives at shallower depths, his claims would be misleading at the least.

Should we as a society say that this means that nobody can do it?

Risk is a personal decision. If one wants to risks one's life, one is allowed. It's a different matter of risking others' lives.

I suspect that the fatigue (due to overloading) decreased the crush depth, or diminished the failure threshold, and each successive dive moved closer to the failure limit.

I have to wonder if the craft had a Ti (alloy) bulkhead in the middle of the craft, would it have bought some extra margin.

I've done buckling calculations for thin-walled (0.022 inch (0.560 mm), and thinner) tubes under relatively high pressure loadings. No collapse on more than 10k stainless tubes in service. Stainless steel is more resilient that Zr-alloys, which have half the stiffness as 304/316 SS. Although millions of fuel rods (in PWRs) have operated successfully (they didn't fail) with Zr-alloy cladding, some have collapsed because of excess eccentricity/ovality or other anomalies.

Alvin Dive Statistics
https://www.whoi.edu/what-we-do/explore/underwater-vehicles/hov-alvin/dive-statistics/

I was hoping to find how many dives they have performed at 4000 m and deeper.

 

[hutchphd]

As far as certification, who certifies? This is not some sort of glorified glass-bottomed boat. There are about a dozen of such vessels in operation, with a good number being operated by countries with frosty relations with the West,

There is also the question of who has authority. The dive took place in international waters.

Risk is a personal decision. If one wants to risks one's life, one is allowed. It's a different matter of risking others' lives.

I think this is the crux here. The passengers in the sub were technically trained people capable of decision (maybe not the 19 yr old?). The availability (or lack) of any competent certification would heavilly weigh upon me putting my soft pink flesh inside that tank . I think Darwin is, on the whole, better than regulation for truly personal decisions.

That being said I believe that any expectaton of extraordinary emergency response should be predicated upon some robust and sufficient pre-certification, and that should be a societal norm. If you want to just hang your hindquarters way over the edge then go for it, but don't expect me to help pay the piper.

And how many bodies are adrift in the Mediterranean today?

 

[Vanadium 50]

NAVSEA? That's really bizarre. It;s not like the Air Force certifies what United Airlines flies. My only thinking is that Alvin undertakes...um..may undertake naval operations.

And why the US? The trip starts and ends in Canada and the dive is in international waters.

To be honest, I don't think we know if this was a gradual fatigue (my guess too, BTW) or some damage on the last ascent, or even damage done during inspection.

ASME has standards for pressure vessels. I haven't looked at them in this context, but I am fairly certain that had they been followed, the vessel would be too heavy to surface, Which is not good either.

That's also what got me thinking about jurisdiction. Getting a US-approved pressure vessel approved to operate in Europe, or vice versa, is a pai - an expensive pain - even though the standards are very similar.

I have to wonder if the craft had a Ti (alloy) bulkhead in the middle of the craft, would it have bought some extra margin.

As I said, I think the 2% margin was risky. But if they went with titanium rather than HY-series steels, they have a weight problem. And if they have a weight problem they aren't going to be adding this and that. It's also maybe even worth considering that if they had the ability to add more weight they would have been better off making the pressure hull thicker.

 

[Vanadium 50]

If you want to just hang your hindquarters way over the edge then go for it, but don't expect me to help pay the piper.

Thing is, society has already decided at some level. I have some sympathy for your position, don't get me wrong, but that decision has been made:

When people go out for a hike hoping to beat the snowstorm, which is earlier and more severe than forecast, we still send out the St. Bernards to rescue them. (Happened to a friend of mine. Yes it was stupid, but does she need to die from that? And no, they weren't actual St. Bernards)

When a drunk driver hits a tree, the ambulance takes them to the ER. They don't just smell his breath and say, "Whew! OK, buddy, the hospital is about 4 miles thataway. Sorry about the two broken legs, and good luck!"

And so on.

 

[hutchphd]

"Whew! OK, buddy, the hospital is about 4 miles thataway. Sorry about the two broken legs, and good luck!"

I mostly agree that most such decisions have been made, but not all. For instance, there was some talk early in the COVID, with facilities maxed out, to give priority to vaccinated patients (I don't know if this actually occured....and we may not know). Fire and storm victims are routinely warned that calls will not engender response after a certain time so you are on your own.
I don't think we should prohibit customary care to victims in ordinary circumstances, regardless of their idiocy. But likely these decisions will be more and more driven by unacceptable cost rather than technologoical impossibility as scarcity becomes a bigger driver for us on our overburdened planet. And god help me I do occasionally want to dust off my Darwin cap......

 

[DaveE]

As far as certification, who certifies?

The coast guard, I think. They can, and have, stopped vessels from leaving port on a "manifestly unsafe voyage".

https://www.law.cornell.edu/cfr/text/33/177.07

PS: Maybe this is more enforcement than certification though.

 

[JT Smith]

I also agree that people should have some degree of freedom to take what many/most others consider irresponsible risks. At some point there is a societal cost to consider but short of that it should be okay in a free society to risk your life.

But in this particular case there is some suggestion in the media that OceanGate may have been deceptive and perhaps outright lied about some aspects of their product. Even intelligent, technical people can't be expected to have expertise and sound judgement in all things technical. There is a line between risk taking adventurer and duped paying customer.

 

[Astronuc]

CNN - Authorities in Canada and the US each announced the launch of investigations Friday into the implosion of the Titanic-bound submersible that killed all five passengers.

It is unclear whether the probes by the Transportation Safety Board of Canada and US Coast Guard would be one single investigation or two separate, simultaneous examinations. The US National Transportation Safety Board will assist the Coast Guard, the agency tweeted.

The announcements came as investigators continued to scour the ocean floor for any insight into the “catastrophic implosion” on the Titan submersible that suddenly lost communication with its mother ship, Polar Prince, last weekend, officials said.

https://www.cnn.com/2023/06/23/us/submersible-titanic-implosion-deaths-friday/index.html

 

[Vanadium 50]

The coast guard, I think.

Whose coast guard? The dive is in international waters.

And if the US imposes restrictions and high fees, they can just register elsewhere. Why do you see so many Liberian-registered commercial vessels? (And Moldova and Switzerland!)

There is a line between risk taking adventurer and duped paying customer.

Well, one way to prevent this is to have the CEO of the company travel with the customers and...oh wait.

 

[DaveE]

And if the US imposes restrictions and high fees, they can just register elsewhere.

True. But western governments and regulatory agencies can have an outsized effect in the perception of quality/safety, and perhaps the funding for this sort of thing. Of course we can't control what the Somalis do, but that doesn't mean we can't or shouldn't try.

Liberian registered ships still have to be allowed to enter Western ports. Some of that "flag shopping" is about regulations (mostly "red tape"), but much of it is really about taxes.

 

[Astronuc]

Apparently Paul-Henri Nargeolet (77), a former French Navy commander, diver, submersible pilot, . . . had 35 dives to the Titanic site (Wikipedia article).
https://en.wikipedia.org/wiki/2023_Titan_submersible_incident#Fatalities

James Cameron has visited the Titanic site 33 times.
https://www.npr.org/2023/06/23/1183975136/james-cameron-titanic-titan-sub

Cameron "also dove the Mariana Trench — the deepest-known point on Earth, about three times deeper than the Titanic wreck site — in 2012, in a 24-foot cylindrical submersible he spent seven years building." I'm guessing it wasn't carbon fiber composite.

The personnel/pilot capsule was a spherical structure.
https://en.wikipedia.org/wiki/Deepsea_Challenger

Cameron and many others in the deep submergence community had long been concerned about the vessel's safety and OceanGate's experimental approach, he said on Thursday, lamenting that the company had ignored experts' calls to undergo a standard certification process.

I'd like to know more about the 'standard' certification process, which apparently OceanGate ignored.

It's clear that OceanGate "shouldn't have been doing what it was doing," he told Reuters, adding that he had declined an invitation from CEO Stockton Rush to go diving with them this season.

Cameron described OceanGate's use of a carbon-fiber hull as "fundamentally flawed" and said he had warned another company several years ago against using that same design principle. He said he regrets not speaking up more this time around.

https://en.wikipedia.org/wiki/2023_Titan_submersible_incident#Safety

Because Titan operated in international waters and did not carry passengers from a port, it was not subject to safety regulations. The vessel was not certified as seaworthy by any regulatory agency or third-party organization. . . . A 2019 article published in Smithsonian magazine referred to Rush as a "daredevil inventor". In the article, Rush is described as having said the U.S. Passenger Vessel Safety Act of 1993 "needlessly prioritized passenger safety over commercial innovation".

The Challenger Deep mission for DeepFlight Challenger was scrapped after Virgin discovered it was worthy of only a single dive, not the repeated missions planned.
https://en.wikipedia.org/wiki/Deepsea_Challenger#Similar_efforts

OceanGate promoted the Titan’s carbon fiber construction — with titanium endcaps — as “lighter in weight and more efficient to mobilize than other deep diving submersibles” on its website. It also said the vessel was designed to dive four kilometers (2.4 miles) “with a comfortable safety margin,” according to court documents.

https://www.pbs.org/newshour/nation...onal-design-may-have-destined-it-for-disaster

If Rush claimed Titan was designed to 4000 m, or whatever, it was probably a misleading or apotentially false statement, given the lack of design review and certification; I have to wonder if the designers adhered to any standards. I'd like to see the buckling analysis and stress analysis on the CFC. Does it account for the reduction of structural capability with each dive?

Edit/upate:
A prospective Titan passenger said of Rush,

“He basically told me he knew I'm a helicopter pilot, and he said, 'This is safer than flying a helicopter. It's safer than scuba diving.' And at lunch he said, 'It's safer than crossing the street,' " Jay recounts. "He was a good guy, great heart, really believed in what he was doing and saying. But he didn't want to hear anything that conflicted with his world view, and he would just dismiss it.”

“He absolutely believed what he was saying," he continues. "But I didn't want to get into the safety concerns anymore, because he was so vested in his position. And anybody who questioned it just had a differing opinion."

https://www.yahoo.com/entertainment/titan-family-tragedy-averted-due-201531030.html
We don't do proper engineering and science on 'belief'. We need hard objective evidence based on experience and due diligence.

 

[gmax137]

There are international safety standards for passenger-carrying ships, things like how many lifeboats are required, that ironically were put into place following the sinking of the Titanic. SOLAS hes evolved to include design requirements and ongoing inspections (see https://en.wikipedia.org/wiki/SOLAS_Convention).

This is entirely different from something like Cameron's Deep Sea Challenger, a vessel he had built and dove in by himself.

 

[Baluncore]

There are international safety standards for passenger-carrying ships, ...

Titan did not carry passengers.
The "mission specialists" made donations to support the company.

 

[gmax137]

Titan did not carry passengers.
The "mission specialists" made donations to support the company.

Is that really the stance being taken? I hope not, that's shameful.

 

[DaveC426913]

You want your vessel to have about the same density as water. Too much less and it doesn't go down. Too much more and it doesn't come up.

You design the pressure vessel to be as light as practical, so it wants to rise to safety naturally. Then you neutralize the buoyancy with detachible weights on its superstructure.
.

 

[Baluncore]

Is that really the stance being taken? I hope not, that's shameful.

Customers who travelled to the Titanic with OceanGate, referred to as "mission specialists" by the company,[37] paid US$250,000 each for the eight-day expedition.[33][38][39]

https://en.wikipedia.org/wiki/2023_Titan_submersible_incident#Expeditions_to_the_Titanic

 

[gmax137]

That Wiki page is inconsistent. Just above the line you quoted it says:

Titan made its first dive to the Titanic in July 2021. In total, OceanGate undertook six dives to the Titanic in 2021 and seven in 2022. ... Each dive typically had a pilot, a guide and three paying passengers on board.

emphasis added

And following:

Because Titan operated in international waters and did not carry passengers from a port, it was not subject to safety regulations.

Is that a valid legal argument? Sounds kind of murky.

 

[Astronuc]

Is that a valid legal argument? Sounds kind of murky.

I presume the support ship carried the passengers (mission specialists). Then they were transferred in international waters. I suppose they will try that technicality.

 

[Frabjous]

The dead undoubtedly signed safety waivers. A lawsuit would need to prove negligence in order to invalidate them.