UKC

and Brit on Lost Sub To Titanic 

and UK Billionaire Trapped Inside Titanic Tourist Submarine With Air Running Out

Not to mention the 500 people (sorry, migrants) at the bottom of the Mediterranean. 

Call James Cameron.  He knows the area and I think he has a submarine.  More importantly, there must be a movie in this. 

Some interesting bits around this story -  a US reporter who travelled on it recently said that they lost comms with the support vessel on their trip. He also said the sub was driven using a games console controller (?) and the lighting seemed to be from a camping shop. Probably both a bit harsh criticisms, but still - doesn't sound like something James Cameron or Jeff Bezos would get in.

Looking at Action Aviation website - it seems Hamish is addicted to extreme adventures with a decent tick list of mariana trench/south pole/space flight etc...

Hopefully all come back safely, but can't imagine it it will be easy to recover the vessel if it's trapped in Titanic wreckage.

EDIT - yes it is a games controller https://www.youtube.com/watch?v=ClkytJa0ghc&t=164s

Everything about that sub looks like a cobbled together in the garden shed job, even the lifting strap is a sling tied on with a bit of polyprop rope. All supported by a 64 year old ship.

at $250000 per person for a trip, I'm in the wrong business

Haven't really been following it and don't know much about the sub in question, but aside from a few military exceptions Deep Submergence Vessels (DSVs) typically have a pretty short endurance. Getting another DSV to the area to perform a rescue will probably take a while; you could probably get a small one on a C5 Galaxy or antonov and fly it to somewhere close, but you'd need a surface support vessel to operate it. Hopefully they have a supply of chlorate candles or some similar oxygen reserve, co2 scrubbers and some way to stave off hypothermia, plus the search area will be fairly small which helps their chances.

Of course there may have been some sort of catastrophic failure. Most DSVs I think have a sealed pressure sphere without quite the myriad of pipework and other equipment that military subs have passing in and out of it, which would reduce the chances of taking in water. Implosion is pretty much unheard of within the design depth, though I guess not completely impossible. In the thankfully small number of instances of implosion the sound has been picked up by military hydrophone networks so we'd have probably heard by now if that had happened.

I don't see this as a big deal. Its an off the shelf part. Why spend £1000+ creating a new one, when you could buy one from Amazon for £50. You could also stock up on spares and have money left over for other things.

Indeed. I wonder if they had a plan B for such circumstances.

Not really that unusual, it's used by the US Military too.

https://www.pyrosoft.co.uk/blog/2007/11/04/army-fly-uav-spy-plane-with-xbox...

I see the communication system is acoustic text messaging.  You would think they would have more than one of these and include automated status reports.  Maybe a beacon that could float to the surface.

I've got to say the juxtaposition of this and the Greek tragedy recently struck me too.  Not really thought it through yet but it's uncomfortable.

Comms with the surface are poor even when working.  They’ve lost comms before, when the ship wasn’t directly over the position of the sub.

Not good.  Along with 'everything is controlled by touchscreens', when condensation must be a problem.

Aye - but when the damn bluetooth won't pair...

More generally - deep sea comms must be a major challenge in a untethered sub.

Probably the blasé presentation more than the machine but that video gave me an attack of the big fat nopes.

jk

I don't know - I find Henry Rollins inspires confidence in most things..

The Titanic is 4km down. I don't think it would be possible to tow 4km of cable to the surface. The pressure down there means the beacon would need to be pretty substantial too.

100%. Cramped tube with a toilet next to the only window. I know next to nothing about deep sea submersibles but in my mind, they were a bit more plush than that for £250k a (no) seat.

It seems trivial to me.  A lump of plastic with a flag on would do the job.  But I was thinking of one including a sonic transmitter and status message.  No cables involved.

I heard it described this morning by a previous passenger as 'spa like' inside. Maybe they put some cushions and a nice throw in for the trip.

jk

Perhaps we should donate 100  50m ropes ?    I wonder what the load would be  ?

Massage, mud packs, beauty treatments, that sort of thing?

Perhaps because games controllers aren't designed with robustness and fail-safe aspects in mind.  Sure they don't often fail but if one should be so unlucky......

If you then take a similar approach to the other elements of design, the chances of something going seriously wrong start to rise rapidly.

It would be interesting to see how much press coverage the Titanic story gets in comparison with the Greek incident. I have a hunch that if a Billionaire or celebrity is drowning, the public are more engaged.          (If only Elon Musk could get involved; he has a spare cave rescue submarine ( never been used), that would be a story!)

Farage was berating the RNLI for rescuing the wrong kind of people. I'm sure he and his fans would be happier if they could get a rib out to the north Atlantic. 

And on subs too.

https://www.washingtonpost.com/news/morning-mix/wp/2017/09/25/the-navys-add...

You seem to be creating a false premise.  There was worldwide concern for the crew of the Kursk.

Again, it's 4km down. Any buoy that would float on the surface would be instantly crushed/popped if it was released from the sub.

I think it'd be impossible to take into account the ocean currents at different depths as it made it's way to the surface to to give an accurate position. The buoy and the sub is likely to move. If it did make it to the surface what's the point in saying the sub is somewhere within an enormous radius? It's only a few metres long.

I've seen an anchor buoy made of 1" thick steel that was dragged down to 800 metres water depth. It was crushed like a beer can. This sub could be at a depth of about 4000 m, at which the pressure and temperature are extremely hostile (about 400 atmospheres and 4 C).

They could use a fluid filled buoy, parafin or similar or have a compensator fitted. The cable attachment would be a problem though, probably need 6km of it to reach the surface

Does anyone know the actual air supply on board? All journalists still seem to think air and ‘oxygen’ are the same thing (!) they are not as well all know. So when I hear claims of ‘72 hrs of oxygen’ are we talking 100% O2 and a C02 scrubber system or are we really saying ‘they have 72 hours of air’ ? 

It could be hollow metal with a pressure release valve.  Indication of the problem would be the main point.

I'm not sure there's much point in us collectively hashing out a design for Subby Mc Subface 2.0 but while we're at it...

Only if it was compressible. You could for example encapsulate a transmitter in soft low density plastic or oil fill a hollow buoy. The electronics then have to bear the pressure directly and there can be no voids whatsoever but that will be how much of the propulsion system is built, soft hollow structures filled with oil so they can be drained and serviced but are effectively incompressible in use.

A streamlined radio buoy would be at the surface in half an hour with its message. It's one of those cases though where the proximity of people and the proximity of help couldn't be further apart, they might as well be in deep space so what's the point of sending out a beacon.

The contrast with the Greek migrant tragedy and the question of press attention is fair but submarine accidents, particularly the idea of initial survivability, I think that really triggers people's sense of horror and morbid fascination. Anyway, real people still missing and missed so enough of that.

jk

Because that's not how you design safety critical systems. A robust safety case would have to be able to demonstrate appropriate reliability standards have been met. That means using tried and tested components, not parts made for toys.

Most DSVs have some sort of pressure resistant float. Normal ballast systems won't work at really deep depths, so they are made to be positively buoyant and have jettisonable ballast. When released from the support ship they sink, then to surface again they jettison the ballast. The earliest designs, various iterations of the FNRS II and the Trieste used a big tank full of petrol, as it's sufficiently incompressible and less dense than water. More modern versions use 'syntactic foam', which is made of lots of tiny spheres, often hollow glass or metal, suspended in some sort of polymer. These can survive the pressure at those sorts of depths and remain buoyant.

Design details for the missing sub are hard to find. It doesn't look like there's much in the way of external floatation in the pics I can find, but the pressure vessel is very large compared to other DSVs so might be enough to make it positively buoyant on its own. It's also partly carbon fibre construction, which is unusual, but would possibly be lighter than the more usual steel or titanium. Might be cheaper to construct but I wouldn't like to say for certain. Interestingly it has a system for measuring stress in the pressure vessel, which is not something I've heard of before, in more traditional subs you just rely on a massive safety factor in the design.

Can't help wondering how the ballast jettison system works. They're normally fail safe, e.g. electromagnets on Trieste.

There's an account on BBC news from someone who's been in it before and said the hatch is bolted on from the outside. It certainly lacks any kind of conning tower typed structure, which is normally used to provide an exit route when on the surface, so even if they're bobbing around somewhere waiting to be found there'll still be an issue with breathable air.

I can't help wondering if it's been built on the cheap and has a lot of design flaws. 

I understood the support ship was directly overhead.   In range for the sonic communications.

I suspect we might hear more about it in due course.

Given there's no kind of submarine certification authority like there is with aircraft, plus it's a private company, they might not have done a proper safety analysis of it.

"The contrast with the Greek migrant tragedy and the question of press attention is fair but submarine accidents, particularly the idea of initial survivability, I think that really triggers people's sense of horror and morbid fascination."

It's similar to the Thai boys football team trapped in a flooding cave - nobody knew if they were alive, or could be saved even if they were. It quickly became a world wide rolling "live" news story and , thankfully, a happy ending with some  heroic and interesting characters involved - cue fantastic documentary and less fantastic movie.

If we already knew this sub had imploded from catastrophic failure then I think the story would have quickly died with the passengers as interest wained.

As said in the video, it's designed to be thrown around by teenagers.

And the fail safe, bring a spare or five.

I remember the bloodhound used the trigger from a cordless drill for the accelerator. This is a 1000 mph "car" and they said they couldn't engineer anything better. I'm guessing they used two or three to check for inconsistencies.

At the risk of sounding waffly, I think the important thing is to remember that just because you think that that horrible thing is getting less attention than it deserves compared to this horrible thing, it doesn't make this horrible thing any less horrible.

Quite, but not for say driving a submarine.

Which is fine unless the flaw is generic e.g. affected by moisture or whatever.

Who knows, maybe it's fine, maybe they are fine, but I'd want a bit more assurance, than "it works for teenagers in a heated living room" if it was me. As reported it all looks very Heath Robinson.

the last time I had a look at a military drone training facility, they were using xbox controllers and sat in what looked suspiciously like gamer chairs

The company website mentions use of COTS (commercial off the shelf) equipment a fair bit.

There's nothing intrinsically wrong with this approach, it's generally a good idea to see if you can use COTS stuff before you design something more bespoke. However there's a reason a lot of parts on a sub are not COTS, not many parts are designed and certified for the kind of environment a sub is in or come with the kind of failure rate that is generally needed. When using COTS equipment like in some of the examples people have mentioned, then generally at least one of the following conditions apply:

- it's not a safety critical part

- you've paid the manufacturer to re-certify it for your particular use

- you've tested and certified it yourself (assuming some sort of certification regime exists)

In this case, I can't help wondering if any of the above apply. The second two options are often costly. One account of the sub mentions the Xbox controller, a couple of touch screens and only a single button. I would hope that the lone button is for the ballast release. One might reasonably expect some sort of redundancy in the manoeuvring control system though. So if say the Xbox controller fails, there might be some sort of control available via the touch screen (often know as 'under glass'). If the computer the Xbox controller is connected to has a failure, then this would result in failure of the screens too, unless there's a backup computer available. In properly designed stuff, there's almost always a backup physical control for anything safety critical that's under glass. E.g. for this sub one might reasonably expect some sort of physical switch to give at least basic forwards/reverse control of each thruster. If not then multiple layers if redundant computer systems as is the case for a lot of aircraft systems where physical switches aren't practical. Without knowing more details it's all just speculation though.

Of course it might not be down to a design flaw, it could just be tangled in some wreckage or something.

If it’s wired the big issue is that the USB interface is not robust enough - all the spare controllers in the world are no use if you’ve buggered up the socket they plug in too.  MIL-DTL-5015 connectors look like they do for a reason.  

The whole chain from controller to dive plane or weight release needs to be up to scratch for life critical systems.  Starting with a consumer controller doesn’t preclude that but it’s not as simple as having spares as consumer controllers tend to talk to…. Consumer electronics with consumer level software.  I’m sure military applications have taken all due car to integrate consumer controllers.  

Why not for driving a submarine?

You might almost have expected a slightly higher-tech one to be driven using something like an iPad...

I mean, an Airbus aircraft is flown using a joystick that isn't really substantially different from a premium video-game one, give or take a LOT more testing!

The people you recruit to fly military drones are...gamers.  Why not have them do it using the thing they've got thousands of hours of practice using before they've even stepped in the door?

I think you've answered your question 

There's a difference between something being physically tough and something that knows the difference between a failed transducer and one held at full deflection and what to do in each case. If you're playing a recreational videogame the distinction is irrelevant, you pause and address the problem, probably by connecting a spare controller. If you're piloting a vehicle it's critical that the system can recognise the difference and the vehicle goes into a defined safe state while the issue is addressed instead of, for example, full ahead.

The BBC were running a story from a previous mission where a calibration error of some sort in the controller (or its interface to the sub) had previously resulted in loss of control at depth, the sub would only circle one way. It was apparently resolved after some discussion with the surface by 'holding the control differently', presumably the pilot manually introducing an offset trim. If accurately reported then that's not a description of a well implemented safety critical system!

jk

This. It should be relatively simple to pressurise a buoy on descent to resist the water pressure, and have a bleed valve to stop it popping on the way back up.

As others have said, it probably wouldn't do much good popping up and sending a position miles away from the release point (although oceanographers can work wonders with modelling - IIRC they located a womans murdered body in the sea based on where the cadaver dogs (sat in a RIB) got a whiff of the gas).

I'm surprised the sub wasn't tethered. Weren't the early bathyscaphes that went to the bottom of the Marianas Trench on cables?

As has been pointed out, they seem to survive abuse from kids and the military. Joysticks / controllers have been around for 40 odd years. There are perhaps many millions of hours play put through certain models of controller. Far more testing than even Nasa could muster.

I'd also suggest that there may be some observer bias. A journalist commented on the one or two things they may be familiar with, rather than the hundreds of other things that go to build a deep sea sub, that may not be so common.

Agreed and I'm not actually complaining. I can see why this story is getting attention in the way the Greek sinking maybe didn't.

jk

For playing video games, not controlling safety critical devices. Maybe it was all tested and safety properly considered, but it raises questions at the very least.

Nope. Some very early bathyspheres were lowered on cables but they just dangled off them and couldn't manoeuvre anywhere. They only went a few hundred metres, maybe around a Km tops? To get deeper early explorers switched to the petrol float and releasable ballast method, have a google of FNRS 2 and Trieste (Trieste was the first vessel to reach Challenger Deep). I think lots of oil and gas subsea stuff is tethered, but for really deep depths it's not really practical. For one thing it's hard to make a tether that won't snap under its own weight but can still be dragged around by a sub without messing up its buoyancy too much.

Edited for spelling 

Fine, as long as there are less convenient, but reliable controls to fall back on.

In other double standards news UKC as a collective seems quite happy to discuss and speculate about this incident but not climbing incidents.

Which is fine if you're piloting an un-manned drone where, if all goes to pot, it'll have a fail-safe to autonomously return to base or land at nearest friendly location - hopefully, the worst case would be that it falls out of the sky and crashes somewhere uninhabited.

Rather different thing to be relying on it to pilot a manned sub in pretty much the most inaccessible, and hostile location on the planet, where a failure means pretty certain death for all involved.

Interesting that it's reportedly of titanium and carbon fibre construction (BBC said fibreglass). The end caps are clearly metallic, Ti presumably, forgings and the machined seal flange at the 'door' end looks to be the same material (metal-metal face seal?). So where is the carbon fibre? Presumably the tubular portion but it seems such an odd material choice given it is comparatively rubbish in compression, drawing far more heavily on the binder/matrix properties to prevent failure by fibre buckling and delamination than it does in tension where the fibres do their extraordinary thing. Also, the composite tube to metal flange joints would be a nightmare! I can't see the benefit over just having the whole tube forged. Presumably it's Ti vs Steel for weight reduction, saving on external floats which could be lost or damaged in a collision. It looks like without floats the hull wall in steel would only be 4-5cm thick for neutral buoyancy, that feels too thin to me. In CF it could be 4 to 5x that or 2x in Ti.

edit: apparently it's bigger than it looks! Walls could be significantly thicker than I estimated without needing floats

I wonder if it's actually just the fairings and thrusters rather than the pressure hull that are CF but then the talk of hull condition gauges at least hints to me at composite construction.

jk

I read the navigation was determined from the support ship and then communicated down.  So was this using the transmitted acoustic pulses, rather than reflected sonar ?  Otherwise it seems too much coincidence both failed the same time.

I hope they all get out - stuff of nightmares.

They showed the Kursk dramatisation this week on BBC4 (?). One of the issues was the backup rescue vehicle was sold off 'for rich tourists to see the Titanic'. Clearly not the same vehicle but an odd coincidence.

Isn't sonar just acoustic pulses?

They're clearly all dead, or waiting on the seabed to die. I'm not sure they'll ever find out what happened.

Sonar and radar use powerful transmitted pulses and detect tiny reflections.  But much lower power can be used if the pulses originate from the target.  (Until they don't.)

Yes but they are fundamentally the same thing.

If the sub is intact and there's a will to salvage it then they will. For example, it may have suffered a control failure and embedded itself in the wreck, comms broken and unable to escape.

True, but it's all manageable I would have thought.

If it got stuck on full throttle, big red panic button to put it in safe mode. Swap controller. Resume. All the movements in a sub are slow so you've got time to deal with somehting.

I'd be worried however if one of the buttons ejected your ballast or some other irreversible action.

I don't get it. I would have thought one of the challenges of making a tin can a submarine is making it heavy enough in the first place to sink. But maybe by the time you make the materials thick enough to withstand the pressure, too much mass does start becoming an issue. Especially on smaller units, but it still surprises me.

Saying that, I still look at passenger planes and can't fathom how the maths checks out that they can actually fly so my intuitive reasonings are known to be quite off on these things.

It's relatively rubbish in compression, but in tube form the fibres' stiffness is doing work. Think about a fishing rod or any other tubular long fibre reinforced item used where resitance to bending is required.  The fibres running around the tube are resisting deformation. Tubular carbonfibre struts holding up a weight would be an example of erroneous use - in that scenario it's the resin that's doing the work because the compressive forces aren't trying to flex the tubular fibres, they're just trying to crush them along their length.

Also, any compressive forces on the tube will be happening from every direction, thus balancing each other out - it won't be like someone standing on the side of a tube and squashing it flat.

Presumably from the description given the dived sub pings periodically and the service ship triangulates its position using GPS equipped passive sonar buoys. It's no good all the network nodes being effectively overhead and sound propagates very strangely through stratified water, there will be dead rings where the sub's pings can never reach the surface and other areas where they arrive with one or more echoes. The triangulated position can then be acoustically telegraphed back to the sub +- a likely significant error hopefully allowing it to motor to within its onboard active sonar's range of the Titanic.

No idea what part of that if any failed, when or in what order, the reporting isn't clear enough.

jk

https://oceangate.com/images/titan/renders/titan-components.jpg

This seems to confirm it's a titanium hemisphere at each end, joined by a CF tube.

Initially, I'd thought it was a reporting error and the pressure vessel was entirely titanium and the outer light hull (the hydrodynamic shell) was CF.

Edited for terminology

That's true for isotropic materials too, they still ultimately buckle and crush under enough hydrostatic pressure.

The point about CF is the individual fibres are so slim that despite their stiffness they individually have next to no buckling resistance without the epoxy matrix for support which is relatively very weak. In a conventional layup* there are no fibres running through the thickness of the part so the failure in compression is usually by buckled fibres delaminating layers from each other. Basically conventionally applied fibres don't add anything like as much strength to the part in compression as they do in tension.

Something like a CF fishing rod is sized to prevent the lower compressed side failing by crushing/buckling or the tube flattening out, the upper tension side as a result isn't even breaking a sweat. I've got a quite impenetrable but fascinating book on composite structure design and if memory serves, where the loads are really predictable it can actually be lighter to use glass fibres in the compressed side of a part than carbon despite the density and strength difference because they are, individually, significantly fatter and therefore less prone to buckling and damaging the matrix.

*in fairness there are other forms of epoxy carbon with random fibre orientation in all three axes giving it isotropic properties (so called 'forged carbon'). Not sure how it would compare to something like Ti though.

jk

Good find, I'd love to know how the Ti flange and endcap are attached to that tube. And why.

jk

Yeah agree, odd choice. I think I read somewhere this morning that it is indeed ti end caps and composite tube section. I'm sure I saw a wall thickness of about 5 inches for the tube stated somewhere but no idea if this sounds about right.

I'm not sure exactly how submarine pressure hulls are actually made, though from what I've seen it involves steel rings which are welded together. Don't know how the rings are made, I guess forged maybe? All I can think of for choosing composite is that there's potential to do it more cheaply. Making such a structure from metal would require some fairly hefty machinery to cast or forge or whatever (apologies I'm no metallurgist and have never been much good at mechanical engineering, maybe someone a bit more clued up can chip in). You've then got to weld the parts together which would need a fair bit of skill, plus you might well want to do some xray or ultrasonic inspection. This would hence have to be contracted out to a company that can deal with this sort of work and would not be cheap. If you use composite, while it's labour intensive it doesn't particularly need any specialist equipment so could be done in house. The forces involved, while very big, are pretty much in one direction so I guess you won't need any kind of complicated layup, just lots and lots of layers.

 Metal tube (cotton reel) wrapped with carbon 12.7cm thick, pics on their website. Still, as you say a curious choice. 

None of which is particularly difficult or novel. A vessel of that size could be made easily enough, I regularly inspect much larger pressure vessels of thicker wall thicknesses made in one or two pieces vessel and lid/inspection port. 

Yeah sorry wasn't trying to say it's novel, just potentially expensive to contract out compared to wrapping loads of cf round a tube in your own workshop. Happy to be corrected though, just trying to think of why you might build it that way rather than the tried and tested approach of a big metal tube.

The only other thing that springs to mind is they did it just because they could. It's more 'exotic' than metal and I've certainly come across a few engineers who'll push for a solution that they personally find interesting rather than using a more 'boring' traditional and well understood method. Sometimes decisions like that get made to increase in house expertise too with a long term view of cornering a particular market.

ETA: I think I'm probably being influenced a bit by the scale involved in military submarines. With those, while it's not difficult in principle as you say, the scale involved means it's a bit of a big job. As you say, this vessel isn't all that large

I believe the reporting says they lost communication and position at the same time.   I suggested the likely reason  (unless it was a sea monster).

SpaceX’s COPV failure showed that carbon fibre under extreme pressure has at least one failure mode that apparently nobody had been aware of.

One article I read said the hull has sensors embedded in it to monitor for possible failure.  That says something.

Presumably if that was the case you'd just dump your ballast and surface. News reports have mentioned a surface search taking place.

Which begs the question, why would it not get found pretty quickly via an EPIRB or similar? If it wasn't fitted with one, that would quite literally be criminal, at least under UK law anyway (obviously that doesn't apply here, just emphasising the point). It may well be a possibility, but if it was just a case of loss of navigation data and nothing else then there would have to be some serious deficiencies in design and operating procedure for it to be planning out like this 

You mean, if they no longer knew their position ?    I hope they could surface without power, or the computers working.

Apparently the weights are attached using soluble 'things' which should ultimately dissolve and allow it to pop up if it's not snagged. No idea on the dissolve time though.

Would reduced weight be beneficial in terms of ballast management? Indeed, would it actually be lighter than the equivalent strength Ti, it could actually be heavier.  I'm wondering if it's to do with thermal management and comfort - apparently you sit on the floor/walls in it and the walls are electrically heated. I can imagine a Ti body in 4degree water would require huge amounts of heat to keep it comfy/not covered in condensation over the course of a 10hr dive. Yuo can't insulate it externally because the air pockets would be crushed, and you can't do it internally as you'd lose space. Therefore a fuselage that isn't leaking heat like mad would be desirable.

Edit - thermal conductivity of CFRP 'out of plane' is 0.5-0.8, iron is 80, aluminium is 210, titanium 20 (W /mK). Thus CFRP is ~20-40 times less conductive than Ti. Perhaps even more so if it has to be thicker to get the same strength.

Thanks for the clarification.

You can get 6km comms cables for deep sub communication.  

Oh god, Amphenol connectors!  That takes me back. Someone had wired the power cables for a wind turbine roof actuator with those, and getting spares is a nightmare! Each tiny part seems to have its own reference number...

Count yourself lucky you weren’t working on a device with the Soviet equivalent…. We only had a fixed number of the female connectors to go with the device and we’d sure as heck not have been able to get any more.

For most applications there are automotive connectors that are good enough and overcome the issues with consumer electronics connectors.  I’ve had to very carefully remodel a couple of USB connectors that have been mashed up and it’s not something I’d want in a life critical system.  That’s before I open up the now closed part of my memory labelled “Writing a Windows XP USB 2.0 device driver”.   Ugh.

One way of rating how geeky someone is, is by asking how many personal items they own with a NATO Stock Number; 2 for me - a rucksack system and a watch.

But, if CF has to be thicker, that means a metal device can take conventional insulation - much less conductive than CFRP - within the same volume envelope.

I suspect the primary advantage of CF here was cost. At the off-the-books expense of introducing seams between materials with different CTEs and of using CF material in a relatively uncharacterised regime.

In some ways this reminds me of Apollo 13. It grabbed the worlds attention in a “will they make it back” kind of way. Hope they do obviously.

Banging noises have been heard (check bbc).  I heard that even if the vessel surfaced it can only be opened from the outside. Fingers crossed.  

Furry Dice allegedly used to have a NSN in the 1970s/80s.

 Thousands, literally from complete units down through sub assemblies to components.  Though it is a National Stock number, strictly speaking.  99 for UK.

I have one or two DMM krabs with NSNs didn't know it when I bought them iirc from one of the caving shops in Ingleton years ago

Sounds like they've "heard" some distress signals coming from the sub - the ol' "Bang on the side with some metal at regular intervals" actually seems to have worked.

I just can't fathom how, even if they find it in time, they'll get the sub up if it's at anything remotely near the depths it can operate.

Must be utterly horrendous for those onboard.

There's also the chance it's floating on the surface from what I understand? Doesn't help that they're still sealed in - which is arguably worse in that situation

If it is on the surface I would like to know how the hell this vehicle does not have some completely independent location signalling system especially as you cannot apparently open the damn door!

Yeah - there's a lot of "why didn't they add..." around this submarine.

Speaking from a point of huge ignorance - an emergency "Get to the surface and start making pinging noises" function seems like a bit of a no-brainer.

So does a hatch you can open from the inside though...

There is a fairly damning appraisal of the vessel from an ex-Navy man. 

https://www.telegraph.co.uk/news/2023/06/21/ex-navy-admiral-chris-parry-mis...

Also included in that article is the suggestion that 'old scaffolding poles were used for the sub’s ballast', which hardly inspires confidence. 

To be fair some of the ballast is disposable i.e they get to depth and dump it, so no point in using something of value. there are also trim weights placed around the vessel as required for each dive, which stay attached.

Still think its a budget build, little more than an diy project

Missing Titanic Sub Once Faced Massive Lawsuit Over Depths It Could Safely Travel To
Court documents reveal a former OceanGate employee had several safety complaints over the tourist submersible—and then he was fired.

https://newrepublic.com/post/173802/missing-titanic-sub-faced-lawsuit-depth...

The observation window was certified to 1300m rather than 4000 m depth of Titanic.

Quote from URL:

At the meeting Lochridge discovered why he had been denied access to the viewport information from the Engineering department—the viewport at the forward of the submersible was only built to a certified pressure of 1,300 meters, although OceanGate intended to take passengers down to depths of 4,000 meters. Lochridge learned that the viewport manufacturer would only certify to a depth of 1,300 meters due to experimental design of the viewport supplied by OceanGate, which was out of the Pressure Vessels for Human Occupancy (“PVHO”) standards. OceanGate refused to pay for the manufacturer to build a viewport that would meet the required depth of 4,000 meters.

Door likely opens outwards so the pressure improves it's seal, but a means of opening it would still make sense. 

In other words a design safety factor of <1 which doesn't sound like a fantastic engineering decision...

Farcical that it often comes down to banging on the hull,  when the computers and power have failed.  It would seem simple to have a much more efficient and automated device for this.   But maybe the scaffolding poles were good after all.

Sonar is all that works at those depths. It's rudimentary banging, but it works. A distinct old school ping might be easier to triangulate though. 

Only if someone is still capable.

Would this part be all that difficult?

Assuming it's not stuck somehow, using a unmanned vehicle they could just strap something floaty to it. A bunch of empty aluminium dive cylinders comes to mind, but there must be something better for job.

Add a load of ballast to get them down there, hook it to the sub (do subs have toe hooks, they get craned in the water so I assume so), cut the ballast and watch the rocket go (slowly). 

The difficulty is getting that level of specialist kit, including the support vessels, to the location of the missing sub before the air runs out.

I also suspect practicing 'just strapping something' and a bit of cutting with a ROV in a swimming pool or dock is massively less difficult and time consuming than doing it 4km underwater.

TBH if you're incapable of banging on the hull every half hour you're going to be dead anyway by the time they find you.

A friend was involved as surface diving support when James Cameron was diving the wreck. She said they had that many issues with the equipment that she would have declined the offer to go down in the sub if offered the opportunity.

I can't see how opening the door would help - the pressure and temperature outside (and inside too, once the door was open) would simply kill them, wouldn't it? And if they had some way of surviving that, they'd be almost immediately mad from nitrogen narcosis - and it'd be impossible to avoid lethal decompression sickness on the way back up due to the timescales required. (Assuming they're at or near the Titanic's depth.)

I think, at those sorts of depths, you just can't leave the sub - either it gets back up with you in it, or you don't get back up.

For one, a few more hours is hugely important.  Secondly, banging a random point on the the hull will have a tiny fraction of the range of a proper external device, which could also carry meaning.  Not using up the oxygen,  and saving enormous resources,  possibly even lives,  on the search and recovery.

Yep but if they were sitting on the surface still sealed inside and slowly suffocating for want of a door handle then it would be helpful 

It's more that if they surface miles away, can they open it themselves or would they still suffocate? 

I would hope the vessel and the kit is already in position and just need the location of the sub to get on with their task.

True, but they've already been doing this sort of thing recovering artefacts from various depths over the decades so it's nothing new. Provided they have the right equipment and people to hand (which they should, its day three now).

They will already have the recovery plan ready. They just need to know where and hope it doesn't include any unexpected complications. 

As discussed further up the thread - that might work at shallower depths, but not at the extreme depths we're looking at here. The cylinders you suggest would be crushed flat long before they got that deep.

I've seen a suggestion of using an ROV to attach a cable - the US Navy (I think) have one that's capable of operating at that depth, but it's not even in the vicinity and will take too long to get there.

Picking up a few lightweight artifacts is in a rather different league to manouvering a cable strong enough to raise the Titan.

They have no chance of raising it - even if they find it.   Its too deep, and has a few others have said, raising something of this size from this deep hasn't been done before.*

*Although I do believe the Americans brought back a portion of a Russian sub some years ago, but I can't recall any details.

Did you see the documentary? It was on PBS America a while back. Cost as much as a moonshot and took years and the lifting cage failed sending half the sub back to the bottom. They thoughtfully gave the Soviets some bodies back.

Bollocks - it's designed to be neutrally bouyant isn't it? It would not require much force to actually raise the thing if it is intact and the ballast removable.

Regarding location via the banging. I wonder how accurate a multilateration approach can be using sonar buoys. Probably not good enough.

Out of interest, does anyone know what resources were scrambled for the hundreds in the Med?

It looks like the French have sent a special underwater robot. Already reported that:

"two C-17 US military planes arrived in St John’s in Canada at 19:30 local time (23:00 BST) with supplies for the search and rescue mission. Another one is scheduled to arrive later on Wednesday.

A 747 is also on its way, carrying equipment to aid with the search, the US Coast Guard says.

Cranes were loaded onto a Horizon Arctic ship late Tuesday night, which was docked in the harbour of St John’s.

It has since departed, along with two other Canadian Coast Guard ships, to the site of the Titanic wreckage. "

Also interested who is paying for this?

This is designed to be raised unlike everything else however.  If it’s designed for the external ballast to be easily removable by a DSRV manipulator arm it’s entirely possible for it to raise itself with a little help, if it can be found and is intact.

Are you sure?

Diving cylinders are rated for around 4000 psi. Pressure at titanic is 6000 psi. Granted it's external pressure instead of internal, but I'm pretty sure they would still hold. I'd like to think I've got a fair factor of safety on my back. 

Even if they are not deemed up to the task, there will be something can can work as a float at that depth. 

A drum full of oil would probably work.

I think petrol was commonly used to lightweight submersible craft in the early days as it is lighter than water but not very compressible. But as explained aboveis it really necessary as the craft is neutrally buoyant by design.

Stuff of dreams, send a rv down, locate another rv in pitch black below 3000m, attach anything that will recover it etc.. that's days of work even if machinery and the weather is onside, not hours. 

I guess it depends why it's stuck down there. If ballast can't be ejected due to something jamming, or it's taken on some water. Or maybe it's trapped under something and just needs an initial uplift before it can finish on its own.

according to the guy that runs the company there are only 4 vessels capable of operating at 4000m depth and they're in one of them...

But he's come out with some very spurious comments about the whole operation so could be rubbish...

theyd still suffocate the hatch is secured with 17 bolts from the outside...

For something so dangerous there are literally zero safety features ... they even opted to not fit a rescue beacon despite getting lost for 5 hours on a previous dive

The nearest comparable* operation I've seen referenced was the US recovering their crashed fighter jet from very nearly as deep as the Titanic. Mentioned in the final paragraphs of this story...

https://www.bbc.co.uk/news/world-us-canada-65965665

But that particular ROV reportedly isn't on location. Others that can operate at the depth of the Titanic are apparently on the way but I don't know how long they're supposed to take and there wouldn't be long left. I've not seen anything about whether there's a suitable crane to do a similar process to the fighter jet, and I'd imagine (with no qualification to hold an opinion at all) that the process of getting down there and making attachments would be time consuming enough to make feasibility questionable even if they found the sub right now and had everything needed on location.

*That is, if it's found on the seafloor and needs lifting

BBC is reporting that one suitable for operating at the depth of the Titanic has arrived. But will still take a couple of hours to prepare and then several more to travel down.

Too many 'ifs'

.. they even opted to not fit a rescue beacon despite getting lost for 5 hours on a previous dive

I read/heard that did have some kind of active or passive transponder on but contact was lost during the dive.


 

That's not much point in this thread if we can't speculate.

A beacon wouldn't transmit through 3000m of water. 3000m down is another world, no light, no gps signal, no radio signals, you move with the currents as you descend but don't know which way and by how much, they then have to use maps and deduce where they are on the bottom. It's on the limit exploration and if you push those limits repeatedly, percentage chance will eventually get you. 

I agree.  But it’s less ifs perhaps than raising an equally hard to find artefact, which was the comment I was making.

I’m surprised Elon Musk hasn’t jumped in with a solution; too busy costing up to Robert Kennedy Jr it seems.

As crazy as this is at -3000m, the Mariana Trench, -10,000m, 2000+km long, 60+km wide. 

There's some interesting toys out there for working on the ocean floor, cable layers that dig a trench lay the cable and back fill it at 2500m.

Some of the newish  (10+years when I was playing with it) oil extraction equipment is now tested to 4000m, as the wells go deeper and deeper. 

Aircraft black boxes have ultrasonic beacons that work down to 6000m depth.

Channel 5, crass?  

They've obviously upped their game from unwatchably crass then.  They are the televisual equivalent of the Daily Express.

(If I was a family member of a possibility deceased billionaire, I'd have my legal people watching the programme.  Channel 5 will see that as a positive as at least it means that they'll have some viewers.)

T.

Fair point !! 

Back in the eighties (yes, I'm that old) one of the guys in the office was an agricultural engineer designing subsea ploughs to bury cables and pull them up for repair. Back then they didn't bother to bury the cable if the sea bed was beyond the depth reached by fishing nets and anchor cables. 

Exactly, as I said up thread, only sonar works, a device that gives a 'ping' that can be triangulated. (I'm Ex SAR)

But navigation, locating and attaching is key? Trench layers don't really care if it's laid plus or minus 10, 20, 30m left or right, it's irrelevant. Dragging a trencher on a 3km cable isn’t the same precision as is needed to hook what must be a 10m sub? 

Yes, a million times easier to catch and pull up a cable.

Sadly they seemed stuffed unless they have some contingency plans they've not publically stated. The more you read, the more it sounds like nothing is backed up, there is no secondary anything and if something fails it's a case of hoping you can return to the surface unaided.

Is there a technical reason they couldn’t have an Emergency Satelite PLB on the sub for the eventuality they ended up on the surface?

Is there a technical reason they couldnt have an airplane style  acoustic black box on the outside for the eventuality they ended up on the bottom?

If they could have fitted this stuff and didn’t surely that’s criminally irresponsible. It would be like taking a party out on the hill but not packing a mobile phone or a whistle.

A sonar transponder on the submarine will let you find within a few metres. This was possible 20+ years ago in subsea well intervention.

Not really my point (BTW the trenchers drive along the sea bed) , however ROVs with manipulators are very impressive bits of kit these days, but as you say locating it is the first problem.

Some of the pictures of the sub show it with a lifting sling around it, so that would be a bonus in a recovery situation. 

True. Ask any JCB driver.

Of course, if they have the kit on scene and this lot seemed to be a bit cowboy-ish in terms of safety measures. It took weeks to locate the Air France black box at 3900m in the Southern Atlantic. They don't even know for certain if what they heard was actual banging from this sub.

They could fit all sorts, plb, sonar pinger, hatch that opens from inside, flares, emergency food supplies, an emergency raft to pushes through hatch... sadly they've nothing.

One report said the reported bangs were half an hour apart. Thats consistent (according to an ex submariner I used to work with) with the standard search procedure for a missing sub. On the hour and half hour all the search vessels go silent, switch off active sonar and just listen. The missing sub starts pinging with sonar (if available) and makes as much mechanical noise as possible.

It occurred to me last night that in all the talk of air supplies, I've not yet seen any report mentioning what food/water they have on board. Obviously, air is more important, but water is going to be crucial, too.

Not by lunchtime today it's not.

Maybe they are realists, if you have no means to open the hatch even if they surfaced, getting in gives you 96hrs of life span, any supplies that might last longer than that are a waste!! They should finish up in court as they certainly appear chancers. 

There were a few safety systems on board that I thought were interesting. One of which was an automatic ballast release that react with salt water such that if the sub is in the water for more than 24 hours, it will automatically surface.

Since comms were lost on the decent, I can't believe that both the normal ballast release and the auto backup ballast release both failed. Seems too unlikely.

This tells me it's either on the surface and they are looking in the wrong place, or it sprang a leak on the way down and it was all over on Sunday.

Unless of course the loss of comms is completely unrelated to the sub not returning and it did make it to the Titanic and got stuck somehow.

If the noise is coming from within the sub that is cause for a glimmer of hope at least.

It would also rule out lost on the surface (as should capable radar), implosion (you'd assume navy hydrophones would have registered that and the information would have fed through discretely to the coastguard by now) or catastrophic flooding (probably any since problematic and catastrophic at 6000psi are basically the same thing). Lost communication, equipment which would also be serving as a locatable beacon, and the fact they've not surfaced suggests some sort of electrical system failure but that alone shouldn't account for the failure to surface. Whatever happened must have lead to (or resulted from) them becoming physically stuck in mud or wreckage. Or, worse, the failure mode was not considered and adequately mitigated but it would be unbelievable if there is not at least one layer of fail safe design to release the ballast.

jk

Water is supposed to be 3 days to about a week. Considering they arent going to be moving much and its fairly cold I would guess even if they hadnt brought down a couple of bottles the air supply will be the deciding factor.

Single point failure? Both normal and backup ballast release actuate the same clamp (that's jammed for some reason)?

I'm not exactly getting a warm fuzzy glow about the number of independent and diverse safety systems or fault tolerance of this particular sub.

K-129, partially recovered from 4.9km depth by Project Azorian.

https://en.wikipedia.org/wiki/Soviet_submarine_K-129_(1960)

That was in the 1970s and used a grappling system from a built-for-the-purpose surface vessel which operated under the pretence of attempting to mine manganese nodules from the sea bed.  I'm not sure whether there were any ROVs involved.

In reply to ExiledScot:

I'm not sure that a Winnebago would be a sensible vehicle to use for the original dive, let alone the recovery operation...

Their multiple redundancies do seem to boil down to "hit it again but with a bigger hammer".

I'd really hope not. I assume by using a "?" you're wondering whether there's a single point of failure, rather than you know there is one.

The hull was part developed by NASA, I find it hard to believe that they would overlook really obvious and basic single points of failure like that. But who knows?

I very much doubt NASA were involved in the overall design, more likely they were involved in the carbon wrapped tube only.

Just speculation on my part.

That's just the hull.

Also:

"Minimum safe temperature for launch is 31 degrees Farenheit, it's currently 18. Yeah, I know we've known those 'O' rings are a bit brittle since 1977 and you booster guys want to postpone launch, but it'll look good on TV"

And:

"It's only a bit of foam, it'll only cause minor damage, we're not going to get imagery of any damage just because those pesky engineers are worried again"

(Challenger and Columbia)

That NASA?

The company that manufactured the porthole only certified it to 1300m, so there's one pretty big single point of failure with, as someone pointed out upthread, an unusual design margin of <1. NASA might not overlook single points of failure but the guy who actually built it clearly has. I suspect he's learnt an important lesson in designing for safety, but it's looking increasingly unlikely he'll have chance to put it into practice.

Apparently this is the chap to haul it up but there's virtually no chance of it getting there on time even if they find it.

https://www.navy.mil/Resources/Fact-Files/Display-FactFiles/Article/2418245...

Maybe.  The hemispherical end caps will defocus their return signal, and the CF part may not give a good return depending on the details of its composition.  It's pretty small as well.

As stark as that bit of the story sounds I suspect the reality is more nuanced and largely to do with who carries any liability. Does it paint a picture of a really careful, safety first approach to design and delivery or does it smack of someone pushing hard to do something exciting and corner a market? I have my opinion but it may not be quite as straightforwardly bad as the reporting of the issue makes out, not least because the window clearly has survived several full depth dives and, apparently if the sounds are people knocking, this one too.

One thing that will come from this eventually is answers because given the resources of those onboard (and their families ashore) you can pretty much guarantee it'll be raked over in the courts in the years to come whatever happens in the next couple of days.

jk

Firstly thats the hull and not such things like the release mechanism.

Secondly I would wait to hear from NASA what, if anything their exact involvement was. Both Boeing (who failed to put redundancy into their 737 max MCAS) and University of Washington have challenged the claim they were involved.

For the university for example Oceangate claims it was a 5million multi year project. The university says it was cancelled early after about half a million was spent and was for a different sub intended for shallower water.

Boeing have simply said they werent a partner and didnt design and build it.

Looking at the size and shape of it I doubt it sits very far above the water when surfaced, so would pretty much be invisible to all but airborne anti submarine radars that can spot something as small as a periscope. For these kinds of aircraft the wake of a periscope is often easier to detect than the object itself, but this wouldn't have any wake as it would just be drifting. Still, there'd hopefully be at least a sizeable chunk of metal to create a radar return, but only for a small number of highly capable systems. The hemispherical shape shouldn't be too much of a problem for an anti sub radar. In fact from the right aspect the radar beam might go straight through the carbon fibre and bounce round the inside of the metal part which would act as a very effective radar reflector. Definitely needle in a haystack stuff though anyway. Might well all be academic if it's not surfaced anyway 

I wonder how low it sits in the water when surfaced, whether a radar reflector under the fairing would be fully flooded. Can't think why you wouldn't include one or at the very least some quarter wavelength foil tape strips.

jk

Much more effective would be an EPIRB.

A radar reflector on a small mast would probably be a good call anyway though. You could even mount it on a small conning tower typed structure that would allow you to open an escape hatch when surfaced without flooding it, something that everything since the first bathyscape has had (the first one, FNRS 2 didn't, but was subsequently redesigned to include one)

Yes, indeed - I just thought it was odd that I hadn't seen any mention of it. Ironic (and grim) to be thirsty when surrounded by  all that water.

I've since seen a couple of passing references to "limited supplies" on board, but that's it.

This has been noted before. Are you planning to attend any weddings this weekend?

We can't know that, though - they seem to have started with about twenty person-days of air and we don't know the status of each of the occupants.

A person will suffocate before oxygen reaches 0% in the air, even once down to 10-15% in air it causes serious problems, especially with the build up of carbon dioxide. 

Yeah, but we don't actually know whether they all survived whatever went wrong, or what might have happened since then.

Blunty, if there are fewer of them breathing it, it'll last longer; we can't know just now.

So, if you realised your fate early on, bit like the kids game app Among Us that they robbed and turned into TVs Traitors, you kill the others in there immediately, you quadruple the time you have waiting to be rescued. Not sure if that Darwin's work or not. 

It's a really dark line of thought; there's potential for some really horrible dilemmas as time ticks on. Isn't one of them in there with his son?

As it's made from titanium and carbon fibre - i'm assuming it won't rust or corrode. If it is snagged on the Titanic (which is corroding as made from iron) then it might eventually come loose and rise to the surface in perfect condition in 100 years time or so...

In this scenario, I think the obvious choice is the pilot and company owner, he designed the thing with virtually zero redendancy and safety features, charged them a fortune and made them all sign a ridiculous waiver absolving himself from all liability if something went wrong.

From the pictures I've seen, with all the loose cabling, the slings strapped to the top and the thrusters that stick out, it would only need an unexpected current to drive it into the wreck and for it to become entangled with no way of freeing itself.

Sounds like they have found debris in the search area around the titanic site - sounds like catastrophic failure?

Or... they've allegedly found debris, when you realise rescue is impossible and you've just hours left, would you cause the sub to implode for an instant demise. 

It allegedly descends until it lands on the bottom, then they have to self locate themselves. One big rock or titanic debris sticking up could be lethal? 

Would it even be feasible to make that happen?

Strange how they didn’t hear it implode though if that’s what’s happened

Cant see it being feasible unless they took down a jackhammer or some plastic explosives just in case.

Seems to be the case from this video (9.04)

https://www.youtube.com/watch?v=RAncVNaw5N0&t=547s

This isn't how it works with pressure vessels, which this basically is.  They might have a design pressure of X and is tested to a level above this (1.5 for ASME B31) and to actually fail the vessel catastrophically you have to go over 3x the yield stress, but there's no way you'd go over the rated design pressure intentionally in an industrial situation.  Especially when the consequences of failure is 5 dead people.

I did read that the operators didn't want to have this vessel "classified" by the likes of DNV, ABS, etc. , as all commercial vessels are, as it would take too long.

Debris has been identified as specific items "landing frame" and "rear cover" from the submarine.

Pedant alert, B31 is the Piping Code, pressure vessels are ASME BPVC, but not sure it covers subs!

Who would hear it and how?

US Navy will have hydrophones permanently operating I would have thought, just to monitor for any nefarious goings on. Sound travels a long way in water.

I'm no expert, but from what I've read over the past few days I've read a few comments stating that implosion would likely have been detected. Here's one quote from the Guardian

"Sound travels particularly well underwater,” Allum said. “A catastrophic implosion could be heard for thousands of miles and could be recorded. An implosion would likely trigger signals in military hydrophones, devices used for recording or listening to underwater sounds."

Could be totally nonsense, I've no idea, just what I've read recently. I can't find the article but I read one the other day about another sub that had imploded, and the sound of the implosion was detected hundreds (possibly thousands, I can't remember) miles away. A long way away anyway.

EDIT This is not the article I read the other day, but in this instance a Soviet sub that imploded in the Pacific in 1967, and the US Sound Surveillance System detected it hundreds of miles away, and were able to triangulate it's position in 5000m of water. I'd guess the Sound Surveillance System used in the sixties has since been replaced by much more advanced sensors by now.

https://en.wikipedia.org/wiki/Soviet_submarine_K-129_(1960)#Sinking

When the USS Thresher imploded, that was also picked up by the sound surveillance system

If they are listening for a sound about 1 ms long then maybe, but most likely ignored or missed.

Yeah I can see why it could be missed or ignored initially, but I would have thought that once this became public, they would have been checking to see if anything was detected. But who knows. 

If they heard something, and they probably did, they wouldn't release the information publicly.  A quiet word behind the scenes perhaps, but nothing else.

T.

Yeah good point, I guess whatever systems they now use must be highly classified

Now confirmed dead due to catastrophic failure.

Supporting the quiet word behind the scenes hypothesis is that the ROV didn't have to be on location very long before making unfortunate discoveries.

Very sad.  

T.

Plus plenty navys and air forces drop sonar bouys, which then process information and relay it by conventional means from the sea surface upwards. The RAFs Poseidon and before that Nimrods were equipped for this role. 

I suspect the hydrophone arrays, sonar buoys and ship/submarine hydrophones aren't reliant on a bloke and a set of headphones actually listening for a sound.

If they can identify specific vessels at large distances due to unique cavitation noises and squeaky bearings there's a lot of sound analysis and processing going on.

Yes, but a fellow agency can request them to look back through their data at specific timelines, this happens for airbourne stuff too with sentry aircraft over europe. Or, if you think something like an aircraft has hit the ground you can ask geological institutes to check for any anomalies in seismic data from extremely sensitive equipment. There are so many different scientific bodies listening and looking for different things, it's surprising what they pick up by accident. 

Yeah, there's a bit more tech now than what Sean had sailing in Red October.

Day to day yes but if something odd happens they can assign several blokes with headsets to go and listen to the records dating from the last communication.

When the ARA San Juan whilst they dont say they used said blokes they did search the hydrophone recordings in the relevant area and picked up the sound of it imploding and a rough location.

I guess question though is whether a small sub would get picked up and, if it was, whether the US would officially admit to it. With the San Juan it was an international system used for monitoring potential nuclear tests and so not overly secretive.

A short high energy impulse like that is very easily picked up via automated signal analysis techniques. In fact I would imagine Navy technology would be listening for precisely that sort of thing e.g. nasty stuff like torpedoes or missiles getting launched.

Wall Street journal now reporting that the navy did indeed pick up the sound of an implosion at the time it lost comms.

Indeed.

I can imagine the dilemma of deciding whether to let the families know this information; I suppose a 'miracle' survival would have been better than the prolonged agony of uncertainty.

Said on the news that they heard a noise that could have been an implosion.

I know next to nothing about sonar/acoustics but they also 'heard' regular knockings. In an ocean full of sounds from natural and man-made sources it must be very difficult to differentiate a single short signal from the others. At least it would appear that the end was mercifully quick rather than the lingering horror of suffocation in a claustrophobic nightmare.

Apparently an implosion would have been the equivalent to 50kg of TNT so I suspect they were pretty confident what the detected sound was.

But you need to be certain and hope is a powerful thing.

I heard on an earlier sub, a partner refused to work with OceanGate as Carbon fibre fatigues after cycling pressure and degrades with time. So I suspect carbon fibre will be the focus of the investigation.

And yet isn't carbon fibre used extensively in the aircraft industry where fatigue is also a critical concern?

The same source (Scott Manley) mentioned that there's been a lot of testing of carbon fibre in tension, but not compression.

Also, planes don't really have that much pressure difference on them. A little over half an atmosphere maybe.

Yeah I’ve now read that they did hear it. But for obvious reasons no detail on when and where 

You've reminded me of an interesting and unexpected catastrophic failure associated with carbon fibre that was found while I was working at BAe in the 80s.   The Harrier 2 (produced where I worked) was a very different aircraft from the original with a new power plant obviating the need for a water tank for injection into the turbine blades that meant hover duration was limited to the time that water was available.

One of the upgrades was carbon fibre wings replacing metal skin.   Survivability tests were carried out on the effects of ground fire (cannon shells) on the new wing and some dismay was caused by an unexpected effect caused by the combination of very strong carbon fibre skin and the wing being used as a fuel tank.  The shock waves from rounds hitting the wings and travelling through the fuel (which would have punched  holes in a metal wing) caused the entire wing surface to "burst" from the frame removing the wing surface rather than just a punctured wing.

Titan was towed out to sea behind that support vessel on the floating platform you can see it on in multiple pictures. I can only imagine the rough ride that must be going 100's of miles out into the mid Atlantic in all sorts of conditions. The chances of damage to the CF cylinder from knocks could be important?

Also, I doubt (don't know) that the Titan was stripped down, checked and tested after each trip for any stress damage. Probably the obvious parts were, but the actual hull...?

But it isn't an industrial pressure vessel, it's an experimental submarine. There are some mechanical similarities. Whether or not it should have been experimental vs certified given its role is another matter. I'm in two minds and I'm not going to get on my high horse about it in large part because I don't know how well this was understood by those aboard though it doe sound like it wasn't glossed over. I regularly fly paying guests exposing them, and myself, to significantly higher (but still acceptable to me) risk than other familiar forms of aviation. Their choice to join me is carefully informed (how well people understand risk is another conversation) and it is almost always accepted for the reward of an unusual experience.

Clearly, given what's happened, it's a fool's errand to argue this sub was safe but that wasn't my intent. My point is there's potentially a lot of space between 'safe', something well quantified with large margins, something functional with reduced yet adequate margins for its role, something 'unsafe' just waiting to fail and something dysfunctional that fails its first test. For example, if your pressure hull design has a margin of say 1.5 between design depth and crush depth, perhaps because you know it'll be operated where it can't reach crush depth and you accept the reduced margin for increased volume or reduced cost then the merit in having individual components with significantly bigger margin than 1.5x is reduced. It's not eliminated since parts do interact of course and where individual parts could trigger catastrophic failure, risks multiply.

Which is looking like a poor choice in hindsight. Whether or not I approve I can see why people might choose to do things differently, to accept more risk, lower margins, for a bigger reward. When you're doing something new it is of course very hard to fully quantify the risk, you don't know what you don't know and that is where a really thorough evaluation and testing and program comes in. I'm sure at least some involved thought they'd been through that process, others clearly disagreed.

This is a climbing forum we all choose to take significant risks (debatable how well understood) for the reward. Even something at the safer end of the game like sport climbing, we'll often use the same parts as industry for our anchors but for cost and convenience we expect and usually find less stringent practices around installation, maintenance and use than would and should be acceptable in a workplace. You could argue a 'bolt' is an industrial anchor like an experimental sub is a 'pressure vessel' and it is but also critically, it isn't.

jk

Separate point (that many have made): why on earth ... or rather in the very deep sea ... was the sub not spherical but cylindrical?

To fit more people into it using the same size spheres.

I guess you could just make the titanium spheres bigger but that would likely cost more.

What I don't understand is why they don't just use steel. It's a heavy resilient material which sounds perfect for submarines.

It won't be people 'listening' to the likely hundreds of inputs available from around the north Atlantic, in the first instance it'll be machines. These networks exist to detect, identify and triangulate sub-sea sounds of military interest. While it might not trigger the same level of alert/report as a rocket or torpedo launch an implosion would carry very well and is likely of significant enough interest to be flagged to a human in near real time.

Sounds from today's reporting like the event was detected and recognised by the US Navy at the time but that has, perhaps reasonably, been kept under wraps until visually confirmed.

jk

More space for passengers.

Might be wrong but I believe all comparable vessels have used spherical pressure hulls, but they only have space for between 1 and 3 people and are very cramped.

Buoyancy.

I'd prefer to be cramped than crushed to nothingness in a fraction of a millisecond.

Talking of the sickening double standards with regards migrants and rescuing, who recalls this:

https://www.theguardian.com/world/2019/jul/05/captain-who-rescued-42-migran...

Oh I don't know.  There are worse ways to die.

If the thickness of a steel sub suitable for that depth is such that the relative density is greater than 1.0, then a cost affective approach would have been to add incompressible floats to the top of the sub to make it buoyant. These are low tech and cheap.

I'm not pretending that there aren't going to be many issues with this approach that I'm not thinking of. There always are. But in my experience, starting simple is usually best.

It's worth remembering the shape wasn't necessarily the problem.

A pill can be made as resilient as a sphere, it'll have thicker walls for the same performance but it may have a better practicality/volume or cost/volume ratio. Practical spherical subs are compromised by their openings and construction, it's not a case of flawed shape vs perfect shape.

jk

Depend what you're building. If it genuinely is an experimental vessel to trial new materials and advance understanding then there always will be an element of uncertainty and possible unknown failure modes. We wouldn't have what are now common, safe systems without people taking significant, but what they believed to be manageable risks in the past. 
 

However if you're building a pleasure craft for tourists…

Very true. I don't think there are many spherical nuclear subs, and some of them may have very deep crush depths.

My thoughts exactly.

The reported banging was just noise, literally noise in the ocean and noise in the media.  It couldn’t be confirmed it was from the sub unless it was rescued and the occupants confirmed they made the noise.

At the time stamp of losing contact with the sub, a matching time stamp implosion noise had been recorded. This could only be confirmed once eyes were on the wreckage and now they have.

Very sad conclusion all round, particularly for the families who won’t have a body to bury.

Perhaps this will end the ghoulish fascination of titanic tourists, the site is after all a mass grave. Maybe all those resources could be better used elsewhere in the oceans for research and exploration. If only all the migrants recently lost at sea got better media coverage and support. Like I said, very sad all round. 

One could argue that not needing additional buoyancy which can be damaged, lost or snagged is simpler and safer. Also that buoyancy is big and heavy and fragile and probably also flammable once you haul it back onto deck.

The main benefit I can see of steel over Ti is material cost and availability of manufacturers rather than performance. That's presumably also what drove the novel choice of CF wrapping over solid Ti for the mid section.

jk

Of course, but this should be tested in a lab. If you want your sub to survive 300 cycles for example, then simulate 1000 cycles and see what happens.

Now maybe they did this. I don't know. Or maybe they carried out tests that didn't quite reflect the final solution. I'm all for finding new and better ways of doing things, but it should be fully tested as much as reasonable possible. And I'm not fully clear that the materials used where better than a simple approach. More exotic yes, but better?

I know the reasons are completely different, but Space X ditched carbon fibre which on paper seemed like the best material to use, but in practice the heavier stainless steel meant cheaper and more reliable launches (or more specifically re-entries).

Submersible that went to the bottom of challenger deep in the Mariana Trench. 
 

“The designed operational maximum dive depth of 11,000 m represents approximate full ocean depth. Test pressure of 14,000 msw provides a safety margin.[2] The vessel has been certified to a preliminary maximum diving depth of 10925 +-6.5 m by DNV, based on data from the deepest dive.[1] The vessel is commercially rated for repeated dives to full ocean depth.”

https://en.m.wikipedia.org/wiki/DSV_Limiting_Factor

What does better mean though? Better quantified, more affordable, more accessible, more workable, higher strength/weight or, better cycle life? There's always compromise.

If you just want stronger, you can just make it thicker whatever the material but then that inevitably causes compromises elsewhere.

Carbon fibres and composites are absolutely incredible but only when used carefully in very specific ways. I'm fascinated that anyone decided carbon filament wrapping a pressure hull was a worthwhile use of the material or budget, it superficially seems so counterintuitive. That's not intended as criticism, I'm sure there were reasons and it may not have been the cause of the loss.

jk

It looks like it was experimental mainly to avoid the rigours (and likely failure) of certification.

I think deep ocean is the only place for testing. I doubt anybody has built a 400 bar pressure vessel big enough to hold the sub. 

Cameron doesn't rate composites for that application. I tend to agree.

youtube.com/watch?v=qqm4NsMXEyA&

I'm surprised it works (worked?) and was worthwhile. I don't understand the choice but I also don't know what I don't know, my interest in and knowledge of composites is no more than recreational.

jk

You may be right. But I expect it can be scaled down for the test. 

Whether that gives you a reliable result however.

The other way would be to take it to deep sea on a crane, and plunge it 1000 times. It would be very time consuming and expensive, but at least it would be safe.

Almost all of the above.

Steel beats most materials when it comes to reliability, fatigue resistance, workability, cost. List goes on.

This is why you will generally see bolts on light weight car suspension still using steel where fatigue is likely the most important factor. Strength/weight less so, because you can always compensate with a larger diameter and take a small weight penalty.

They go nowhere near these kinds of depths. They only need to evade detection so there's no real reason to go really deep.

The deepest diving nuclear sub with conventional pressure hull that I know of is was the US NR1, which could go to about 900m

https://en.m.wikipedia.org/wiki/American_submarine_NR-1

There's a Russian nuclear sub that can go deeper, but the pressure hull is made from several spheres connected together.

https://en.m.wikipedia.org/wiki/Russian_submarine_Losharik

As I said upthread, all other DSVs that I'm aware of at least that can go down several Km use spherical pressure hulls. Not that you can't made a cylindrical hull to go deeper, it's just that the downside evidently outweigh the benefit of increased volume, unless of course you want to take passengers.

There's a 240bar hyperbaric chamber in Pickering that might just fit it. Pretty sure there are 400 bar chambers as the oil industry is going deeper and requires this pressure to test their kit.

This is what I struggle with. I can't imagine any of these paying clients to be anything other than extremely clever people who got to where they were partly by having a very clear understanding of the potential consequences (risk) of every decision they made. People like that don't get decisions made for them and they don't accept, "Yes it's fine," as an explanation to a serious question. It's also very difficult to imagine that they'd be easily duped by some fly-by-night submarine tour operator.

Returning to the OP's valid point and without dismissing the personal tragedy for the Titan victims and their families, how much closer to Katy Hopkins' "Show me dead photogenic children, I don't care," are we as a society given the contrast in reporting and public interest between four adventurers (them being wealthy is irrelevant) and hundreds of ordinary but desperate people including their kids drowning? Extremely depressing.

This is an unusual case so gets more media attention.

I know it sounds terrible, and it is, but people crossing the channel and dying is unfortunately a regular event.

Not to mention there's a semi fame element to this that always gets more attention.

Had a billionaire drowned when on holiday falling out of a inflatable boat, it wouldn't have got anywhere near the same coverage.

Hmmm ... not sure 1x of UKC's better threads.  A debate about who is more or less deserving to be saved from the ocean ... when in the end they all died.  Not our best side.  Interestingly not how UKC typically deals with a death in the mountains involving mountain rescue where we usually go to great lengths not to have morbid speculative chat threads.  Anyhoo ... 

I had a conversation with Mrs StuPoo2 while this was taking place.  She started by making a very similar point  ... "ugh .. just disgusting that these people could have spent so much money on this stupid endeavor.  Imagine what could have been done with that money if it had been put to a better cause!  And then imagine the cost of all the resources spent trying to save them!  Ridiculous!"

I have much sympathy with this line of thought.

However ... I reflected on my own experience.  I am a an avid user of our outdoor environment.  I go to the mountains, I paddle the rivers.  I spend more than is an appropriate amount of money on these endeavors and that money could undoubtedly be spent in other ways on planet earth to benefit others.  One day I will make a mistake and I will need help.  

How am I/how are any of us on these forums any different from these individuals?  We spend significant sums of money on these games, that money could be spent much more fruitfully and we need saving from time to time.  What's different?

I put it back to Mrs StuPoo2 that she wasn't actually upset with these people spending money on going 3800m deep (not the wisest decision IMO), or that they sadly got themselves into trouble people tried to help.  I suggested that she is instead disgusted by the existence of billionaires generally.

I don't think the fact that people spent money on a hobby or got into trouble are factors in our responses to this.  The strength of feeling is coming from the fact that they were billionaires and its fairly sickening that in todays day and age we allow a billionaire to exist.  Now - I'm not saying we shouldn't allow people to make and keep their own money ... I am 100% a capitalist.  I am suggesting that there is an extreme that capitalism creates, billionaires, that we could probably do without.

My sympathies to all who have passed away.

some construction details here mentions composite used 'to forgo the use — and the significant expense — of syntactic foam on its exterior'

https://www.compositesworld.com/articles/composite-submersibles-under-press...