Why did the Titanic tour submarine implode?

you are offensive

the word used was may

 

Another good article that delves into earlier discussion here about taxpayers funding.

I'm not sure I agree with Hall a bit. These people are paid either sitting at a desk or in the field looking at the sub..but I get his point about the CG investigating something they don't regulate. It does seem disconnected.

...do whatever you like and we'll pick up the mess...

NTSB Joins Investigation Into Titan Submersible Implosion | Law Commentary https://www.lawcommentary.com/articles/ntsb-joins-investigation-into-titan-submersible-implosion

 

Alan,
We have seen good sailing hull structures with only semi longitudinal unidirectionals at +/- 15 degrees to CL.

Assuming semi fixed ends, the sub tube would fail at the midpoint, at the cumulation of the compression and hoop loads?

So some not quite zero and some 90 might be a cautionary answer; but using only 40% of the theoretical properties!!

About the contained voids, not sure but best practice is only 4 atm autoclave?

 

Very interesting patent....

 

Thanks AJB for the precision, with which I mostly agree. I may add that there are, however, some specific parts which require a precise fiber placement ; in the case you wish to limite the weight of these parts. Rudder & daggerboard stocks, mast pillars, mast tubes (wing masts), for instance...

 

Ok, I will admit to a bit of "Nelson's Blood" to "steady the hand" before I wrote this.....So YMMV....

As many who have been on this forum for decades, you know there is a thread titled "In 10 years?"...started back in 2002. As close to the original IBM Intel 8088 PC as we are to the Intel Core i9-13980HX today

One of the rivers of this thread has been that computer programs have been diluting the ..."wisdom?''... "intuition?"... of engineers. Are people without significant experience turning to programs (maybe even AI in the last few years) to solve their proposed problems without even understanding the background, shortcuts, and issues of the programs themselves? An example is the old MSC NASTRAN program circa 1971 . Most engineers "of a certain age" will remember when their professors demonstrated the Euler Buckling analysis issue. Remember that computers are not accurate, but precise. So a "precisely" loaded column would not buckle, regardless of end fixity. This was demonstrated at the time (or at least to me in 1979).

In the loss of the TRITON, I have interacted with many DSSP engineers I respect, both on and mostly off these forums, who are plainly confused why "anyone" would proceed with the design and operation. Perhaps we are back to the Euler Buckling analysis issue...perhaps back to the reason why shop class is no longer offered in many US schools. The tools can cut and kill if you are unwary.

Perhaps it is time to bring shop back to school.


In 10 years?? https://www.boatdesign.net/threads/in-10-years.625/

 

JEH

I think it is a 2 fold issue.

1. Rapid proliferation of using software for “tasks” that previously required on the job training experience and knowledge to perform, and where such calculations were ostensibly by hand too. As such they have become “user” friendly to the point, no one questions the output – the computer says so. Again lacking the prerequisite knowledge to interrogate such output, ergo, it must be right, computer says so.

And the second part of this bit, is that 10 years experience takes - yup - 10 years. Yet in today's world of Google and all things high speed internet, everyone wants the answer in 10 seconds from a Google search, and not wishing to go through the learning curve. They want the answer and want it now!

2. Two words – professionalism and ethics.
One can teach it or simply be part of ones DNA. But if one wishes to ignore either or both, for the sake of ego or pride, or financial gain or these days – click bait social media “fame” - there is no legislation that can protect or counter this.

 

Stability and buckling are quite complex phenomena.

 

Suppose that this sub had been used for what many tourist subs are used for: exploring shallow reefs without scuba gear. Say, going down to 130 feet or less, which one source says is a typical limit for recreational divers without more specialized training and gear?

Is there any reason, properly maintained, it couldn't have achieved a reasonable safety margin, and dived many thousands of times?

In other words, does the failure of the Triton prove that all composite material (e.g., carbon fiber and epoxy) submarines are very unsafe, and should never be used, or instead merely show that this particular sub wasn't, for one reason or another, capable of safely going to the depths it was used at?

How typical is it for other tourist submarines to be made of composite materials?

E.g., I gather there are a number of flooded "wet subs" - that are used while wearing standard scuba gear (meaning air tanks, regulators and face masks), which presumably aren't used below the depths that people dive in standard scuba gear. Are some of them made of composite materials, and do some enclose the mechanical and electrical components that can't get too wet inside composite containers?

And fiberglass "narco-subs" have supposedly been used to smuggle drugs, but drug smuggling is already a pretty risky business, and the cartels that run them might accept some losses of subs, cargo and crew.

 

If true...this is interesting transcript of the trip:

 

IF that is a true transcript I can already see what the finding is. Since this was a FBW system (and I have no idea what feedback is given...so I'm not sure if the vertical thrusters where running all the time, but it seems that they flatted the A bank pretty quickly), that unconfirmed transcript really makes it look like they sunk out due to weight. I would have expected one or more trim stops, especially as this vehicle is so heavily biased around weight.

Also it is important to remember that there is no such thing as a "depth" gauge. It is a pressure gauge. Without additional sensors (CTD, XBT, SVP) a "depth" gauge is only a rough estimate.

 

Ok, where to start...

First, let us divide submersibles into two groups: free flooding (FF) and one atmosphere (1-ATM).

Second, notice I did not say submarine. A submarine is a fully contained vessel that can make long/ocean transits and submerge to a given depth without support while maintaining a one atmosphere interior. Most tourist submarines (let us draw the starting line at 1964's AUGUSTE PICCARD ) are built and constructed like military submarines have been for the last century. They are very conservatively designed and are steel as there is no need to go descend deeper than AUGUSTE PICCARD (PX-8); i.e. the fish and coral most tourists want to look at is realistically very shallow in the daylight zone. Additionally, at these depths there is absolutely no advantage to composite pressure hulls (i.e. the buoyancy of a steel pressure hull designed to let us say 300 FSW, is still positive), which is why composites are never used, even setting aside the better quality and NDT factors of steel. However, composite is often used for the non-pressure hull (i.e. free flooding) fairings, because of its higher buoyancy to weight ratio.

A submersible on the other hand, is a "smallish" vehicle that needs the support of a mother ship to maintain it; i.e. charge batteries, charge air banks, feed the crew, etc. Submersibles range from the 1937's FNRS-2 (1-ATM) to 1940's "Maiale" (FF) to 1960's SDV Mk VII (FF) to 2020's DCS (1-ATM). Submersibles can also be divided into two depth ranges, swimmer delivery vehicles ("Maiale", SDV, ASDS, DCS, etc) and "deep submergence" (FNRS-2, TRIESTE, ALVIN, MIR, TRITON, etc). Free flooding vehicles have their own issues, but generally pressure volumes are not one of them. In the case for free flooding subs, the majority of the structure can be made of composite as long as quality requirements are adhered to. Deep Submergence vehicles, on the other hand, need rigorous testing and materials that always provide positive buoyancy at extreme depths. This rules out many materials that compress volumetrically at depth. A 72 inch in diameter Titanium sphere squeezes about an inch radially at full submergence....that lost buoyancy must be made up by other methods as well as increased water density at depth. While I could go for a long time about this, I suggest you read SNAME's work Submersible Vehicle Systems Design ( Submersible Vehicle Systems Design | SNAME https://www.sname.org/submersible-vehicle-systems-design ) if you need a full account.

Finally, most "narco-subs" are actually "semi-submersibles" and are just low- freeboard, low-observable motor boats; a totally different thing.

 

How does the sensors, thrusters and peripherals communicate to the person inside the hull? One YouTuber claims he saw wires penetrating the back dome. Is there any seal that will be effective at 6,600 psi?

 

Here is one I kept for the fun of it. Starts at 1:08 and 45:40, whew. Like a 4 year old boy teaching a Naval Architect how to design a ship. Calls the blog Forensic Engineering and Failure Analysis. Said "I don't know" many times I lost track.

 

Yes, there are hull penetrators that are good to 20,000+ psi, and have been since the mid 1950's. The DSSP has used thousands of them from its inception after the loss of the USS THRESHER (SSN 593), usually made by D G O'Brien (now Teledyne DGO). A 6,600 psi one is an off the shelf item for electrical or FO. A penetrator is not the first place I'd look for a failure.

DGO Standard Products Catalog - Teledyne D.G.O'Brien - PDF Catalogs | Documentation | Boating Brochures https://pdf.nauticexpo.com/pdf/teledyne-dgo-brien/dgo-standard-products-catalog/40204-106933.html