Titanic tourist sub goes missing

[Ben]

I wondered that about the brittleness of the carbon fiber. I have very little knowledge other than from viewing images from a completely different application: carbon fiber arrows that shattered and did a number on the archer.

[dogmush]

https://web.archive.org/web/20230619165742/https://www.oceangate.com/our-subs/titan-submersible.html

Thanks, that's the blurb I was looking for.

Although:

Real-Time Health Monitoring
The most significant innovation is the proprietary real-time hull health monitoring (RTM) system. Titan is the only manned submersible to employ an integrated real-time health monitoring system. Utilizing co-located acoustic sensors and strain gauges throughout the pressure boundary, the RTM system makes it possible to analyze the effects of changing pressure on the vessel as the submersible dives deeper, and accurately assess the integrity of the structure. This onboard health analysis monitoring system provides early warning detection for the pilot with enough time to arrest the descent and safely return to surface.

Clearly not.

[230RN]

I wondered that about the brittleness of the carbon fiber. I have very little knowledge other than from viewing images from a completely different application: carbon fiber arrows that shattered and did a number on the archer.

I kinda wondered about that a little since I heard one expert say it was only about 28 or 29 degrees F down there.  Not bad, but under those repetitive dives/cycles, it makes you wonder.

Remember my remarks about how the pressure is like an absolute vacuum inside the vessel compared to the outside pressure, and my mentioning how large CRT picture tubes "ex"ploded when broken and throw high velocity glass all over.  And that was only a 14.7 psi pressure differential brtween inside the CRT tube and the air in the room.  This scattering  accounts for the dispersion of the pieces in an implosion.

Terry, 230RN

REF (TV picture tube broken by a thrown brick  The brick broke in half):
https://youtu.be/_kAxSaETJRI (2:23)

The tube implodes, but the pieces still go flying through the middle and out the other side.

Pressure ("vacuum") in a TV picture tube is usually around 2 X 10^-7psi. (0.0000002 psi)

 

[Northwoods]

Would this also apply to aircraft components, like the composite fuselage of the Boeing 787?  It is not seagoing, but there is pressure cycling during ascents and descents.

Yes

[WLJ]

Jeeze, I hope it wasn't my guns.



(Tasteless but irresistible joke... sorry!)

Doesn't bother me.
Already seen a bunch of memes but I'm holding off on posting them here for the moment.

[WLJ]

Titan submersible parts believed to be found among the debris
https://www.bbc.com/news/live/world-us-canada-65967464?ns_mchannel=social&ns_source=twitter&ns_campaign=bbc_live&ns_linkname=649489af523d5b12617081dc%26Titan%20submersible%20parts%20believed%20to%20be%20found%20among%20the%20debris%262023-06-22T17%3A51%3A07.758Z&ns_fee=0&pinned_post_locator=urn:asset:2ab74475-596d-498e-944a-9785095ffb60&pinned_post_asset_id=649489af523d5b12617081dc&pinned_post_type=share

[Hawkmoon]

I place almost zero stock in news reports of such occurrences. I’m going to concur in it imploded Sunday and going to postulate that the cheaped out on window is what did it. Utter stupidity to cheap out on such a vital aspect of the design.

The only references I have seen to the quality of the porthole have been in this thread. What was the deal on the window? Got any links to articles discussing it?

[dogmush]

The only references I have seen to the quality of the porthole have been in this thread. What was the deal on the window? Got any links to articles discussing it?

It comes from a 2018 Lawsuit between OceanGate and their former Director of Marine Operations

Article on sub here:  https://techcrunch.com/2023/06/20/a-whistleblower-raised-safety-concerns-about-oceangates-submersible-in-2018-then-he-was-fired/

Lawsuit here: https://storage.courtlistener.com/recap/gov.uscourts.wawd.262471/gov.uscourts.wawd.262471.7.0.pdf

From Page 12 of the lawsuit:

19. 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 the 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.

[Hawkmoon]

OceanGate claims in it's blurbs that the Titan had some kind of integrated hull health sensor system.  I'd be interested in an acedemic way on what that was and how it worked.

I tried to go to their website and get the exact verbage they used, but their site is down.

I saw an article discussing (and dismissing) this. They were apparently strain gauge sensors embedded throughout the composite. The conclusion of the article was that, by the time a sensor like that reported an out-of-spec reading, it would already be too late to do anything about it.

IMHO, it's another example of OceanGate's (which probably means Lockton's) hubris. Apparently he was sort of a whiz kid. The problem with that is that he may have decided that he knew better than the cumulative expertise of people who knew more than he did to begin with. That's what led to firing the operations director who didn't think the Titan was safe. Unfortunately, Lockton didn't put just himself at risk. He put up a web site that seems to have greatly embellished on the purported safety of the vessel, thereby putting his customers at risk.

Engineering always includes a factor of safety, and the factor of safety generally gets larger as the risks become greater. Dogmush has posted that a 5-inch thick tube hull "should" be strong enough for a depth of 13,000 feet -- and it was, for a few dives. But I wonder what the safety factor was in that design? How much of a safety factor would you want in the vessel taking you down to where the external pressure is thousands of atmospheres? Lockton, according to articles, liked to "innovate," which probably means pushing the envelope. My bet is that he didn't design in much of a safety factor.

[Hawkmoon]

"some kind of integrated hull health sensor system."

Taken from an XBox or a Play Station?

Length of clothesline rope stretched across the interior ...

[MechAg94]

I saw an article discussing (and dismissing) this. They were apparently strain gauge sensors embedded throughout the composite. The conclusion of the article was that, by the time a sensor like that reported an out-of-spec reading, it would already be too late to do anything about it.

IMHO, it's another example of OceanGate's (which probably means Lockton's) hubris. Apparently he was sort of a whiz kid. The problem with that is that he may have decided that he knew better than the cumulative expertise of people who knew more than he did to begin with. That's what led to firing the operations director who didn't think the Titan was safe. Unfortunately, Lockton didn't put just himself at risk. He put up a web site that seems to have greatly embellished on the purported safety of the vessel, thereby putting his customers at risk.

Engineering always includes a factor of safety, and the factor of safety generally gets larger as the risks become greater. Dogmush has posted that a 5-inch thick tube hull "should" be strong enough for a depth of 13,000 feet -- and it was, for a few dives. But I wonder what the safety factor was in that design? How much of a safety factor would you want in the vessel taking you down to where the external pressure is thousands of atmospheres? Lockton, according to articles, liked to "innovate," which probably means pushing the envelope. My bet is that he didn't design in much of a safety factor.

And on that last, how do you feel about the risk of a vessel where you are pushing down close to a single digit safety factor % (it might actually be more).  That is getting pretty tight.  Does the carbon fiber material accumulate damage or fatigue with each dive?  If so, I am sure it is cumulative.  Our tech is probably better at evaluating that with steel rather than composites, but that is outside my experience. 

[dogmush]

Engineering always includes a factor of safety, and the factor of safety generally gets larger as the risks become greater. Dogmush has posted that a 5-inch thick tube hull "should" be strong enough for a depth of 13,000 feet -- and it was, for a few dives. But I wonder what the safety factor was in that design? How much of a safety factor would you want in the vessel taking you down to where the external pressure is thousands of atmospheres? Lockton, according to articles, liked to "innovate," which probably means pushing the envelope. My bet is that he didn't design in much of a safety factor.

I don't disagree with your post, but since I amateur gunsmith, run vessels at sea, and generally build things I feel like I need to point out in my defense that "should be strong enough" is the back of envelope SWAG step that precedes researching the material, math, and testing, not the last step before hopping in the MF'er and setting sail.

[Boomhauer]

Would this also apply to aircraft components, like the composite fuselage of the Boeing 787?  It is not seagoing, but there is pressure cycling during ascents and descents.

In general all pressurized aircraft (to my knowledge) are subject to cycle limits on top of the component inspections whether they are traditional metal or composite construction.

[dogmush]

And on that last, how do you feel about the risk of a vessel where you are pushing down close to a single digit safety factor %.  That is getting pretty tight.  Does the carbon fiber material accumulate damage or fatigue with each dive?  If so, I am sure it is cumulative.  Our tech is probably better at evaluating that with steel rather than composites, but that is outside my experience.

It's outside my experience as well, but I note that Carbon Overwraped Pressure Vessels exist, and 414bar is available COTS, with custom 700bar vessels available, so it's within someone's experience.  Perhaps they were a 50 something white guy.

*Yes I know that internal pressure and strength in tension is not the same as external pressure and strength in compression, but still, these aren't exactly uncharted waters for industry, just OceanGate, apparantlly.

[WLJ]

OceanGate has issued a statement confirming all 5 are dead.

[BobR]

In general all pressurized aircraft (to my knowledge) are subject to cycle limits on top of the component inspections whether they are traditional metal or composite construction.

Aircraft lifespan is measured in pressurization cycles vs airframe hours for the most part. Each type has a limit for pressurization cycles and once it is hit that plane is scrapped. I am sure somewhere in there are inspection intervals to make sure they don't suddenly turn their airplane into a convertible ala Hawaiian Air. As I am only familiar with metal and rivets on aircraft I wonder how they go about inspecting composite aircraft for fuselage fatigue because AFAIK they are essentially glued together (sort of). I can see some reading in my future just because.

bob

[WLJ]

Debris was found 1,600 ft from the Titanic

OceanGate Expeditions has confirmed the deaths of the five men on the missing Titan submersible, parts of which were discovered today on the ocean floor, 500 meters from the bow of the famous ship they died trying to see.

The landing frame and rear cover of the missing submersible were discovered today by a remote operated submarine in a devastating blow to any hope that the men may still be found alive.

It would mean the sub suffered a crack and imploded under the underwater pressure, instantly killing all five men on board.

CNN reports that the two pieces of debris were found at 12,500ft underwater, 1,600ft from the famous shipwreck's bow

https://www.dailymail.co.uk/news/article-12223805/Debris-field-discovered-search-area-near-Titanic.html

[WLJ]

News conference has started

https://www.bbc.com/news/live/world-us-canada-65967464

[RocketMan]

Two separate debris fields found so far.  Debris confirmed catastrophic implosion failure of the pressure hull.  Families have been notified by the USCG.

[RoadKingLarry]

Debris confirmed catastrophic implosion failure of the pressure hull.

Called it.
Four *expletive deleted*ing idiots with more money than brains paid another *expletive deleted*ing idiot with enough hubris to cover the ocean so they could all ride to their death in a tinker toy, wannabe submarine.

[230RN]

Pressurized airliner cabins:

Air pressure at sea level, 14.7 psi

Air pressure at 30,000 feet, 5.57 psi

Difference is 9.18 psi cycling pressures. 

I believe they maintain cabin pressure at about 10,000 feet, or about 10 psi

The pressure hereabouts (Golden CO) is around 12 psi.

A far cry from differential pressure cycling in sea water at the surface and at the Titanic's depth.

[Hawkmoon]

I don't disagree with your post, but since I amateur gunsmith, run vessels at sea, and generally build things I feel like I need to point out in my defense that "should be strong enough" is the back of envelope SWAG step that precedes researching the material, math, and testing, not the last step before hopping in the MF'er and setting sail.

I do the same things (or did, when I was younger and my body hadn't betrayed me). It's one thing to tie a bunch of helium balloons to a lawn chair and go up by yourself. It takes a special kind of hubris to take something that multiple experts say isn't safe, declare that it's actually SO safe they just don't have the methods to test how safe it is, and take paying customers down 2+ miles under water.

https://www.theguardian.com/world/live/2023/jun/22/titanic-sub-live-updates-search-titan-missing-submarine-submersible-rescue-us-coast-guard-latest-news

An underwater researcher has said the search for the Titan shows the desperate need for more deep-sea technology in the US.

Nick Rotker, from the non-profit research and development company Mitre, said “more robust capability” was needed to be able to cover large areas of ocean.

Rotker said:

The issue is we don’t have a lot of capability or systems that can go to the depth this vessel was going to.

Or ... how about we just don't take paying customers two miles down in experimental pressure vessels?

[WLJ]

I do the same things (or did, when I was younger and my body hadn't betrayed me). It's one thing to tie a bunch of helium balloons to a lawn chair and go up by yourself. It takes a special kind of hubris to take something that multiple experts say isn't safe, declare that it's actually SO safe they just don't the methods to test how safe it is, and take paying customers down 2+ miles under water.

https://www.theguardian.com/world/live/2023/jun/22/titanic-sub-live-updates-search-titan-missing-submarine-submersible-rescue-us-coast-guard-latest-news

Or ... how about we just don't take paying customers two miles down in experimental pressure vessels?

There is some justice in the fact the CEO went down with it. *expletive deleted*ing sucks he took 4 others with him in the process.

[BobR]

Called it.
Four *expletive deleted*ing idiots with more money than brains paid another *expletive deleted*ing idiot with enough hubris to cover the ocean so they could all ride to their death in a tinker toy, wannabe submarine.

You and pretty much anyone else with a elementary understanding of water pressure and more than 6 neural pathways still functioning.

bob

[Hawkmoon]

Called it.
Four *expletive deleted*ing idiots with more money than brains paid another *expletive deleted*ing idiot with enough hubris to cover the ocean so they could all ride to their death in a tinker toy, wannabe submarine.

^^^ I concur.

The real mystery is why an expert like Nargeolet was willing to go down in the thing.