Missing Titanic tourist sub

[kerbiloid]

4 minutes ago, lajoswinkler said:

It is the pressure vessel. 12.7 cm thick layer. Fiber "reinforces" epoxy resin. I've put reinforces in quotation marks because it played minor role in strengthening the structure against outside pressure, despite what Stockton Rush was saying. Thick epoxy resin was holding back bulk of the force.

If put a scratch, it weakens.

[kerbiloid]

I-obviouisly-dk if it's true. But doesn't sound exotically.

They say, it's the last conversation, but its source isn't given.

https://pikabu.ru/story/transkript_peregovorov_utonuvshego_batiskafa_i_neskolko_fotografiy_10454608?cid=278466113

[tater]

Yeah, I head an interview with a guy who went down on one of the earlier dives in Titan and he said it made banging/cracking noises (and it was not a Titanic dive I think, but a lower test dive). If true, they never should have taken it down again.

[DDE]

14 hours ago, tater said:

Yeah, I head an interview with a guy who went down on one of the earlier dives in Titan and he said it made banging/cracking noises (and it was not a Titanic dive I think, but a lower test dive). If true, they never should have taken it down again.

Granted, such noises are not entirely abnormal for a submarine. Modern military subs are built to avoid the constant creaking of WWII examples, but they still make a noise every now and then as they contract.

[DDE]

Maybe I'm late to the oarty, but here are two questions. (1) What could have bogged their ascent  even after jettisoning absolutely everything (at least ostensibly), and (2) how does composite fatigue work so that the failure occurs in the way up and not at peak depth?

[kerbiloid]

(3) Of course, we're excluding a sabotage.

[Jacke]

2 hours ago, DDE said:

Maybe I'm late to the oarty, but here are two questions. (1) What could have bogged their ascent  even after jettisoning absolutely everything (at least ostensibly), and (2) how does composite fatigue work so that the failure occurs in the way up and not at peak depth?

Everything I've read and watched says carbon composites are bad in compression.  And the failure isn't due to exceeding a compressive limit but the point at which the hull buckles in some manner.  There is also very little if any indication of the failure before it fails.  It's likely they were just going through their dive when the hull failed and destroyed the submersible.

[DDE]

3 hours ago, kerbiloid said:

(3) Of course, we're excluding a sabotage.

(4) Of course, we're assuming the disaster happened. Lotta defense and defense-adjacent types dying mysterious deaths these days.

[magnemoe]

9 hours ago, DDE said:

Maybe I'm late to the oarty, but here are two questions. (1) What could have bogged their ascent  even after jettisoning absolutely everything (at least ostensibly), and (2) how does composite fatigue work so that the failure occurs in the way up and not at peak depth?

Some theories is that snapping noises increased in frequency so they started dropping ballast to go up.  But it was already far to late. 
The WW 1 and 2 submarines was mostly riveted so you would get noise then the riveted joins shifted during decent or accent.  Modern are welded so you do not get this but the hull is compressed a bit 
With carbon fiber the cracks is the structure weakening so you get the something is very wrong, abort then it continue getting worse. 

[kerbiloid]

29 minutes ago, magnemoe said:

Some theories is that snapping noises increased in frequency so they started dropping ballast to go up.

 

Spoiler

 

 

[tater]

It's not "hit max depth, implode" but an issue of continuous degeneration with time at depth, plus cycle issues (flexing dissimilar materials in the composite, glue to domes, etc).

The issue of why the sub was not rising is interesting (assuming the leaked comms are accurate, they dumped ballast and only rose ~40m in a few minutes). Had they lowered pressure faster by rising faster (~1 atm every 10m), they might have survived, or possibly the flexing might have in fact made it worse (than at the start of crackling noises, obviously not worse than what actually happened), and it still implodes, but at a shallower depth (though still deep).

[Lisias]

20 hours ago, Jacke said:

Everything I've read and watched says carbon composites are bad in compression.  And the failure isn't due to exceeding a compressive limit but the point at which the hull buckles in some manner.  There is also very little if any indication of the failure before it fails.  It's likely they were just going through their dive when the hull failed and destroyed the submersible.

Everything I had read 10 years ago were predicting that Falcon9 would never be able to be reusable on an economical way…

That's the problem: we aren't material engineers, so we need to rely on what people that (supposedly)  knows the subject has to say. But people lie, some of them without the slightest remorse.

One blatant lie about this matter is the Carbon Fibber acquired from Boeing being unfit to be used, what could bring liabilities to Boing for selling "rot material". What people don't get is that the shelf-life of a material is not what decides if the material is unsuited for use or not, but the sum of the shelf-life PLUS the useful life of the device that was made with it. If the Carbon Fibber is good for 20 years, it was stored for 6 and Boeing wants his plane to be fly worthy for 15 years, then that material is unfit for Boeing's airplanes, but it's fine to anything else those useful life is 14 years or less.

Additionally, it's worth to note that that submersible had dive 90 times. NINETY. News were noticing the thing as it was its 14th dive.

So, apparently, Carbon Fibber is not exactly unsuited for the task, it have a very small life span - perhaps 50 dives, 75 for unmanned dives - and then the hull should be considered unstable and only used for suicidal missions.

Another thing that may be a factor on this tragedy was exactly the use of Titanium on the semi-hemispheres of the main hull. Titanium, as any other metal, expands and contracts with the temperature while Carbon Fibber don't. Airbus is getting some heat on their A380 from Emirates exactly due this reason (the paint expands, the carbon fibber hull doesn't, and so we have delamination).

It was being cogitated that there should be remains of the Carbon Fibber hull on the Titanium semi-hemispheres, where both parts are bolted together, if the hull collapsed somewhere in the middle of the ship. Since there's any, some engineers think that the failure point was exactly where the Carbon Fibber is bolted on the Titanium, and this would had happened because the hull was taking a lot of heat from the Sun while being towed - the thing used to be carried onboard on a bigger ship, probably with better shielding from the Sun - and so the titanium heat dilatation would had fractured the Carbon Fibber, weakening the material prematurely.

Edited July 21, 2023 by Lisias
Tyops gallore!!

[razark]

52 minutes ago, Lisias said:

Additionally, it's worth to note that that submersible had dive 90 times. NINETY.

What depth did it reach on those dives?

89 dives to 5 meters and one dive to 5000m is not the same as 90 dives to 5000m.

 

Also, how many dives was it rated for?  Every trip is putting strain on the hull, and it's going to add up.

[Lisias]

1 hour ago, razark said:

Also, how many dives was it rated for?  Every trip is putting strain on the hull, and it's going to add up.

That's one of the few consensus I had read about it: there was only one vehicle, and not two or three to do the stress tests, like that one NASA did with the SLS fuel tank:

Spoiler

 

 

1 hour ago, razark said:

What depth did it reach on those dives?

89 dives to 5 meters and one dive to 5000m is not the same as 90 dives to 5000m.

Good question. I will dig about on the Week End and see what I find, 

[tater]

The vehicle had only dived to Titanic 2 times before I think? Other dives were substantially shallower.

 

This is a nicely done short vid on how it might have imploded (not technical details on where it failed, but a nice render):

 

[Lisias]

41 minutes ago, tater said:

The vehicle had only dived to Titanic 2 times before I think? Other dives were substantially shallower.

The information I have is that the Titan had 50 test drives on Marianas and pressure chambers, "including to depths similar to those of the Titanic". No figures for how many of each.

https://metro.co.uk/2023/06/22/how-many-times-has-the-titan-gone-to-the-titanic-and-how-deep-is-the-wreck-18994926/#:~:text=OceanGate has previously stated that,as in a pressure chamber.

So we have 50 test dives plus 90 "effective" dives, but only 13 of the later were really successful (i.e., reached the Titanic). Some were aborted early on the way, and in some they didn't found the Titanic (they reached the Titanic's depth on these ones, but far from the wreck and ended up using all the time trying to find the thing without success and aborted). And, of course, some where they aborted half way down due technical problems.

I think the only way to get real information is to find the dive logs of the vehicle, but I don't think this info is available at this moment.

Edited July 21, 2023 by Lisias
Better phrasing

[tater]

59 minutes ago, Lisias said:

I think the only way to get real information is to find the dive logs of the vehicle, but I don't think this info is available at this moment.

Yeah, It seems that the vehicle was refurbed or rebuilt after cracking noises in testing in the late tees, and the "new" version (whatever changes/fixes were done) only started diving in 2021.

One article I saw may have mixed the dives of the 2 Ocean Gate vehicles. One has a huge dome window—but operates at much shallower depths.

Guess they had 3 vehicles.

[tater]

What they needed to do to test this properly:

Dive cycle (unmanned) to destruction knowing that cyclic fatigue exists. From this they have a known value for when it might fail (though it might fail sooner on the next one, no way to tell). Since they claimed instrumentation to try and detect these problems, had they destructively tested, they would in fact have calibration data for those instruments. They'd know in retrospect that a certain pattern of readings might have predicted the failure—making those instruments actually useful.

 

[kerbiloid]

Why not test this in a diving chamber instead of real diving?

Spoiler

 

[magnemoe]

On 7/21/2023 at 9:28 AM, kerbiloid said:

Why not test this in a diving chamber instead of real diving?

  Hide contents

 

Pressure is way to high, you would need an chamber larger than the submarine and able to support the pressure so it would likely to be more expensive than the sub itself. 
Now idea is not stupid, pretty sure they use an pressure chamber to test robotic submersibles as they are much smaller and tend to not dive as deep. 

I assume the image is an pressure tank used by divers diving to 200 meter depth or similar. Divers goes down in an diving bell and the pressure chamber up on the ship is kept at this pressure so they can depressurize in relative comfort.  This is run by NASA and is not on a ship so probably some experiment.  Note the air lock at the right to pass items like food into the chamber. 

[Minmus Taster]

I'm gonna talk about the possible human remains found in the sub. I'll put it in a spoiler box since it will probably be upsetting to some;

Spoiler

DNA testing is being done on the remains found, no details of the condition of the remains were given obviously but we can infer based off some of what they said. I get the impression the remains are just a mass of viscera belonging to multiple people. Yikes.

 

 

[Nuke]

5 hours ago, Minmus Taster said:

I'm gonna talk about the possible human remains found in the sub. I'll put it in a spoiler box since it will probably be upsetting to some;

  Hide contents

DNA testing is being done on the remains found, no details of the condition of the remains were given obviously but we can infer based off some of what they said. I get the impression the remains are just a mass of viscera belonging to multiple people. Yikes.

 

 

Spoiler

the parts probibly had to be collected with a fine mesh strainer. 

 

[monophonic]

3 hours ago, Nuke said:

  Hide contents

the parts probibly had to be collected with a fine mesh strainer. 

 

Spoiler

I doubt the usefulness of testing DNA from such mixed mess. I think bone fragments are more likely.

 

[kerbiloid]

5 hours ago, monophonic said:

I doubt the usefulness of testing DNA from such mixed mess.

To ensure that nobody escaped survived by being late to the flight.

[DDE]

https://www.businessinsider.com/oceangate-cofounder-send-humans-live-venus-atmosphere-2050-titan-sohnlein-2023-7

OceanGate's cofounder wants to send 1,000 people to a floating colony on Venus by 2050, and says we shouldn't stop pushing the limits of innovation