Titanic tourist sub missing

[smartcooky]

Well, it's just as well then that I never said it went inwards, innit?

I remind you of your own words

https://www.internationalskeptics.com/forums/showpost.php?p=14410631&postcount=1340

The only pieces that fly out are those that bounced on something else going inwards.​

Oops! Oh dear!!

 

[SpuriusMaximus]

There's no oops except your being unable to read my writing, what, 5 or 6 times, that it popped outwards since message #1346. Also how that can happen without overpressure inside. Including some messages you actually answered to without reading.

It wasn't even particularly hard to parse, since you're the only one who still has trouble with it.

Popping an "Oops! Oh dear!!" when it's you apparently being unable to read is just about the dumbest thing ever. Oooh, and red colour too. Like, what, did you need to seriously emphasize that you didn't even pause to read before rushing to ventilate your tonsils to hear yourself trying to sound smart? Making sure nobody missed your dumbassery? Actually flexing that you can't read?

Do I need to send you a link to some online speak-and-spell so you can finally learn how to read? Or?

Really, you should try reading sometime. It's amazing what kinds of stuff you can learn if you can read

 

[smartcooky]

There's no oops except your being unable to read my writing, what, 5 or 6 times, that it popped outwards since message #1346. Also how that can happen without overpressure inside. Including some messages you actually answered to without reading.

It wasn't even particularly hard to parse, since you're the only one who still has trouble with it.

Popping an "Oops! Oh dear!!" when it's you apparently being unable to read is just about the dumbest thing ever. Oooh, and red colour too. Like, what, did you need to seriously emphasize that you didn't even pause to read before rushing to ventilate your tonsils to hear yourself trying to sound smart? Making sure nobody missed your dumbassery? Actually flexing that you can't read?

Do I need to send you a link to some online speak-and-spell so you can finally learn how to read? Or?

Really, you should try reading sometime. It's amazing what kinds of stuff you can learn if you can read

I read your post perfectly well, and unless you have your own unique meanings for the words "in", "bounced" and "outwards", you were undeniably saying that the ONLY way something can go outwards in an implosion is if it is going inwards first, and bounces off something. There is NO other possible meaning to what you said. Maybe English is not your first language?

Also

"Also how that can happen without overpressure inside?"

Overpressure in an implosion can be caused by a rapid ingress of water under pressure, an ingress so fast that the air inside the vessel, which has nowhere to go, has less and less volume to be in, and since the amount of air remains the same and the volume decreases, two thing happen

1. The air pressure spikes
2. The temperature spikes

These are explained in Boyle's Law and Charles' Law

Boyle's Laws: The pressure, p, of a fixed mass of gas is inversely proportional to its volume, V, at constant temperature (i.e. p ∝ 1/V).

Charles's law: The volume, V, of a fixed mass of gas is proportional to its absolute temperature, T, at constant pressure (i.e. V ∝ T).

Reduce the volume of a sealed container of air and the pressure and temperature of the air will rise.

ETA: There is another possible cause for an overpressure event - cavitation. This is particularly relevant in the case of an implosion scenario not caused by a general hull failure (collapse) but by a large single point failing such as a hatch or a torpedo door. In those circumstances, the water rushes in so fast that it momentarily far exceeds the pressure of the water outside the vessel, and blows parts outwards... and that is what we see in Titan. We know now that the seal between the titanium dome and the cylindrical hull failed instantaneously, The forward titanium dome is blown outwards, completely separated from the carbon fibre hull by the violent impact of the surge of water under tons of pressure striking it at a few thousand kilometres per hour.

 

[SpuriusMaximus]

I read your post perfectly well, and unless you have your own unique meanings for the words "in", "bounced" and "outwards", you were undeniably saying that the ONLY way something can go outwards in an implosion is if it is going inwards first, and bounces off something. There is NO other possible meaning to what you said. Maybe English is not your first language?

That was about a CRT implosion used as an illustration for how pressure works. The domes obviously didn't implode. Only the composite tube in the middle did.

Reduce the volume of a sealed container of air and the pressure and temperature of the air will rise.

Except here it's the other way around. It's the pressure that causes the volume to reduce. It's not reduced to a given volume, but to whatever that pressure makes it reduce to. Not the least because it's not a sealed container any more, given the speed at which the cracks would propagate through that hull, which is like 6 times the speed of sound in water. The hull would no longer be sealed along any X coordinate along its length before the water got there. Essentially you just have an air bubble. The only thing constraining its volume is the pressure of the water around it.

Again, a CRT implosion is a good illustration. It's not the overpressure that makes the cracks propagate. The cracks go at the speed of sound in glass.

ETA: There is another possible cause for an overpressure event - cavitation. This is particularly relevant in the case of an implosion scenario not caused by a general hull failure (collapse) but by a large single point failing such as a hatch or a torpedo door. In those circumstances, the water rushes in so fast that it momentarily far exceeds the pressure of the water outside the vessel, and blows parts outwards... and that is what we see in Titan.

Except, again, that's not what we actually see on that camera. We don't see the hull spread all over the place, like in an explosion, we see it all bunched up into the middle and shoved into the rear dome.

And for the dome itself, it's a hemisphere. It's not the same scenario as a big sub and a small torpedo door. Here the "door" is the whole side of it. And it would start to tumble immediately to let that air out, if nothing else because the centre of mass is at R/2 while the centre of buoyancy is at 3R/8. And the fact that separation would have been only nearly instantaneous, but not perfectly instantaneous would also make it tumble as the water on some side would have a fraction of a millisecond head start. But even without that, there's not a whole lot to keep it in.

More importantly, see that rear dome again. Whatever overpressure might have built up there, obviously wasn't enough to keep the hull strips from being pushed into it by the outside pressure.

 

[Ziggurat]

Yes, well, watch some videos about its shape. It's a truncated cone. Well, a truncated spkere arc, but same idea. And yes, it was kept in place by 2.5 tons of water per square inch while that sub is in one piece, but exactly 0 once the pressure equalized.

There were fittings in place to keep the window secure even when pressure was equalized. They weren’t designed to withstand significantly higher internal pressure, but they absolutely would hold it in place when there was no pressure differential. It didn’t fall out each time the sub was raised to the surface. If those fittings broke, it’s because something applied force from the inside strong enough to break those fittings.

 

[Ziggurat]

Except here it's the other way around. It's the pressure that causes the volume to reduce. It's not reduced to a given volume, but to whatever that pressure makes it reduce to.

No. Pressure isn’t constant in this scenario because the momentum of the water is significant. It’s like putting a mass on top of a spring. Yeah, the equilibrium compression of the spring is just given by the weight, but if you drop the weight onto the spring, it’s going to compress beyond that. You will get to a point that the spring is applying more force to the mass than the weight of the mass.

The water is like a mass being dropped onto the spring of the air. The air starts at lower pressure, but it compresses PAST the ambient pressure of the water because the water flowing in has momentum. And then it will try to bounce back. It’s not an equilibrium situation.

 

[SpuriusMaximus]

There were fittings in place to keep the window secure even when pressure was equalized. They weren’t designed to withstand significantly higher internal pressure, but they absolutely would hold it in place when there was no pressure differential. It didn’t fall out each time the sub was raised to the surface. If those fittings broke, it’s because something applied force from the inside strong enough to break those fittings.

Which is just as easily explained by that end cap crashing into the carbon fibre hull, that was busy crushing towards the axis of the sub. Regardless of where that "spring" equalizes, the dome initially lost support all around, and the net force would initially push it hard towards the centre of the sub.

 

[smartcooky]

No. Pressure isn’t constant in this scenario because the momentum of the water is significant. It’s like putting a mass on top of a spring. Yeah, the equilibrium compression of the spring is just given by the weight, but if you drop the weight onto the spring, it’s going to compress beyond that. You will get to a point that the spring is applying more force to the mass than the weight of the mass.

The water is like a mass being dropped onto the spring of the air. The air starts at lower pressure, but it compresses PAST the ambient pressure of the water because the water flowing in has momentum. And then it will try to bounce back. It’s not an equilibrium situation.

Indeed!

Have a look at this video. This is Samuel Pence, a maritime historian with a very good understanding of ship's engineering principles.

I have cued to the important part

https://youtu.be/6FhIBvIezas?t=294

...but pay particular attention to what Samuel says from 6:18 onwards...

(Here is a transcript from 6:18 to 7:38 for those who don't watch videos)

Now that we have a pretty good idea of how this breach occurred, let's now try to figure out exactly where it happened on the forward or aft part of the sub. Well based on this underwater footage I think we figure out the answer. Do you see this titanium dome that was blasted out away from the rest of the sub and is just sitting by itself? Well this titanium dome is part of the forward titanium dome, you can just see a little bit of the viewport sticking out there. What we think happened was the water worked its way through the forward titanium ring and then when the breach happened this titanium dome was pushed out away from the rest of the sub by the rebound of the water rushing in then as the water came in it just began crushing and tearing apart everything within the sub. All of this wreckage you are now seeing on camera? This is part of the aft section of the Titan submersible. All of this debris that you see sticking out behind that titanium dome - that's the aft titanium dome and the aft titanium ring you see there? Well all of that is the carbon fiber that made up the hull - it was all pushed inward as the water forced its way in and caused the implosion and then all this carbon fiber was forced into the aft titanium dome and the aft titanium ring, which is why you see it squished and pushed in like it is here in the Titan sub's wreckage.
​

I'm guessing you will agree with most of this, and I expect some others will not.

 

[Ziggurat]

Which is just as easily explained by that end cap crashing into the carbon fibre hull

If it wasn’t over pressure from rebounding water/air that popped out the window, then it would need to be the actual hull remains impacting the window from inside. And if that happened, then those remains should be sticking through the window hole, not thrown clear.

 

[SpuriusMaximus]

They don't have to hit right dead centre and go through, to dislodge that thing, especially since most of the strips we see in the aft section are wider than that. Hitting a corner of one, especially since, as I was saying, I'd expect that dome to be starting to tumble, would be more than enough.

And, hell, even the dome suddenly unbuckling within half a millisecond would be a mighty enough kick in the other direction. That analogy of a weight on a spring also works when the spring is the titanium dome, that's pre-compressed to a couple thousand tons of force and suddenly let loose, and the weight is that window. I've had toy guns that worked on that principle.

 

[Ziggurat]

That analogy of a weight on a spring also works when the spring is the titanium dome, that's pre-compressed to a couple thousand tons of force and suddenly let loose, and the weight is that window.

No, that doesn't work. If the dome expands, that doesn't push the window out. The dome would need to contract, by a lot, to do that with any significant force. And the dome doesn't expand or contract enough in any case.

 

[Darat]

I was watching the footage, and I had a most visceral reaction when it dawned on me that what was pointed out to be the remains of the carbon fibre tube was also the remains of the people as well. Thank goodness it happened before they could know what was about to happen.

 

[jeremyp]

If it wasn’t over pressure from rebounding water/air that popped out the window, then it would need to be the actual hull remains impacting the window from inside. And if that happened, then those remains should be sticking through the window hole, not thrown clear.

Why?

If the window was hit on the inside by a piece of high speed carbon fibre, why would the carbon fibre necessarily stop at the window? There seemed to be a few bits strewn around the front dome.

I'm guessing* the, once the pressure inside and outside are in equilibrium, it wouldn't take much to pop the window. I don't know what caused it to pop and neither does anybody else on this board. I'm also not sure that the window popping out is significant enough to have a big argument about.

I'm not even sure the knowing the structure failed at the interface between the front ring and the carbon fibre is really all that important either. It would be if anybody was seriously proposing to build another submersible to a similar design, but I don't see that happening for a while.

The most important thing here is the human factors that led to the catastrophe and however deluded ********* like Stockton Rush can be prevented from killing people in the future.

*yes guessing, like everybody else here

 

[theprestige]

I thought the failure mode and progression were pretty obvious from the debris in the photos. Are you all seriously not seeing it?

 

[Ziggurat]

Why?

If the window was hit on the inside by a piece of high speed carbon fibre, why would the carbon fibre necessarily stop at the window?

It wouldn't. I think it would stick into the hole.

But it can't shoot all the way through the hole and have the other end still stuck on the other dome.

I'm guessing* the, once the pressure inside and outside are in equilibrium, it wouldn't take much to pop the window.

When the hull collapses, the pressure doesn't just equalize, it overshoots before equalizing. The question is where the collapse originated. If it originated in the middle, then we should expect the carbon section to be split with parts shoved into both dome sections. If it originated in the back, the carbon should be shoved into the front. And if it originated in the front, the carbon should be shoved into the back. That's what we see.

The window popping out tells that the window isn't what failed.

 

[jimbob]

It wouldn't. I think it would stick into the hole.

But it can't shoot all the way through the hole and have the other end still stuck on the other dome.



When the hull collapses, the pressure doesn't just equalize, it overshoots before equalizing. The question is where the collapse originated. If it originated in the middle, then we should expect the carbon section to be split with parts shoved into both dome sections. If it originated in the back, the carbon should be shoved into the front. And if it originated in the front, the carbon should be shoved into the back. That's what we see.
The window popping out tells that the window isn't what failed.

Yup.

As an aside I wonder what pressure the bubble initially compressed to. I guess the water rushing in from all directions would have caused a transient pressure far above the local water pressure.

 

[Jack by the hedge]

Wouldn't just be the water that was rushing in. When the carbon tube failed to hold them apart, those titanium hemispheres would have slammed together on the mix of water, carbon fibre and people inside.

 

[Ziggurat]

Wouldn't just be the water that was rushing in. When the carbon tube failed to hold them apart, those titanium hemispheres would have slammed together on the mix of water, carbon fibre and people inside.

The domes are going to be pushed towards each other, bud depending on how fast the water rushes in between them, not necessarily for long enough that they impact. And in fact, from the photos of the wreckage, there seemed to be a pretty long section of material (maybe the flooring? don't know) relatively intact protruding from the rear dome. That suggests to be that the front dome can't have travelled very far towards the back dome, or that long section would have been squished lengthwise, and it wasn't.

 

[ponderingturtle]

A whole pressure compartment made of carbon fiber was his Big Idea, it was his Innovation and he became fixated on it to the point where he would not hear anything against it.

Carbon fiber is much lighter than steel, yes? Since OceanGate didn't have its own ships but had to rent them for expeditions, a submersible of the same size made of steel or titanium might have narrowed the options perhaps. Like maybe only a handful of ships in the world were really build to handle launching and retrieving something like that (and they're all taken), whereas practically any ship can handle something like the Titan?

That wasn't it, see with a steel or titanium pressure vessel it would likely have needed fancy floaties to give it positive buoyancy when it dropped its weights. But the lightness of carbon fiber made this unnecessary. The special foams that are used on a the real deep diving subs are very expensive and a major part of the cost.

 

[Spektator]

This is so close to being interesting.