Titanic tourist sub missing

[SpuriusMaximus]

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.

I'm pretty sure that expanding in the direction of the axis of the sub would be a tremendous kick in that direction, even if it's just for 1mm, if it's tensioned by literally thousands of tons of force. A thousand tons times 1mm is the same as a ton times 1m.

 

[smartcooky]

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.

Yeah, syntactic foam. It ain't cheap, and you need a lot of it to give a heavy bathyscaphe buoyancy.

 

[SpuriusMaximus]

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.

At that exact dimension? Sure. But it's very much possible to have positive buoyancy with a titanium or even steel hull, if you make it big enough. It's just a simple matter of the square-cube law.

 

[ponderingturtle]

At that exact dimension? Sure. But it's very much possible to have positive buoyancy with a titanium or even steel hull, if you make it big enough. It's just a simple matter of the square-cube law.

Pressure vessels do not follow the square cube law Bigger vessels need proportionately thicker walls as they are flatter and worse and transferring the load around the object.

As a surface vessel no problem but when you load it all to a few hundred thousand PSI you have issues.

 

[Ziggurat]

I'm pretty sure that expanding in the direction of the axis of the sub would be a tremendous kick in that direction

When the carbon fiber hull collapses, we can expect the titanium dome to expand in the direction towards the center of the ship, since it's not being pushed back on from that direction anymore. But it's still being pushed on just as hard by the water from the front. And that water is going to still be pushing the window just as much, so it's still going to keep the window in place as long as there's a pressure differential between the outside front and the inside front. The expansion of the titanium dome towards the center won't make any difference to the window, because any acceleration towards the center is going to be caused by the water on the outside, and that's going to accelerate the window just as much as the titanium. And because the speed of sound in titanium is so much higher than the speed of sound in water, the expansion of the titanium is going to finish while the inside pressure is still low, and the window is still being pushed into the dome by the outside water pressure.

The window is only going to pop out when you have overpressure from the inside. And the expansion of the titanium dome isn't going to cause that overpressure.

 

[Gord_in_Toronto]

This is so close to being interesting.

It might be if we had some actual data. What we are seeing is here a considerable amount of hand waving. The actual investigation is much more likely to have the resources to draw a definite conclusion.

But don't let us stop you.

 

[SpuriusMaximus]

When the carbon fiber hull collapses, we can expect the titanium dome to expand in the direction towards the center of the ship, since it's not being pushed back on from that direction anymore.

Pretty sure the bounce part would be around the centre of mass or there abouts. Whatever other direction it's pushed towards, is on top of that. Unless the acceleration is enough to get into the GR domain, I guess, we still have a different acceleration between the two ends there. And a rebound that would pull it back from the "weight" at the end. Quite violently.

 

[whoanellie]

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.

There was testimony this morning that the motivation for the use of carbon fiber was, in fact, to eliminate the need for a highly specialized mother ship dedicated to the submersible. The submersible could be shipped around the world and used on a variety of available mother ships. The cost of a dedicated mothership would far outweigh the cost of specialized foam.

 

[jeremyp]

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.

Nobody is suggesting that is the case. The video tells us that whilst a lot of the carbon fibre was shoved into the rear dome, not all of it was. Some was scattered around the seabed.

So I don't see why a rogue piece couldn't have hit the window from the inside and then fallen out.

I'm not claiming that this is what happened, only that your reason for ruling it out seems tenuous at best.

When the hull collapses, the pressure doesn't just equalize, it overshoots before equalizing.

Yes I know that and not just because you have posted it before. The Slow Mo Guys have a video on YouTube in which they fired a gun under water and you can clearly see a cloud of gas expand from the muzzle, collapse in on itself and then expand again from the "rebound".

The question is where the collapse originated.

I don't think there is a question at all. I think the video clearly shows that the interface between the carbon fibre and the front ring failed. It was predicted by several people including on this thread. At this point, I don't think anybody is arguing against it.

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

I thought you were arguing about what caused the window to pop out after the hull collapse. I don't know, and I don't think it's that important.

 

[Ziggurat]

Nobody is suggesting that is the case. The video tells us that whilst a lot of the carbon fibre was shoved into the rear dome, not all of it was. Some was scattered around the seabed.

So I don't see why a rogue piece couldn't have hit the window from the inside and then fallen out.

Under what conditions could it have hit the window hard enough to knock it out?

Not during the initial collapse. The failure started at the joint between the front titanium ring and the carbon fiber hull. That failure would have pushed the carbon fiber in and then back towards the rear dome. None of it is going to start out shooting towards the window. Some of it might shoot towards the window during the rebound, but that's also when you're going to get overpressure on the inner side from the collapse, and that pressure wave is going to travel faster than the carbon fiber, and it's going to blow the window out before any of the rebounding carbon fiber pieces are going to hit it.

I thought you were arguing about what caused the window to pop out after the hull collapse. I don't know, and I don't think it's that important.

It might not be that important, but I think it's interesting.

 

[jeremyp]

Under what conditions could it have hit the window hard enough to knock it out?

Have you got any idea what energy is involved in such an implosion?

Not during the initial collapse. The failure started at the joint between the front titanium ring and the carbon fiber hull. That failure would have pushed the carbon fiber in and then back towards the rear dome.

Exclusively?

None of it is going to start out shooting towards the window.

you've done simulations to prove this, have you? Can we see the results?

Some of it might shoot towards the window during the rebound, but that's also when you're going to get overpressure on the inner side from the collapse, and that pressure wave is going to travel faster than the carbon fiber, and it's going to blow the window out before any of the rebounding carbon fiber pieces are going to hit it.

In my opinion the pressure wave is the more likely scenario, but this is just my opinion and, unless you have some sort of evidence, it's just yours too.

It might not be that important, but I think it's interesting.

Fair point.

 

[Ziggurat]

Have you got any idea what energy is involved in such an implosion?

Let's do the math right now to get a ballpark figure. It's actually quite easy.

The pressure at that depth is about 40 MPa, or 4x10⁷ N/m², or to change to units which will be more convenient, 4x10⁷ J/m³ (recall that 1 Nm = 1 J). The volume of the Titan sub pressure vessel was around 4.2 meters long and around 1.7 meter diameter. Assuming a cylindrical volume (a bit of an overestimate), that's about 9.5 m³, let's round up to 10 m³. The potential energy of holding back 40 MPa of pressure from a 10 m³ volume is simply the product of the two (I can do a mathematical proof if you like, or you can trust dimensional analysis), or about 4x10⁸ Joules.

The explosive energy of one metric ton of TNT is about 4 gigajoules of energy, or 4x10⁹ J. We're working with about a tenth of that, so around 100 kg equivalent TNT. This is a bit of an overestimate, but no by all that much.

So yes, I have a pretty good idea of the energy involved, and yes it is a lot.

Exclusively?

Pretty much.

you've done simulations to prove this, have you? Can we see the results?

I can understand which direction forces are being applied, and which direction things will move in. Without evidence I could only guess where the failure started, but we have evidence of that, so I'm not really guessing.

I wouldn't stake my life on my prediction, but I'd make an avatar bet any day of the week.

 

[jeremyp]

Pretty much.

Not exclusively then. Also denied by the fact that the video shows some carbon fibre not in the rear dome but strewn on the seabed.

I wouldn't stake my life on my prediction, but I'd make an avatar bet any day of the week.

I won't be taking you up on that bet because I agree that the most likely scenario is the pressure wave forcing it out. I was just challenging your apparent claim to absolute knowledge of the event.

 

[Ziggurat]

Also denied by the fact that the video shows some carbon fibre not in the rear dome but strewn on the seabed.

That conclusion doesn't follow. If all the carbon fiber got shoved into the aft dome during the implosion, that doesn't mean it will all stay there as the remains sink. It's going to be in pieces, and pieces can fall out subsequent to the implosion.

 

[smartcooky]

That conclusion doesn't follow. If all the carbon fiber got shoved into the aft dome during the implosion, that doesn't mean it will all stay there as the remains sink. It's going to be in pieces, and pieces can fall out subsequent to the implosion.

Indeed. There is this thing called a debris field, but Titan's was quite limited.

If Titan imploded at the depth the evidence suggests, then there was another 300-400 metres left before the wreckage reached the bottom, so plenty of time for bits of CF to fall away. But those bits still remained close, within a few feet of the wreckage of the hull and aft dome. This is not so for the forward titanium dome, which ended up a considerable distance away. Being as heavy as it was, it should have fallen straight down... I estimate from looking at the USCG video, it was over 25 feet away! That is a very long way for something that heavy to have simply "fallen off".

 

[Ziggurat]

That is a very long way for something that heavy to have simply "fallen off".

Maybe that's all that went wrong: the front fell off.

 

[smartcooky]

Maybe that's all that went wrong: the front fell off.

Haha, Fred Dagg!

Actually, that wasn't the link I was expecting. There was actually an occasion when the front door of Titan literally fell off onto the deck of the ship that was carrying it.

https://www.reddit.com/r/OceanGateTitan/comments/1flhntq/forward_dome_fell_off_during_recovery/

 

[Ziggurat]

Haha, Fred Dagg!

Actually, that wasn't the link I was expecting. There was actually an occasion when the front door of Titan literally fell off onto the deck of the ship that was carrying it.

https://www.reddit.com/r/OceanGateTitan/comments/1flhntq/forward_dome_fell_off_during_recovery/

Not a coincidence. I recently saw a YouTube video of someone talking about this whole mess, and he actually cut between a clip of that and a clip of Fred Dagg saying "The front fell off".

 

[Myriad]

Maybe that's all that went wrong: the front fell off.

Back when the sub was still "missing" I non-seriously suggested that James Cameron should fund the search and rescue operation in return for exclusive movie rights. At this point, if he wanted to film a movie of the tragic story of the Titan it would have to be a comedy.

"Only four bolts? Surely you can't be serious!"

Every removable part of every submersible hull I've ever seen has had the maximum possible number of bolts all around it, even when the operating pressure would only act to hold the part on tighter. Might there be some other reason for using so many bolts? Like, to prevent lateral shifting under pressure that could cause... pretty much exactly what happened to Titan?

 

[Skeptical Greg]

I must be really expensive to drill through titanium. They saved a lot of money with only four bolts.