Tourist submarine exploring Titanic wreckage disappears in Atlantic Ocean

[plym49.2]

If the porthole was the failure point then the pressure wave would have been a EXlosion not implosion?
I are not real smart and working in vacuums is about the max of my processing power

Edit: The obvious size difference of the Limiting factors viewports, they are 15" in diameter at the outside but taper to 3"? while being 7" thick.
Obviously completely different depth rating...

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Still an implosion. Huge outside pressure coming inside.

 

[PAE]

Presumed human remains recovered from within Titan wreckage, US Coast Guard says

Pieces of mangled craft brought ashore in Newfoundland, Canada, after five killed on voyage to Titanic wreck

www.theguardian.com

 

[ProjectTwin]

No. Not at 5500 psi external pressure. There is no "blow the end bells off" in this scenario. As soon as the CF stopped resisting, those bells either collided at high velocity, or just fell away. There is no force to blow anything outward. The interior of the hull was at a vacuum of 12000 inches of mercury.

Help me understand.

Inside this thing should’ve been one atmosphere- 14.7 psi or so.

Outside the hull the forces would obviously become greater the deeper they go.

We know they didn’t get to the bottom before it imploded, but we don’t know exactly how deep they went so we don’t know the exact pressure differential.

I assume you’re saying the 12000inHg you’re talking about is what was experienced at the moment of implosion. A vacuum created due to pressure differential.

Because it wasn’t under vacuum until it was.

 

[plym49.2]

Help me understand.

Inside this thing should’ve been one atmosphere- 14.7 psi or so.

Outside the hull the forces would obviously become greater the deeper they go.

We know they didn’t get to the bottom before it imploded, but we don’t know exactly how deep they went so we don’t know the exact pressure differential.

I assume you’re saying the 12000inHg you’re talking about is what was experienced at the moment of implosion. A vacuum created due to pressure differential.

Because it wasn’t under vacuum until it was.

'Vacuum' is relative to the overall pressure differential. Thousands of psi against 14.7 is close enough to zero. :) So to the outside ocean at the point, that vessel was essentially at 0 psi, or a vacuum, even though they were at 14.7.

I believe I heard that they went radio silent and made boom-boom noise at 3500 feet. So not the full 12000 psi - which makes this all the worse as they were not even close.

 

[sdmuleman]

I am still wondering what provisions they had for controlling tilt and trim.

Probably just used static stability for pitch/roll - set it up where CG is below CB and it should stay more or less upright. Trim (i.e. attaining neutral buoyancy) would be more interesting. In large submarines it's done using trim tanks, but more difficult to do at deep depth. Likely used progressively releasable fixed ballast - i.e. can drop ballast by x lb increments until you get roughly neutral and then use thrusters for altitude control.

No. Not at 5500 psi external pressure. There is no "blow the end bells off" in this scenario. As soon as the CF stopped resisting, those bells either collided at high velocity, or just fell away. There is no force to blow anything outward. The interior of the hull was at a vacuum of 12000 inches of mercury.

Neither is entirely accurate. Depends a lot of the specifics of how the collapse happens. The bells aren't going to just fall away. The implosion would be a very dynamic event with very high forces. If the cylinder collapses around the axis you could very well wind up with a jet along the axis blowing ends off.

 

[plym49.2]

Probably just used static stability for pitch/roll - set it up where CG is below CB and it should stay more or less upright. Trim (i.e. attaining neutral buoyancy) would be more interesting. In large submarines it's done using trim tanks, but more difficult to do at deep depth. Likely used progressively releasable fixed ballast - i.e. can drop ballast by x lb increments until you get roughly neutral and then use thrusters for altitude control.



Neither is entirely accurate. Depends a lot of the specifics of how the collapse happens. The bells aren't going to just fall away. The implosion would be a very dynamic event with very high forces. If the cylinder collapses around the axis you could very well wind up with a jet along the axis blowing ends off.

And if too many passengers - err, 'crew' - slide forward to gawk out the port, or huddle to the rear 'cuz someone up front is taking a smelly shit, well, not likely recoverable.

 

[WLDWUN]

Neither is entirely accurate. Depends a lot of the specifics of how the collapse happens. The bells aren't going to just fall away. The implosion would be a very dynamic event with very high forces. If the cylinder collapses around the axis you could very well wind up with a jet along the axis blowing ends off.

very much this is what I would expect

 

[ProjectTwin]

'Vacuum' is relative to the overall pressure differential. Thousands of psi against 14.7 is close enough to zero. :) So to the outside ocean at the point, that vessel was essentially at 0 psi, or a vacuum, even though they were at 14.7.

I believe I heard that they went radio silent and made boom-boom noise at 3500 feet. So not the full 12000 psi - which makes this all the worse as they were not even close.

That’s what I figured you were getting at. As the pressure differential increased that 14.7psi was effectively a vacuum at depth, but relative to the people inside, it wasn’t a vacuum.

 

[gt1guy]

I believe I heard that they went radio silent and made boom-boom noise at 3500 feet. So not the full 12000 psi - which makes this all the worse as they were not even close.

Exactly. They were never going to make it. That sub was completely compromised and fucked before it ever left the surface.

It also tells me that the folks who took the last trip were this >< close to the same outcome. A few more minutes on bottom might have been all it took.

So the thing let go at 1557psi and they were headed to 5340psi.

 

[plym49.2]

Exactly. They were never going to make it. That sub was completely compromised and fucked before it ever left the surface.

It also tells me that the folks who took the last trip were this >< close to the same outcome. A few more minutes on bottom might have been all it took.

So the thing let go at 1557psi and they were headed to 5340psi.

Safety factor .3-ish?

 

[PAE]

I learned this crap back 50 or so years ago when I was certified for open water diving but was mistaken on a few figures.

One atmosphere (101.325 kPa or 14.7 psi) is also the pressure caused by the weight of a column of freshwater of approximately 10.3 m (33.8 ft).

 

[WLDWUN]

Exactly. They were never going to make it. That sub was completely compromised and fucked before it ever left the surface.

It also tells me that the folks who took the last trip were this >< close to the same outcome. A few more minutes on bottom might have been all it took.

So the thing let go at 1557psi and they were headed to 5340psi.

this is what I do not understand.
the lost comms 1:45 after they started decent, they should have been almost 90% of the way there.
I find it hard to believe it collapsed at 3500 feet.

• it surely would have collapsed on the last dive to a pressure almost 4 times that depth.
• the debris field would be larger having to fall almost 2 kilometers in currents.
• why would it have taken 1:45 to only go 3500 feet?

12pm GMT/8am ET: The submersible starts what should be a two-hour descent to the Titanic wreck, nearly 4,000 metres down, according to the US Coast Guard.

1.45pm GMT/9.45am ET: Communications between the submersible and the surface vessel are lost 1 hour and 45 minutes after starting its descent.

 

[sdmuleman]

And if too many passengers - err, 'crew' - slide forward to gawk out the port, or huddle to the rear 'cuz someone up front is taking a smelly shit, well, not likely recoverable.

Certainly not unrecoverable. Likely would cause noticeable change in pitch, but doubt it would more than 10* or so. Total vehicle weight is something like 5500 lb, so people are not a terribly huge fraction of the mass, and not much room for them to go far anyway.

I learned this crap back 50 or so years ago when I was certified for open water diving but was mistaken on a few figures.

One atmosphere (101.325 kPa or 14.7 psi) is also the pressure caused by the weight of a column of freshwater of approximately 10.3 m (33.8 ft).

Easy rule is divide depth in ft by 2 to get PSI. Overstates pressure by a fair bit, but good enough for ballpark math.

this is what I do not understand.
the lost comms 1:45 after they started decent, they should have been almost 90% of the way there.
I find it hard to believe it collapsed at 3500 feet.

• it surely would have collapsed on the last dive to a pressure almost 4 times that depth.
• the debris field would be larger having to fall almost 2 kilometers in currents.
• why would it have taken 1:45 to only go 3500 feet?

12pm GMT/8am ET: The submersible starts what should be a two-hour descent to the Titanic wreck, nearly 4,000 metres down, according to the US Coast Guard.

1.45pm GMT/9.45am ET: Communications between the submersible and the surface vessel are lost 1 hour and 45 minutes after starting its descent.

3500 ft has to be an error. I'm betting it's actually 3500 meters.

 

[CrustyJeep]

I believe I heard that they went radio silent and made boom-boom noise at 3500 feet. So not the full 12000 psi - which makes this all the worse as they were not even close.

Huh? They were an hour and forty five minutes into a two hour decent, weren't they? That's what I remember hearing.

 

[CrustyJeep]

That’s what I figured you were getting at. As the pressure differential increased that 14.7psi was effectively a vacuum at depth, but relative to the people inside, it wasn’t a vacuum.

Right. I put it that way partly for effect (12000 inches of mercury ), and partly to bring a different perspective into the discussion. Anyway, there's no such thing as a vacuum, just like there's no such thing as dark, they both describe an absence of something. It's the delta between something and a lack of it that's important.

 

[gt1guy]

Safety factor .3-ish?

What safety factor? The pressure at 12,000FSW is 5340psi. The pressure at 3500FSW is 1557.5psi.

Depth in feet of saltwater times .445 gives you the pressure in psi.

I learned this crap back 50 or so years ago when I was certified for open water diving but was mistaken on a few figures.

One atmosphere (101.325 kPa or 14.7 psi) is also the pressure caused by the weight of a column of freshwater of approximately 10.3 m (33.8 ft).

Fresh water you would multiply by .443 to get the psi at a given depth.

this is what I do not understand.
the lost comms 1:45 after they started decent, they should have been almost 90% of the way there.
I find it hard to believe it collapsed at 3500 feet.

• it surely would have collapsed on the last dive to a pressure almost 4 times that depth.
• the debris field would be larger having to fall almost 2 kilometers in currents.
• why would it have taken 1:45 to only go 3500 feet?

12pm GMT/8am ET: The submersible starts what should be a two-hour descent to the Titanic wreck, nearly 4,000 metres down, according to the US Coast Guard.

1.45pm GMT/9.45am ET: Communications between the submersible and the surface vessel are lost 1 hour and 45 minutes after starting its descent.

We may never learn how it actually played out.

• it surely would have collapsed on the last dive to a pressure almost 4 times that depth.

Not necessarily. Going to bottom and back up is not static, it's a very dynamic operation. It's compressing and relaxing.......breathing if you will. Each time they went down and back, the CF hull was degraded a bit, compounding the problem.
So whatever depth it did fail at, that was the point where the compromised hull couldn't hold back the outside pressure any longer.

• the debris field would be larger having to fall almost 2 kilometers in currents.

Good point and it very well could have been deeper when they all got really small. Would be nice to know what the currents were at the time.

• why would it have taken 1:45 to only go 3500 feet?

Loud cracking noises maybe?


They should have had some kind of data logger on the sub. But cutting corners seems to be all they were good at.

 

[Tech Tim]

This guy gets it...

 

[ProjectTwin]

Safety factor .3-ish?

I wear this shit, but it’s a joke. Sure as fuck wouldn’t apply to building a sub.

 

[ProjectTwin]

What safety factor? The pressure at 12,000FSW is 5340psi. The pressure at 3500FSW is 1557.5psi.

Depth in feet of saltwater times .445 gives you the pressure in psi.






Fresh water you would multiply by .443 to get the psi at a given depth.






We may never learn how it actually played out.


Not necessarily. Going to bottom and back up is not static, it's a very dynamic operation. It's compressing and relaxing.......breathing if you will. Each time they went down and back, the CF hull was degraded a bit, compounding the problem.
So whatever depth it did fail at, that was the point where the compromised hull couldn't hold back the outside pressure any longer.




Good point and it very well could have been deeper when they all got really small. Would be nice to know what the currents were at the time.




Loud cracking noises maybe?


They should have had some kind of data logger on the sub. But cutting corners seems to be all they were good at.

They had a hull monitoring system that I read about, but with a CF hull it’s useless.

I have no idea how they thought carbon fiber under repeated stresses like they were subjecting it to, would hold up forever.

I had a buddy that designed and produced RC parts. He wanted to make some parts out of Ti even after we discussed how Ti was a bad material for the application (CV shafts).

He produced them anyway. Sent out a lot of replacements as a result.

I was like…”Hey…remember when we talked about Ti being the wrong material for that application?”

 

[arse_sidewards]

I can't help but wonder if it would have been cheaper to build the tube out of steel but they didn't because they hired a bunch of textbook engineers who like to build shit using "cool modern techniques" like CF, aluminum extrusions and all the other garbage that's all the rage among the engineering circle jerk crowd who would rather showboat than build boring but practical shit.

I have no idea how they thought carbon fiber under repeated stresses like they were subjecting it to, would hold up forever.

CF pressure vessels take it just fine.

Obviously not stress in the same directions but still cyclical loading.

 

[Firstram]

I can't help but wonder if it would have been cheaper to build the tube out of steel but they didn't because they hired a bunch of textbook engineers who like to build shit using "cool modern techniques" like CF, aluminum extrusions and all the other garbage that's all the rage among the engineering circle jerk crowd who would rather showboat than build boring but practical shit.



CF pressure vessels take it just fine.

Obviously not stress in the same directions but still cyclical loading.

From what I've read recently, a steel vessel built to withstand those pressures is not buoyant! Sophisticated floatation is required. The CF hull weighed less and floated, until it didn't!

 

[redneckengineered]

They had a hull monitoring system that I read about, but with a CF hull it’s useless.

"Real time hull monitoring system." Think about that in context with a submarine and try not to laugh. Also I heard that clown Stockton talk about how the porthole would crack under pressure before full failure giving them ample warning to get to the surface. Again, this is a submarine we're talking about. Pretty sure anything that alerts you to catastrophic failure in "real time" is not a good safety measure.

 

[redneckengineered]

I hope he got a little Windows popup that said "hull crush warning"

 

[plym49.2]

CF pressure vessels take it just fine.

Obviously not stress in the same directions but still cyclical loading.

CF is stronger in tension. Sub was in compression.

 

[Welby]

I hope he got a little Windows popup that said "hull crush warning"

 

[Arps]

 

[Void_of_Light]

I hope he got a little Windows popup that said "hull crush warning"

I bet he did, .2 milliseconds before the pressure got to him.

 

[redneckengineered]

I bet he did, .2 milliseconds before the pressure got to him.

Can't claim it wasn't in real time.

 

[arse_sidewards]

CF is stronger in tension. Sub was in compression.

Right, but flex is flex. Materials don't care if you're doing it the easy way or the hard way, they just care how much they're deforming.

 

[arse_sidewards]

From what I've read recently, a steel vessel built to withstand those pressures is not buoyant! Sophisticated floatation is required. The CF hull weighed less and floated, until it didn't!

That makes sense.