Titanic Sight Seeing Sub...

[Citysnaps]

OT, but,


The nothingburger is the Hunter Biden is a source of corruption issues for dad. No one disputes that Hunter himself has problems, but none of those problems reflect on dad's fitness for office.

Reminds me of when Jimmy Carter was President, with his brother Billy doing some sketchy stuff in Libya. And the R's tried to morph that into influence pedaling the President, holding Senate hearings. In the end, a nothingbuger for Jimmy.

 

[Herdfan]

Sure, they heard a noise that sounded like an implosion at the right time. But there was also rumors of people hearing knocking sounds. I happen to think the decision to look for more evidence was the humane thing to do. If my loved one were missing, it would gut me if they called off the search early just because someone heard something that could have been the sub imploding. Now the families know for sure. As rough as it is, I'd rather have evidence of what happened then guesses based on a sound heard by the Navy.

I agree. But the media kept this going. I hope the families were given all the information available, both good and bad.

 

[MEJHarrison]

But the media kept this going.

To some degree, I'm sure that's true. But I don't see it that way. I think the majority of the "blame" lies with the viewers. People were super interested in this story, so the news fed them that. If they didn't, they would have left and gone elsewhere. If you're a business, you meet your customer's demands, you don't send them to the competition. Giving people news they're uninterested in doesn't sell papers.

I also don't think there's any blame here to toss around. Stories like this draw attention. What's the harm in them reporting on it? Granted, I don't keep the news on 24 hours a day like some people I know. If I did, I'm sure I would have grown tired of the coverage. But I don't do that. I control my own intake, not the media. When I've had enough, I walk away. So the media "keeping it going" wasn't something that bothered me in the slightest. Just as the latest hot song might be getting played WAY too much on the radio, but since I don't listen to the radio or know what the hot songs are these days, I honestly don't care one way or the other.

My long winded point is, I think the viewers are at least as much to blame for "keeping it going" as the media. I personally think they're a lot more responsible for keeping it going to be honest.

 

[Huntn]

OT, but,


The nothingburger is the Hunter Biden is a source of corruption issues for dad. No one disputes that Hunter himself has problems, but none of those problems reflect on dad's fitness for office.

Throw it against the minions and see if it sticks…

 

[theorist9]

I keep seeing a figure that the hull would have collapsed in 1 ms (a good thing for those unfortunate souls inside, since that's longer than it takes the human brain to register pain). But no one has shown the source of that figure. The radius of the Titan's carbon fiber tube was 71 cm, and for it to collapse in 1 ms would require a rate of acceleration of the carbon fiber shell towards the Titan's centerline of 2 * 71 cm/(1 ms)^2 = 1,420,000 m/s^2 = 145,000 g. Anyone know it was derived?

 

[mollyc]

OceanGate tried to scrub the internet clean of traces that it ever existed, taking down its Facebook, Instagram, Twitter, and LinkedIn pages

OceanGate, the deep-sea exploration company that created the Titan submersible, has removed its Facebook, Instagram, Twitter, and LinkedIn accounts.

www.insider.com

 

[Nycturne]

I keep seeing a figure that the hull would have collapsed in 1 ms (a good thing for those unfortunate souls inside, since that's longer than it takes the human brain to register pain). But no one has shown the source of that figure. The radius of the Titan's carbon fiber tube was 71 cm, and for it to collapse in 1 ms would require a rate of acceleration of the carbon fiber shell towards the Titan's centerline of 2 * 71 cm/(1 ms)^2 = 1,420,000 m/s^2 = 145,000 g. Anyone know it was derived?

They were quoting someone who was rattling something off. It wasn’t derived. I’ve seen quotes as high at 30-40ms. At 30ms, my napkin says it would be a “mere” 80g of acceleration needed using your mathematical approach.

That said, your math seems a little bit off? You take the whole diameter of the pressure vessel when the shell traveling the radius would “complete” the implosion as the opposite sides of what was the shell meet. Since the pressure can be assumed to be equal on all sides for something like this, I don’t think you’d need to double the radius.

Someone did try to math out some of the numbers, assuming the Titan failed about halfway down, and got accelerations in excess of 3800g, and an implosion time of around 7ms. This is all rough numbers, and models the Titan as a perfect cylinder.

The Insane Numbers of a "Catastrophic Implosion"

Okay, strap in everyone, it’s time for math and physics. All of the coverage of the recent accident of the Titan submarine when it was attempting to go down to the wreck of the Titanic refer to the accident as a “catastrophic implosion”, but I have yet to see any of the coverage thoroughly describe

www.linkedin.com

 

[theorist9]

That said, your math seems a little bit off? You take the whole diameter of the pressure vessel when the shell traveling the radius would “complete” the implosion as the opposite sides of what was the shell meet. Since the pressure can be assumed to be equal on all sides for something like this, I don’t think you’d need to double the radius.

I didn't double the radius. The "2" comes from the formula .

For constant acceleration ("s" is distance, which in this case is "r" [the radius]):
s = 1/2 a t^2
=> a = 2 s/t^2
=> a = 2 r/t^2

I skimmed throught the article you linked, and his approach doesn't make physical sense to me. He's using the mass of the Titan and the force from the water to determine the acceleration, but what's being accelerated inward isn't just the Titan's shell--it's the water as well.

This seems to be a very complex problem. I'll do some more looking to see if I can find anything. If someone has come up with a back-of-the envelope approach for it, I suspect it would need to be quite clever, like G.I. Taylor's famous dimensional analysis that estimated the (then-classified) yield of Trinity test from photos published in Life magaine.

 

[Nycturne]

I didn't double the radius. The "2" comes from the formula .

For constant acceleration ("s" is distance, which in this case is "r" [the radius]):
s = 1/2 a t^2
=> a = 2 s/t^2
=> a = 2 r/t^2

I skimmed throught the article you linked, and his approach doesn't make physical sense to me. He's using the mass of the Titan and the force from the water to determine the acceleration, but what's being accelerated inward isn't just the Titan's shell--it's the water as well.

This seems to be a very complex problem. I'll do some more looking to see if I can find anything. If someone has come up with a back-of-the envelope approach for it, I suspect it would need to be quite clever, like G.I. Taylor's famous dimensional analysis that estimated the (then-classified) yield of Trinity test from photos published in Life magaine.

Fair, my physics is about as rusty as it can get.

The implosion time of 1 millisecond does seem rather fast, but it doesn’t necessarily need to be that much slower to bring things into the realm of ”merely bonkers”, and it can be quite a bit longer and still be in the realm of being perceived as instantaneous by the poor saps aboard the craft.

 

[Yoused]

Fair, my physics is about as rusty as it can get.

The implosion time of 1 millisecond does seem rather fast, but it doesn’t necessarily need to be that much slower to bring things into the realm of ”merely bonkers”, and it can be quite a bit longer and still be in the realm of being perceived as instantaneous by the poor saps aboard the craft.

A single frame of digital video (30fps, IIRC) has a latency of about 33ms. An incandescent light bulb flickers at about twice that rate, and sometimes that flicker can be perceived. Thus, 17ms is right around the limit of momentary perception. If the collapse took even 20ms, it would have seemed instantaneous to the tourists.

Yet, it is quite likely that the vessel did advise the people in it that it was preparing to fail. They probably heard ominous creaking and groaning before the end, but just kept drinking their coffee. Luckily, there is no black box, that we know of.

 

[Nycturne]

A single frame of digital video (30fps, IIRC) has a latency of about 33ms. An incandescent light bulb flickers at about twice that rate, and sometimes that flicker can be perceived. Thus, 17ms is right around the limit of momentary perception. If the collapse took even 20ms, it would have seemed instantaneous to the tourists.

That's kinda what I'm getting at. Getting into that range brings down the accelerations required to traverse the radius of the cylinder. Let's just use the simpler formula from theorist9:

1ms - 145,000 g
10ms - 1500 g
20ms - 360 g

A couple orders of magnitude shaved off because of the squared term. So really, it seems to me that you can still be in the range of "instantaneous" and not requiring over 100 thousand gravities of acceleration to accomplish it. At which point I kinda just accept it's absurdly fast.

Yet, it is quite likely that the vessel did advise the people in it that it was preparing to fail. They probably heard ominous creaking and groaning before the end, but just kept drinking their coffee. Luckily, there is no black box, that we know of.

Probably won't know. As I've mentioned before, carbon fiber tends to just give up the ghost when it does. I wouldn't be surprised if there wasn't much warning. Maybe something akin to "Mind that bus. What bus? Splat."

I skimmed throught the article you linked, and his approach doesn't make physical sense to me. He's using the mass of the Titan and the force from the water to determine the acceleration, but what's being accelerated inward isn't just the Titan's shell--it's the water as well.

Does the mass of the water make an appreciable difference in the end result, I wonder? It seems like the effects would get drowned out at these depths. Much like the effect of the sub itself is drowned out and ignored in the calculation.

 

[rdrr]

That's kinda what I'm getting at. Getting into that range brings down the accelerations required to traverse the radius of the cylinder. Let's just use the simpler formula from theorist9:

1ms - 145,000 g
10ms - 1500 g
20ms - 360 g

A couple orders of magnitude shaved off because of the squared term. So really, it seems to me that you can still be in the range of "instantaneous" and not requiring over 100 thousand gravities of acceleration to accomplish it. At which point I kinda just accept it's absurdly fast.



Probably won't know. As I've mentioned before, carbon fiber tends to just give up the ghost when it does. I wouldn't be surprised if there wasn't much warning. Maybe something akin to "Mind that bus. What bus? Splat."



Does the mass of the water make an appreciable difference in the end result, I wonder? It seems like the effects would get drowned out at these depths. Much like the effect of the sub itself is drowned out and ignored in the calculation.

So instead of using all this math, (I should have stayed awake in those advanced math classes), I'll just refer to my own experience. Although I clearly didn't die, I was knocked on the side of my head by a temporarily nailed truss on a barn when it came swinging down. In one movement I was standing there watching my dad shake the frame , 30 minutes later I woke up in the hospital dazed with severe neck and head pain. The in between timeframe, is a complete blank.

 

[Yoused]

The in between timeframe, is a complete blank

I hit a car on my bicycle. I was going pretty fast and did not have time to stop. I remember jumping up and down in the street, cussing a blue streak, but the time between about 30 feet before impact to getting to my feet, which must have been at least two seconds, in not retrievable to my memory, because our brains tend to erase the specifics of trauma (I contend that Dianetics is nonsense).

On the other hand, actual dying is not well understood. The collapse was instantaneous, but we really have no idea about the nature of mental function and perception in the final moments.

 

[theorist9]

Does the mass of the water make an appreciable difference in the end result, I wonder? It seems like the effects would get drowned out at these depths. Much like the effect of the sub itself is drowned out and ignored in the calculation.

I suspect that neither the mass of the water nor the mass of the Titan's shell contribute significantly to the rate of collapse (see discussion below row of asterisks). But my issue with the LinkedIn article is that, according to the physical picture he presents, the mass of the water would need to be included, since he's determing the acceleration from the force exerted by the water, and the mass of what is pushed inward. Thus, regardless of whether his physical picture is correct or not (I don't think it is), it has a problem right from the start, which is that it's not self-consistent. [Plus he calculated p = 58 atm at 1900 m, when it's actually 188 atm.]

*************
According to this 2013 review article LeBlanc, J., Ambrico, J., Turner, S. (2014). Underwater Implosion Mechanics: Experimental and Computational Overview. In: Shukla, A., Rajapakse, Y., Hynes, M. (eds) Blast Mitigation. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-7267-4_6.

"The physics of an implosion event is shown to be similar to the collapse of cavitation and underwater explosion bubbles."

This is not my field, but models for bubble radius vs. time are typically based on the external pressure and other intensive (i.e., instrinsic) properties (those that don't depend on the amount of the substance). Some models use the density, kinematic viscosity, and surface tension of water; others use the density and speed of sound for both the water and the interior gas (which, for a cavitation bubble, would also be water). Extending that to the collapse of the Titan, I don't think the mass of either the shell or the water would be important determining factors for the rate of collapse (the mass of the water would matter only through its density).

Here's a sample equation from Geers, Thomas L., and Kendall S. Hunter. "An integrated wave-effects model for an underwater explosion bubble." The Journal of the Acoustical Society of America 111.4 (2002): 1584-1601 , as summarized in the above review article:

"Geers and Hunter (2002) have expanded upon previous work through the inclusion of wave effects in both the surrounding fluid as well as the internal bubble gasses through the use of doubly asymptotic approximations (DAA). The inclusion of these wave effects allows for bubble wall velocities in excess of the fluid sound speed by accounting for localized compressibility of the surrounding fluid. For the case of incompressible flow (no localized wave effects), the equation of motion for the bubble surface can be described using the Rayleigh–Plesset equation. The corresponding equation of motion with the inclusion of external fluid and internal gas compressibility through the DAA method is presented as:

""

[For those not familiar with the above notation: This is a second-order differential equation. The R's topped by one and two dots are the first and second derivatives, respectively, of the bubble radius with respect to time.]

For a simpler, approach, there's the standard Rayleigh–Plesset equation (https://en.wikipedia.org/wiki/Rayleigh–Plesset_equation#cite_note-Kudryashov2015-8). Alas, I tried solving it, and was unable to.

Or we could go even simpler, and use the Rayleigh equation, which ignores the surface tension and viscosity included in Rayleigh-Plesset. According to Kudryashov, Nikolay A., and Dmitry I. Sinelshchikov. "Analytical solutions of the Rayleigh equation for empty and gas-filled bubble." Journal of Physics A: Mathematical and Theoretical 47.40 (2014): 405202 , if we ignore the pressure from the interior gas (which would be insignificant relative to the outside pressure), the collapse time, Tc, for a spherical bubble containing no gas can be obtained from:
Tc = 𝛏 R * sqrt (𝛒/p)
where:
𝛏 = 0.914681
R= bubble diameter
𝛒 = density of water
p = water pressure
Thus, for a spherical bubble whose radius equals that of the Titan's carbon fiber cylinder, and ignoring the Titan's shell, and the viscosity and surface tension of the water (and other things), we have, as a first approximation (I plugged the numbers into Mathematica and let it do the unit conversions), collapse times of 4 ms and 6 ms, respectively, at the Titanic's depth and at half the Titanic's depth:

Note: Here I use the external diameter/2 rather than the internal diameter/2 I used in my first post.

Would any fluid dynamics experts like to chime in?

 

[Roller]

We’ll never know if the implosion happened too quickly to register on the occupants’ consciousness. But surely they were aware they were doomed, whether by a sudden, catastrophic failure or gradual suffocation. I can’t imagine the mental anguish that realization would have caused, especially for the father and son.