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So, you turn diving down to the Titanic into a tourist business..what could go wrong?

bobl said:
My ride would have ended the moment I was told that I would be bolted in without any method of exit. Claustrophobia is a bitch.
Click to expand...

+1

I’m not claustrophobic, but being bolted in with no means of self escape on the surface is just dumb.
 
Climber said:
The issue doesn't seem to be the shape as much as the interface. Under those kinds of forces, the compression of different materials is going to be different and any difference is going to result in stresses where you really, really don't want them.
Click to expand...

I think the consensus is that the carbon tube fractured / delaminated.
 
Climber said:
The issue doesn't seem to be the shape as much as the interface. Under those kinds of forces, the compression of different materials is going to be different and any difference is going to result in stresses where you really, really don't want them.
Click to expand...

I think most experts are actually pointing towards the tube shape and the choice of using carbon fiber.

The vid addresses it a bit at 6min.

[YOUTUBE]6LcGrLnzYuU[/YOUTUBE]
 
Vid makes it clear. They willfully ignored safety standards and the fate of such happened.
 
Enchanter said:
I think most experts are actually pointing towards the tube shape and the choice of using carbon fiber.

The vid addresses it a bit at 6min.

[YOUTUBE]6LcGrLnzYuU[/YOUTUBE]
Click to expand...

^ I love that guys channel and boy oh boy does he have the bonifedes to comment on this disaster.
 
Great video. "not malice, stupidity."
 
Quahog said:
I beg to differ.

As far as I can tell, he was never licensed as any kind of engineer and never worked in the field, much less kept current in his field of study. He may have studied aeronautical engineering in college, but this disaster happened almost 40 years later. Basically, he could fly an airplane. I don't see how that background can have any bearing on designing and building a piece of equipment meant to withstand pressures at a depth that is over 5x what a modern military submarine is designed to endure.
Click to expand...

I mean, at the end of the day, I would say from a process/development perspective, it shouldn't really matter.

Anytime you are designing a new system of complexity of any type, particularly mechanical/physical systems, you should never rely on a single point of design as a potential failure. You need to get independent 3rd party review of critical systems.

It is essentially the principles of peer review applied in the design practice. To consider your design successful, you should be successfully overcoming challenges to your designs before finalizing production, regardless of how qualified you may be or if you are the global leader in your field.

This dude clearly wasn't interested in the reviews of others. How much do you want to bet he was a huge Nikloa Tesla fan?
 
Abacinator said:
I'm no engineer but I do know that EVERY OTHER submersible designed for extreme depths use spheres for the occupants. Do you think there's a reason for that?
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Most definitely, a sphere is structurally much stronger than a tube, that's a pretty basic understanding in engineering.

However, even carbon fiber built in a spherical manner would likely eventually fail due to the factors of cycles and interfaces with other materials. You can't use carbon fiber for the entire structure whereas you can use steel or titanium for the entire (mostly, aside from ports) structure.

If Rush had been diligent to the extent that is necesary for the kinds of forces the sub would be subjected to, he would have built a carbon fiber test vehicle, unmanned, and put it through many cycles with an xray inspectino after each cycle to see what the forces involved would do to the carbon fiber structure. He didn't and now he and others are dead as a result of his idiot approach.
 
Might be a dumb question, but...

I recall one of the interesting tidbits about the SR71 construction (also titanium) was that it was specifically engineered in a way that leaked fuel on the ground, necessitating refueling immediately after takeoff, because the speeds / pressures / temperatures at cruising conditions would swell the metal to fill the gaps.

In theory...couldn't you do something in the reverse for a submarine? Ie, engineer it in a way that as the pressure builds, it actually gets stronger / more secure?

I feel like the sphere obviously works, but in this day and age of AI assisted tools, we may see some crazy bulbous / tetrahedron / whatever designs start getting tested with that principle in mind.
 
NorCalAthlete said:
Might be a dumb question, but...

I recall one of the interesting tidbits about the SR71 construction (also titanium) was that it was specifically engineered in a way that leaked fuel on the ground, necessitating refueling immediately after takeoff, because the speeds / pressures / temperatures at cruising conditions would swell the metal to fill the gaps.

In theory...couldn't you do something in the reverse for a submarine? Ie, engineer it in a way that as the pressure builds, it actually gets stronger / more secure?

I feel like the sphere obviously works, but in this day and age of AI assisted tools, we may see some crazy bulbous / tetrahedron / whatever designs start getting tested with that principle in mind.
Click to expand...

I'm spitballing here so bear with me. I think the property you hinting at would be work hardening. I'm not sure that thermal contraction would help you much in trying to gain strength in a pressure vessel. Maybe the wall thickness of the sphere increases a tiny amount at depth due to the cold temps but my scientific wild ass guess would be that it is a negligible gain.

Work hardening is an interesting process. I suppose it can be helpful in the right circumstances. In my world its usually a PITA resulting from dull tools.

https://www.cnccookbook.com/work-hardening-strain-hardening-machinists-guide/
 
NorCalAthlete said:
Might be a dumb question, but...

I recall one of the interesting tidbits about the SR71 construction (also titanium) was that it was specifically engineered in a way that leaked fuel on the ground, necessitating refueling immediately after takeoff, because the speeds / pressures / temperatures at cruising conditions would swell the metal to fill the gaps.

In theory...couldn't you do something in the reverse for a submarine? Ie, engineer it in a way that as the pressure builds, it actually gets stronger / more secure?

I feel like the sphere obviously works, but in this day and age of AI assisted tools, we may see some crazy bulbous / tetrahedron / whatever designs start getting tested with that principle in mind.
Click to expand...

The second vid in ctwo's post claims that the carbon fiber compressed a half inch more than the titanium at operational depths. I have no idea it that is true.

And because I'm that guy:
The SR-71 did leak, and it did require refueling immediately after takeoff. The SR-71 did not takeoff fully fueled because it would not be able to successfully abort the takeoff if there was an emergency due to the added weight of the excess fuel.
 
tzrider said:
Titanium does work harden. CF degrades.
Click to expand...

Most of my work hardening nightmares are in Stainless. Comparatively Ti work hardens much less.

From my link.

A value called the Strain Hardening Exponent is one way to quantify the degree to which a material will work harden. Here’s a table showing the Strain Hardening Exponent (the n-value) for a number of common metals:

Material n

304 stainless steel (annealed) 0.45
Titanium, Ti-6Al-4V, annealed 20C 0.015
Titanium, Ti-6Al-4V, annealed 200C 0.026
Titanium, Ti-6Al-4V, annealed 600C 0.064
Titanium, Ti-6Al-4V, annealed 800C 0.146
Click to expand...

I have no idea if you could use the work hardening property to increase strength. I tink the work hardening would reduce toughness. That might be bad? Also might be negligible. Above my pay grade to say :laughing
 
NorCalAthlete said:
Might be a dumb question, but...

I recall one of the interesting tidbits about the SR71 construction (also titanium) was that it was specifically engineered in a way that leaked fuel on the ground, necessitating refueling immediately after takeoff, because the speeds / pressures / temperatures at cruising conditions would swell the metal to fill the gaps.

In theory...couldn't you do something in the reverse for a submarine? Ie, engineer it in a way that as the pressure builds, it actually gets stronger / more secure?

I feel like the sphere obviously works, but in this day and age of AI assisted tools, we may see some crazy bulbous / tetrahedron / whatever designs start getting tested with that principle in mind.
Click to expand...

that's a heat effect, not really applicable here though there would be some contraction of the materials as they get colder this is a finite amount. for it to be of any use the internal pressure would have to be equal to the external pressure to induce tension in the CF laminate

if one could find a method to do the opposite of pre-stressing concrete, that would be interesting. only thing i could come up with is pressurizing the inside, which is of course impossible because of the meat based passengers


Enchanter said:
The second vid in ctwo's post claims that the carbon fiber compressed a half inch more than the titanium at operational depths. I have no idea it that is true.

And because I'm that guy:
The SR-71 did leak, and it did require refueling immediately after takeoff. The SR-71 did not takeoff fully fueled because it would not be able to successfully abort the takeoff if there was an emergency due to the added weight of full tanks.
Click to expand...

the differential movement is a fact. i didn't check his numbers but they sound likely.

i haven't seen all the videos out there of course, people love to get really verbose about this incident and i'm about to do the same thing. the different rates with with which the rings and tube contract is partcularly bad right next to the joint where there is a slight overlap of the Ti onto the CF, if it were a weld it'd be the heat affected zone where you expect welds to break (just for visualization purposes i use that example, it's otherwise irrelevant)

with the Ti ring effectively not moving, and the center of the CF tube contracting significantly the loading on the glue joint puts a moment load into the skin of the CF tube, which tries to peel the tube apart separating the individual plies from the one next to it. Interlaminar Shear Strength is the name of the property, and it's generally orders of magnitude lower than in the preferential direction. I think that's the initial failure point and it wouldn't have been a pin hole, at least not for any measurable period of time

a similar situation contributed to the Challenger exclusion where the casing of the solid rocket booster was stiffer at the joints, which allowed a very slight rotation about that joint as the pressure inside built up. coupled with the cold o-rings inflexibility that couldn't keep things sealed and it let the hot gasses out.
 
Holeshot said:
Not dumb, but you're essentially talking about the inverse of pressurization in an airplane @ altitude, right?
Click to expand...

Yeah, this is sorta what I was getting at.

Not just the compression of the metal itself, but compression of the overall entire structure to form / improve seals or seat things together tighter to reinforce itself the deeper you go.

I'm trying to think of a good real-world example...compression lid on storage jars maybe? Where there's a rubber seal in between 2 pieces of glass, and then the metal latch providing that compression pressure to get a far better seal than if it was just stuck on there.

Or maybe more like the way certain glass bottles are designed to withstand drop tests...to an extent? Nah that's probably a bad example...

...I'm trying to think of something that fits this.
 
The better sealing at depth is what many cameras do and likely the view port on titan. You have an oring to seal at low pressure, then the pressure on the port pushing into the dome is where the high pressure sealing comes from. Thats why it seems dumb to bolt the dome to the tube, because you have all the pressure you need to seal that interface. You just need something simple to seal until the high pressure takes over.
 
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