Humor Random Comments Thread

[n72.75]

No cardboard, no cardboard derivatives (like paper), no string, no cellotape...very rigorous maritime engineering standards are needed.

And obviously the front's not supposed to fall off.

 

[Urwumpe]

Why what?

Why do I want to know? Because I have enough curiosity to rip all 9 lives from a million cats.

Well, why does it make a difference for you, if the initial collapse is dry or if the pressure is equalizing faster by fluid flow overtaking the hull?

 

[jedidia]

...no cellotape..

Awww common, how am I supposed to build anything without that? Surely Gaffa-tape is fine though?

 

[Linguofreak]

And obviously the front's not supposed to fall off.

Don't worry, it didn't. The front separated too quickly for gravity to be a factor.

 

[Linguofreak]

Well, why does it make a difference for you, if the initial collapse is dry or if the pressure is equalizing faster by fluid flow overtaking the hull?

None whatsoever, in terms of any likely applicability to my own life. But a situation doesn't have to be applicable to you for its dynamics to be interesting.

 

[Urwumpe]

None whatsoever, in terms of any likely applicability to my own life. But a situation doesn't have to be applicable to you for its dynamics to be interesting.

Well, likely it is something that depends on the actual case.

I now think, they have winded the pressure hull the wrong way to start with. The fibers are great with expansion, not compression, so the pressure forces acting on the hull should be turned into stretching the fibers, for example by prestressing the hull with an exoskeleton.

 

[N_Molson]

No cardboard, no cardboard derivatives (like paper), no string, no cellotape...very rigorous maritime engineering standards are needed.

Read (from an USN document) that if you make a cylindrical hull that deviates from being a perfect cylinder by more of 0.5%, up to 35% of the hull strenght is compromised. Yes, it means that very few shipyards in the world can build those vehicles. The same document makes the list of the shipyards in the US that have the certification, there are no more than 4 or 5 of them. In fact, the constraints 4 km under the ocean surface are much more severe than in space, where the pressure differential between inside and outside the hull is at worst of 1 atm.

 

[GLS]

More knowledge being dropped:

No cardboard, no cardboard derivatives (like paper), no string, no cellotape...very rigorous maritime engineering standards are needed.

And obviously the front's not supposed to fall off.

For the ones who didn't get the references:

 

[TheShuttleExperience]

Very good docu from 1998. Sadly only in German. But gives a very good impression of what it was like to perform a professional dive with the Mir down to the Titanic.

The trip starts at 28 minutes.

It's almost like space flight but just without zero gravity. Also interesting how the commander changed the Co2 filter because the first one was depleted and the air already got bad. At least he didn't have to use socks and Duck Tape...

All in all this already looks like professional, proven and well certified technology compared to the Titan. And it was 25 years ago...

 

[n72.75]

There was a short clip in an old news article on the Titan that showed a large filament would structure being made. I don't know if that was a video of the Titan being made or just a representative clip or even an un-related clip thrown in as filler.

Assuming it was an actual clip of the actual Titan, I think it's a pretty safe bet that someone conflated the mechanics of internal pressure vessels with external pressure vessels as was previously stated here.

It probably would've been stronger and lighter to just take the CF out and just cast the hull out of the epoxy matrix material. (Not really, but in a sense that's all that's providing a significant portion of the force holding up two miles of ocean, it's just glueing a bunch of thin shells together with the entire ocean trying to roll them up).


My senior design project in college involved a high level design of an electric aircraft. It was a comaborative effort between about 20 engineering students (in competition with another 20ish). Iirc in 2012 we chose NOT to go with a composite wing spar (simple (ish) bending loading, vs complex compressive loading) simply because we couldn't find good literature on endurance limits.

I encountered this a lot in the synthetic rope/textiles world too but: all we know about steel comes from many many many hard lessons learned in the 18th, 19th, and 20th centuries. There is no shortcut to relearning those with a new material that's been around since the 80s. There is a long list of hard lessons won in early GF and CF sailboats. I wonder if any of the engineers were aware of those. Something makes me think no.

 

[MaxBuzz]

creator interview Mir
The cause of the tragedy that occurred with the bathyscaphe "Titan" could be the use of carbon fiber for the manufacture of the main body, said an oceanologist, creator of the deep-sea submersibles "Mir-1" and "Mir-2" Anatoly Sagalevich. In a conversation with KP.RU, he emphasized that this material is very fragile and does not bend under loads, but bursts like glass. According to the expert, the creators of the bathyscaphe neglected elementary rules.

....further down the article is swearing....

 

[Thunder Chicken]

I now think, they have winded the pressure hull the wrong way to start with. The fibers are great with expansion, not compression, so the pressure forces acting on the hull should be turned into stretching the fibers, for example by prestressing the hull with an exoskeleton.

This would put a compressive pre-load on the polymer matrix. This would make things worse if you put the vessel under external pressure.

 

[n72.75]

The only correct way to do a composite submarine is to put the high pressure ocean on the inside and the air on the outside. IMHO

 

[Thunder Chicken]

The only correct way to do a composite submarine is to put the high pressure ocean on the inside and the air on the outside. IMHO

If you use Earth's gravity you don't need a submarine; it does this automatically.

 

[Urwumpe]

This would put a compressive pre-load on the polymer matrix. This would make things worse if you put the vessel under external pressure.

Not on the polymer - the exoskeleton. Like the Atlas rockets, when they are transported, same problem. As long as the tank pressure is too low for preventing buckling, it was kept stretched by a pulling front end and aft end apart.

 

[jedidia]

I used to be professionally involved with understanding failure modes in textiles

Now all I can think of is "wardrobe malfunction"... :lol:

Assuming it was an actual clip of the actual Titan, I think it's a pretty safe bet that someone conflated the mechanics of internal pressure vessels with external pressure vessels as was previously stated here.

That would be truly mindbogling, though. I mean, I am aware of those differences, and the sole education I have in a remotely egineering-related field is an apprenticeship as a toolmaker, and even I am perfectly aware of that difference (conceptually. You'd probably have to give me a couple days to do the math...). How could an actual engineer, much worse a group of them, make such an elementary mistake? It doesn't seem possible...

 

[Thunder Chicken]

How could an actual engineer, much worse a group of them, make such an elementary mistake? It doesn't seem possible...

This happens when your non-engineer CEO exhibiting the Dunning-Kruger effect decides that CFRP is the right answer and fires all the experienced engineers that disagree.

 

[jedidia]

and fires all the experienced engineers that disagree.

Yes, but... even the inexperienced ones should disagree, shouldn't they? At least if the CEOs problem is as obvious as "confused internal and external pressure". It just seems a mistake too elementary to make if there are any engineers around.

 

[Thunder Chicken]

Yes, but... even the inexperienced ones should disagree, shouldn't they? At least if the CEOs problem is as obvious as "confused internal and external pressure". It just seems a mistake too elementary to make if there are any engineers around.

Ideally yes, and maybe some did. But now you are pushing a moral decision on inexperienced engineers that may begin to doubt themselves and their work, and without the support of experienced engineers and external regulation they either quit the company or try to figure out a way to make it work. In these instances the CEO will simply continue to intimidate and fire people who disagree, and hire on more people until he winnows out all dissent and he has nothing but weak, timid engineers willing to say 4 = 5 to please him.

This is what you get when you have a CEO who thinks they are the smartest person in every room they enter on any subject.

 

[Urwumpe]

This is what you get when you have a CEO who thinks they are the smartest person in every room they enter on any subject.

Well, now he looks not so smart.

Also, any sane engineer would run away, with liability wavers like that, no structural analysis or testing or certification. It was a suicide pact, and I don't think any engineer will like to have his name on this.