Titanic tourist sub missing

IsThisTheLife said:
"Shallower diving subs"? What relevance do they have? Are you really going to give any credence to Oceangate's assertion that no other deep-water submersible has been built with anything but a spherical cabin because of 'conservatism'?
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It doesn't matter what Oceangate says.
It is possible to make a vessel resisting pressure at 4km which is not spherical. It's just a matter of getting wall thickness from well understood formulas. It might be too heavy if made from steel, or even titanium. It might need large lifting tank, similar to Trieste. It might be impractical, and expensive. And it would be revolutionary in deep diving submersibles. But it will be done one day, I'm sure. Even using carbon fiber, as at the moment it seems to be the only practical choice.
But it has to be done properly.
 
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I think this does demonstrate why sometimes regulation and standards can be a good thing.

This should have been still in a prototyping stage, it wasn't ready for full time service, and we now know why they avoided the many safety bodies, their work wasn't up to it.

I think it's a good idea i.e. to try and develop cheaper, less resource intensive platforms. They shouldn't be criticized for that. But given that the outcome of failure is pretty much guaranteed to be death any new approach to building such subs should be painstakingly researched, designed, manufactured and tested. All steps that they missed out.
 
TurkeysGhost said:
Silicon valley brain tends not to work great when you're interacting with physical forces that can turn the human body into jelly.

But yeah, this galaxy brain guy piloting his death trap does give us a bit insight into his mental state. Hard to say this guy was cynical since he believed in the tech enough to put his own life on the line. Idiotic, but respectable in some way, though roping in other people into his deathtrap is harder to admire.
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That's a good point, and one that actually goes pretty far back. There's a decades-old joke from the heyday of Moore's Law that went something like: "If automotive technology advanced like desktop computer technology, cars today would go 5,000 miles an hour, get 2,000 miles to the gallon, cost $295.00... and every couple of days, they'd explode."

What happened was that a submersible that was designed, tested, and deployed like software reached it's "and then it would ex[im]plode" point.
 
Dr.Sid said:
It doesn't matter what Oceangate says.
It is possible to make a vessel resisting pressure at 4km which is not spherical. It's just a matter of getting wall thickness from well understood formulas. It might be too heavy if made from steel, or even titanium. It might need large lifting tank, similar to Trieste. It might be impractical, and expensive. And it would be revolutionary in deep diving submersibles. But it will be done one day, I'm sure. Even using carbon fiber, as at the moment it seems to be the only practical choice.
But it has to be done properly.
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Indeed. I've yet to hear any engineers state that the submersible failed because of it's size. They've blamed the construction methods used to achieve that size within a budget. I've no doubt that vessels capable of carrying five or more people will eventually be built and operated safely, but to build one with today's established methods would have cost much more than Rush was willing to pay.
 
Darat said:
I think this does demonstrate why sometimes regulation and standards can be a good thing.

This should have been still in a prototyping stage, it wasn't ready for full time service, and we now know why they avoided the many safety bodies, their work wasn't up to it.

I think it's a good idea i.e. to try and develop cheaper, less resource intensive platforms. They shouldn't be criticized for that. But given that the outcome of failure is pretty much guaranteed to be death any new approach to building such subs should be painstakingly researched, designed, manufactured and tested. All steps that they missed out.
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In recent conversations with both my engineer wife and joobz (a chemical engineering professor), they've both said that if there's one good thing to come from this tragedy, it's that it has given engineering professors all over the world something to show their students as an example of why safety matters.
 
Interesting approach is US Navy DSRV. It's designed for depths up to 1500m, so it sits between military subs and deep-sea vehicles. Unlike research vessels, it's also designed to carry passengers. Up to 24 (+2 crew).
It uses 3 spheres joined together, instead of tube with domes. Sure, the integrity of the spheres is weakened by the holes which connect them, but that hole can be relatively small, just to allow one person to pass, and IIRC there is extra stiffener ring.

Simple diagram here: https://alchetron.com/Deep-submergence-rescue-vehicle
 
Dr.Sid said:
Interesting approach is US Navy DSRV. It's designed for depths up to 1500m, so it sits between military subs and deep-sea vehicles. Unlike research vessels, it's also designed to carry passengers. Up to 24 (+2 crew).
It uses 3 spheres joined together, instead of tube with domes. Sure, the integrity of the spheres is weakened by the holes which connect them, but that hole can be relatively small, just to allow one person to pass, and IIRC there is extra stiffener ring.

Simple diagram here: https://alchetron.com/Deep-submergence-rescue-vehicle
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As far as I can see from the description in your link it works on the diving-bell principle. If so, that is an entirely different matter. In a diving bell, you have the same pressure inside as outside, so you can have an open water surface. This is useful for rescue purposes, as these crafts seem to be designed for.

1500 meters is rather deep for a diving bell, though. There will be some VERY interesting compression/decompression challenges.

Hans

Hans
 
MRC_Hans said:
As far as I can see from the description in your link it works on the diving-bell principle. If so, that is an entirely different matter. In a diving bell, you have the same pressure inside as outside, so you can have an open water surface. This is useful for rescue purposes, as these crafts seem to be designed for.

1500 meters is rather deep for a diving bell, though. There will be some VERY interesting compression/decompression challenges.

Hans

Hans
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It will recover to a diving support vessel that has areas pressurised to the same depth I would think
Any depressurisation will be done aboard ship like any other saturation diving.

US Navy dive manual and tables are used as the standard throughout the industry, they know what they are doing.

https://www.divetable.info/workshop/USN_Rev7_Tables.pdf
 
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MRC_Hans said:
Ah, but I fully agree.

The takeaway from this, in as much as that ought to come to a surprise to anybody, is that you can make low-cost designs and you can make innovative design, but if there are serious safety concerns, you can't do both:

Either you save by using well proven standard components (if such exist in the deep-sea business) and -methods, or you try and test every new idea you implement.

Hans
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Sure, test away, but not with passengers aboard! That is just irresponsible.
 
Andy_Ross said:
It will recover to a diving support vessel that has areas pressurised to the same depth I would think
Any depressurisation will be done aboard ship like any other saturation diving.
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Yes, and that is probably the reason for the spheres: It will be able to retain a high pressure inside during transfer of rescued crew who will probably have spent some considerable time under pressure, and thus will need a lengthy decompression period.

Hans
 
Myriad said:
That's a good point, and one that actually goes pretty far back. There's a decades-old joke from the heyday of Moore's Law that went something like: "If automotive technology advanced like desktop computer technology, cars today would go 5,000 miles an hour, get 2,000 miles to the gallon, cost $295.00... and every couple of days, they'd explode."

What happened was that a submersible that was designed, tested, and deployed like software reached it's "and then it would ex[im]plode" point.
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Well, that was the Pinto and now some lithium battery cars!

ETA: We had a Pinto at that time and scared the b’jezuz out of me whenever someone was tailgating.
 
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If Rush had actually used "aerospace" principles rather than marine (as he grandiosely claimed) in manufacturing this death trap, the "tube" would have been more than a glorified toilet-roll of CF.

Perhaps an ellipsoid with multi-directional CF weave.

But then imagine the cost of such a thing, and it's no surprise that no-one (so far) has attempted anything like it.
 
MRC_Hans said:
As far as I can see from the description in your link it works on the diving-bell principle. If so, that is an entirely different matter. In a diving bell, you have the same pressure inside as outside, so you can have an open water surface. This is useful for rescue purposes, as these crafts seem to be designed for.

1500 meters is rather deep for a diving bell, though. There will be some VERY interesting compression/decompression challenges.

Hans

Hans
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I think it's some kind of misunderstanding. DSRV has to equalize with sub it's rescuing people from. That might be above 1 atm, if they took some water .. but it also might be just original 1 atm. The pressure inside won't be much over 5 atmospheres, as nitrogen becomes toxic after that. Certainly at 1500 m depth, nobody would be alive inside if the sub was open to the sea.

DSRV would dive, dock, ideally communicate with the crew inside, increase pressure inside DSRV as needed, open hatches, transfer crew.
Decompression might still be an issue, but the hull of DSRV still has to stand to 150 atm of pressure.
Increasing pressure inside DSRV let's say to 5 atm would decrease the load on the hull .. but at 1500m it wouldn't make much difference. But it would indeed allow DSRV to work as diving bell in shallow depths, which still might be useful.
 
The more I look into this, the more it appears that the problem of differential expansion and contraction between titanium end caps and a carbon fiber cylinder isn't actually solvable. You certainly wouldn't want to use a joint that slides or flexes. Even if you could come up with an expansion joint that can hold out the pressure, which I'm pretty sure you can't, you might as well forget the CF and Ti and make the whole craft out of that expansion-joint material.

Stronger adhesion (mechanical mixing and application in a clean room, vacuum treatment to remove bubbles, autoclaving to cure the adhesive, etc.) would probably have helped the submersible last longer but I can't see that alone preventing the differential expansion from crumbling the CF over time.
 
IsThisTheLife said:
If Rush had actually used "aerospace" principles rather than marine (as he grandiosely claimed) in manufacturing this death trap, the "tube" would have been more than a glorified toilet-roll of CF.

Perhaps an ellipsoid with multi-directional CF weave.

But then imagine the cost of such a thing, and it's no surprise that no-one (so far) has attempted anything like it.
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Another reason why SpaceX ditched the idea of using composites in the construction of BFR (Starship), although they do use a COPV (pressurized to 6,000 psi) in Falcon 9's second stage as a helium tank for pressurization of propellant tanks.
 
smartcooky said:
Another reason why SpaceX ditched the idea of using composites in the construction of BFR (Starship), although they do use a COPV (pressurized to 6,000 psi) in Falcon 9's second stage as a helium tank for pressurization of propellant tanks.
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The accomplishments with composites in aerospace are pretty astounding to me (watching a 787's wings flex), I just hope they prove to be as robust as the aluminium alloys that have been used so successfully for the last 90 years or so.
 
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