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Titanic tourist submersible goes missing with search under way

bbc.com

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Re: Titanic tourist submersible goes missing with search under way

#451

Post by xoxxala »

WalterBright wrote: post #375
kortex wrote: post #47

Earlier quoted context omitted.

I'm not really an engineer (general hobbyist, former chemist) but I have built and worked with pressure and vacuum vessels. Positive pressure (tank vs exterior) is much easier to deal with than negative pressure (vacuum vessel at 1 atm, or bathyscape with 1 atm inside and high pressure exterior). In positive pressure, your stress is mostly in the hoop mode, which is stable. This is why aluminum cans can be so thin. I…

In college, a popular showoff trick was to set an empty beer can on the floor. Then balance on it with one foot. If your balance was good and well centered, the can would not collapse. Then, for extra credit, slowly reach down and just tap the side of the can with a finger tip. The can would instantly crush to a disk. Extra karma points for crushing it into a perfect circle, rather than an oval. It would collapse so…

Bill Hammond, the Engineer Guy on youtube, has a video on the design and engineering of the aluminum can with a brief clip of someone standing on a can (around the 7-8 minute mark).

https://m.youtube.com/watch?v=hUhisi2FBuw

Re: Titanic tourist submersible goes missing with search under way

#452

Post by jojobas »

bagels wrote: post #356
varjag wrote: post #235

Earlier quoted context omitted.

It's traditional in deep submersibles design, dating back to bathysphere. You probably weren't hanging around when they were designing them

Tradition itself is probably the worst rationale for an engineering solution. Maybe it's the right way for other reasons?

Traditions emerge from "other reasons". There is probably not enough excess buoyancy to open the hatch without flooding, so without external support you're dead anyway.

Re: Titanic tourist submersible goes missing with search under way

#453

Post by brenainn »

moneywoes wrote: post #385
totallywrong wrote: post #348

I get the flex this affords, but I can't think of anything less appealing than spending 8 days underwater in a tiny capsule. I hope they're found and nothing happened.

I thought the trip was 8 hours

I was confused by the article as well. I believe it's eight days in total including the trip on the ship to get there and back. And then the actual dive is around 8 hours.

Re: Titanic tourist submersible goes missing with search under way

#454

Post by stickfigure »

fergbrain wrote: post #247
sclarisse wrote: post #231

Earlier quoted context omitted.

It’s pretty bad, but when the door accessible from the inside implodes from the insane pressure of the water around it, that’s even worse.

The door can still be designed to open outward and also able to be unlatched from the inside: those aren’t mutually exclusive properties.

It needs to remain perfectly watertight at over 5000psi or everyone dies. That design constraint probably eliminates most clever latch designs.

Re: Titanic tourist submersible goes missing with search under way

#455

Post by manarth »

fastball wrote: post #410
moffkalast wrote: post #315

Earlier quoted context omitted.

There are typically compressed air cylinders that can expel the water in case of emergency. At least on military submarines that go down to 300m, it may not work 4km down where the pressure is ridiculous. https://en.wikipedia.org/wiki/Emergency_main_ballast_tank_bl...

Yep, I believe it would be almost impossible to have air tanks that are pressurized enough to blow out water from ballast tanks at that depth.

Standard scuba cylinders are typically pressurised to around 230 bar, with a small proportion taking 300 bar as their standard working pressure (with margin for over-pressure).

It's not too much of a leap from there to the 380 bar pressure at Titanic's depth.

Re: Titanic tourist submersible goes missing with search under way

#456

Post by wombatpm »

jonathankoren wrote: post #180
ajessup wrote: post #100

Earlier quoted context omitted.

I love this line - one of my favorites of the show. Thanks for sharing.

And then JJ Abrams put Enterprise underwater, ostensibly to hide it from a stone age civilization. Such a hack. Ruined both of the biggest and beloved scifi franchisee. smh

I still have problems with Voyager and Enterprise landing at all. Besides the maxim that everything is airdroppable at least once.

Re: Titanic tourist submersible goes missing with search under way

#457

Post by camel_gopher »

scarnz wrote: post #289
minedwiz wrote: post #267

Earlier quoted context omitted.

Communicating with submarines is actually a nightmare. The saltwater ruins most radio communications, so you have no chance to receive GPS signals, which are pretty weak even on the surface. One thing the military does/did to communicate with subs is use low-bandwidth text-only very low frequency radio, but you need colossal transmitters and there's no way the mother ship carries one. Hydrophones are also an option,…

I concur. Message is authentic.

Message is authentic. Set condition 1-SQ.

Re: Titanic tourist submersible goes missing with search under way

#458

Post by [deleted] »

spaceguillotine wrote: post #190
jonathankoren wrote: post #178

Earlier quoted context omitted.

Jesus. This sounds like this group is just taking billionaires' money while running a death trap. How the hell do you lose your sub for five hours? This should have stopped all trips until they fixed this problem through a combination of technical and procedural changes.

when you put it like that i'm suddenly pro death trap

[deleted]

Re: Titanic tourist submersible goes missing with search under way

#459

Post by stickfigure »

jonathankoren wrote: post #180
ajessup wrote: post #100

Earlier quoted context omitted.

I love this line - one of my favorites of the show. Thanks for sharing.

And then JJ Abrams put Enterprise underwater, ostensibly to hide it from a stone age civilization. Such a hack. Ruined both of the biggest and beloved scifi franchisee. smh

A series with teleporters, time travel, warp drive, artificial gravity, deflector shields, all manner of ESP-type woo... and submerging a spacecraft is what ruins it for you?

Re: Titanic tourist submersible goes missing with search under way

#460

Post by waste_monk »

system2 wrote: post #386
rajnathani wrote: post #83

For those mentioning about detailed location tracking / communication: Non-low-bandwidth communication underwater is really difficult due to the physics of EM waves traveling through a medium such as water: https://en.m.wikipedia.org/wiki/Underwater_acoustic_communic...

Why not sonar then?

If you mean "why aren't they using sonar to locate the missing vessel", I'm sure they're trying. One of the articles about this event I saw mentioned a P-8 Poseidon being deployed to assist the search. I would be extremely surprised if at least a few sonobouys hadn't been deployed.

If you're asking why they don't have a acoustic phone for underwater communications, I couldn't tell you. As I understand the Janus digital underwater communications standard (which as I understand is an open standard and is also standardised as NATO STANAG 4748, so search vessels should be able to understand it) range is about 28km [1], not sure about purely analogue implementations, but some solution should be easily achievable for any entity capable of building the submarine in the first place. Maybe they simply elected not to install one? or maybe the sub is drifting and the search area is too large to reliably establish communications.

They seem to have a "move fast and break things" approach and declined to get their vessel "classed" [2] as they claim to be too innovative to follow industry standards for such things... does not bode well for the missing vessel.

[1] https://en.wikipedia.org/wiki/Underwater_acoustic_communicat...

[2] https://oceangate.com/news-and-media/blog/2019-0221-why-tita...

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