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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

#521

Post by fastball »

manarth wrote: post #455
fastball wrote: post #410

Earlier quoted context omitted.

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.

Indeed, this company[1] seems to sell COPV's that are rated for 414 bar, so my assumptions were wrong in this case.

As such, I will revise my theory, and posit that the actual issue with this strategy at Titanic depths is keeping the water out of the ballast tanks once you've evacuated them. This seems plausible given that the hatch must be bolted on from the outside. If they had a method to keep 382 bar of water dynamically out of the ballast tanks, presumably they could use that same method to have a hatch that can be opened without manual screwing.

[1] https://steelheadcomposites.com/composite-pressure-vessels/

Re: Titanic tourist submersible goes missing with search under way

#523

Post by HKH2 »

TechBro8615 wrote: post #447
HKH2 wrote: post #441

Earlier quoted context omitted.

Surely if they slowly run out of air they won't be fully conscious when there is none.

Yeah I suppose that would be the ideal outcome. I was thinking of some kind of depressurization scenarios where they get crushed by 300 atmospheres worth of pressure.

Wouldn't that be much faster than drowning though?

Re: Titanic tourist submersible goes missing with search under way

#524

Post by beowulfey »

ciguy wrote: post #99

This section from their website is interesting: "Real-Time Health Monitoring The most significant innovation is the proprietary real-time hull health monitoring (RTM) system. Titan is the only manned submersible to employ an integrated real-time health monitoring system. Utilizing co-located acoustic sensors and strain gauges throughout the pressure boundary, the RTM system makes it possible to analyze the effects of…

> "No other submersible currently utilizes real-time monitoring to monitor hull health during a dive. We want to know why. Classed subs are only required to undergo depth validation every three years, whereas our RTM system validates the integrity of the hull on each and every dive." [1]

I suspect your intuition may be why RTM is not really used. Failures happen too quickly for them to give useful preventative data, perhaps?

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

Re: Titanic tourist submersible goes missing with search under way

#525

Post by closewith »

snaily wrote: post #474
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,…

There's at least one commercial acoustic underwater modem provider - Subnero out of Singapore. They claim up to 5km range: https://subnero.com/products/modem.html

> 4 km of communication range (horizontal) in littoral waters

Probably much lower range vertically.

Re: Titanic tourist submersible goes missing with search under way

#526

Post by closewith »

Prickle wrote: post #314
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,…

Military submarines also have a towed communications buoy that they can use to communicate with satellites. But that thing is connected to the submersible via a cable.

Even then, ELF is only available down to depths of hundreds of metres, not kilometres.

Re: Titanic tourist submersible goes missing with search under way

#527

Post by nickmcc »

mannykannot wrote: post #107
imglorp wrote: post #53

Earlier quoted context omitted.

A location pinger would be a no brainer but like you say, it only helps if there's another sub with a grapple in range, in time. I understand why oceanographers /might/ want to do this, but not in person when ROV tech is so good now, for biology and tourism. There are so many things that can happen to fragile humans in that complex machine: drowning, freezing, asphyxiating, crushing, oxygen narcosis, nitrogen narcosi…

Not that it appeals to me, but I would guess that the appeal of the Titanic lies in it being the canonical 'technological hubris' story and a contender in the 'if only...' category.

“I cannot conceive of any vital disaster happening to this vessel,” said Captain Edward Smith, commander of the Titanic.

Re: Titanic tourist submersible goes missing with search under way

#528

Post by belorn »

tim333 wrote: post #511
belorn wrote: post #367

Earlier quoted context omitted.

There is a relative recent trend by fire fighters to replace old steel/aluminum cylinders with breathing gas to cylinders made out of carbon (300 bar). They are also used under water in diving. The intend benefit is the reduced weight, but I wonder a bit how the failure mode might be a bit different from steel.

People deal with potential gas cylinder failure by occasionally testing them at higher than their usual pressure. You fill them with water and pressure to say 350 bar rather than 300. At least that's what they do with scuba tanks. Even if designed well they can be dropped, corroded etc. Not sure it's practical to do that with subs.

Yes, that is what they do with steel and aluminum cylinders. After over pressuring them you measure how much the metal flex, and that way you get an indication of how much fatigue and thus risk there is with that cylinders.

I am unsure if they do that with carbon versions. Do they flex with over pressuring, and is that flexing indicative to failure? If they do fail, is it like an explosion where the whole thing just unwrap, or is it more like a leak?

Re: Titanic tourist submersible goes missing with search under way

#529

Post by dredmorbius »

pfdietz wrote: post #424
dredmorbius wrote: post #343

Earlier quoted context omitted.

NB: Aluminium is rather notorious for its tendency to develop invisible hairline fractures which fail suddenly. Particularly around high-stress regions. The BOAC Comet failures (cracks propagating from squared-off window corners) is a notorious example, with multiple total hull losses in flight. I've experienced somewhat less significant failures of bicycle components (though they could easily have proved far worse).…

The window corner thing is an urban legend. https://www.youtube.com/watch?v=-DjnG74DDno The cracks actually started on the top of the plane, at cutouts for radio antennas. The windows always had rounded corners (although they made them even rounder later, which may have led to the confusion.)

Interesting, and a good explanation from Mentour Pilot as well.

Thanks!

Re: Titanic tourist submersible goes missing with search under way

#530

Post by l3mure »

svnt wrote: post #127
svnt wrote: post #124

Earlier quoted context omitted.

Oh it keeps going at 3:30: [CEO gestures at interior lighting] “I got these from… Camper World.” “We run the whole thing from this game controller.” [shows some knockoff controller]

I found the (wireless, $30) game controller: https://www.amazon.com/Logitech-Wireless-Nano-Receiver-Contr... and this from a review: “Pretty good controller, fits in hand comfortably and is compatible with anything I throw at it in a Debian linux environment. The conductive pads are extremely low quality though as I've had to replace them 3 times in the 2 years Ive been using it. For a Logitech product I expect bette…

Using a wireless controller for this is so funny, we need more grifters like them.
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