Titanic tourist submersible goes missing with search under way • Hacker News Board

Re: Titanic tourist submersible goes missing with search under way

#551

Post by hkchad » Tue, Jun 20, 2023, 3:22 PM UTC

zarzavat wrote: post #490

hkchad wrote: post #442

Earlier quoted context omitted.

Tourist Cave diver here, kicking up a little dirt happens on almost every dive, we train to deal with complete blackout scenarios, while sharing air, in restrictions but that rarely happens. Typical incidents relate to people doing a dive over their experience level or getting lost and running out of gas. Some cave systems are truly huge in scale and navigation can be difficult if you do a huge dive in one go. Person…

Honest question, why do it? What’s the attraction of cave diving? Are underwater caves exciting enough that it’s worth the risk? Or is the risk itself the main thrill? Or is your perception that it’s not that risky? I can understand the attraction of e.g. wingsuits, because the idea of flying like a bird is compelling, even if I would never risk my own life to do it. Although there’s definitely more than a few wingsu…

Personally I do it because it's the closest I will ever get to feeling like a space explorer. You are neutrally buoyant (weightless) completely relying on your equipment for survival and able to see places IN the earth very few people will ever experience, plus I love a challenge. When most people think of cave diving they imagine really small holes and limited visibility. Sure, that can be it if you want or you can visit places like this,

https://youtu.be/TTICP6m-FyY?t=594

^ THAT is why I do it. Also I spent about 2 years in initial training and continue to train every time I dive. Our goal is to drive the risk to 0 which isn't reality but I feel less safe driving to some of the caves than I do diving them.

Re: Titanic tourist submersible goes missing with search under way

#552

Post by fastball » Tue, Jun 20, 2023, 3:28 PM UTC

manarth wrote: post #546

fastball wrote: post #521

Earlier quoted context omitted.

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 dyn…

> If they had a method to keep 382 bar of water dynamically out of the ballast tanks By filling the ballast tanks with 382 bar of air. The human-interior of the sub is maintained at 1 bar to avoid compression demands (hyperoxic seizure triggers at approx 7.6 bar when breathing atmospheric gases; HPNS (High Pressure Nervous Syndrome) is common after 16 bar on a helium-oxygen mix), and decompression requirements. Equal…

I think you may have led me astray with that first comment, and that my intuition was probably correct. How exactly does one purge the ballast tank with the air tank? Would you not actually need an air tank that has (at least) double the pressure of the outside water? Then to clear the ballast tank you would open the air tank, the higher pressure air would then force out the lower pressure water (this is clearly why it can't be the same pressure as implied in your first comment), and then when you're done you have two tanks (your air and ballast tanks) both at 380 bar, assuming they are both the same volume.

In that case you'd actually need a PV rated for 740 bar, which seems outside our current materials science abilities. In fact (and I'm still mostly just spitballing here, not actually doing any math), I assume you actually need a purge tank with a pressure much greater than 2x, otherwise you're just cancelling out your ballast with your air tank, right?

That would track with using this system in submersibles that are operating at ~300m and not for things like this which are trying to operate at 4000m. At 300m you could have a 400 bar COPV for emergency purging that is only 7.5% the size of the ballast tanks, which sounds practical.

Re: Titanic tourist submersible goes missing with search under way

#553

Post by mustacheemperor » Tue, Jun 20, 2023, 3:30 PM UTC

jacquesm wrote: post #292

patrec wrote: post #282

Earlier quoted context omitted.

In what scenario would not being sealed from the outside make a positive difference? If they managed to surface, how would being able to "get out" in the middle of the ocean be helpful? If they didn't manage to surface, under what circumstances would have opening the hatch helped?

Air.

I think part of the issue there is designing a hatch that can be opened on the surface to exchange air without immediately swamping the sub in the sea chop. Alvin sank very fast when it was accidentally dropped into the water with the hatch open.

Re: Titanic tourist submersible goes missing with search under way

#554

Post by mannykannot » Tue, Jun 20, 2023, 3:38 PM UTC

carbine wrote: post #345

opwieurposiu wrote: post #197

Earlier quoted context omitted.

The hatch is bolted shut from the outside. When you make it back to the surface, there is no way to get out without external support. If the mother ship can not find the sub the occupants could be trapped bobbing just below the surface until their air runs out.

According to David Pogue (journo who did a dive on this vessel last year), at least as of last year there was no beacon to transmit location. One would hope radio would be working, in that case. Source: https://twitter.com/Pogue/status/1670826522138091521?s=20

I wonder if it at least had a radar reflector. This area of the Atlantic is notorious for fog, on account of the current which brought the iceberg there mixing with the 'Gulf Stream' (more formally known as the North Atlantic Drift at this latitude.)

Re: Titanic tourist submersible goes missing with search under way

#555

Post by mannykannot » Tue, Jun 20, 2023, 3:43 PM UTC

ra wrote: post #192

zh3 wrote: post #101

Earlier quoted context omitted.

I imagine the search and rescue effort have checked the seismograph/ocean sounds/other networks, AIUI an implosion at depth makes quite a bang, so not detecting one would be a positive.

Yeah, and you would have thought that in calm weather there would have been something to see on the surface. I hope they're OK.

It is a notoriously foggy area. I hope it at least has a radar reflector.

Re: Titanic tourist submersible goes missing with search under way

#556

Post by delfinom » Tue, Jun 20, 2023, 3:56 PM UTC

krisoft wrote: post #476

gremlinunderway wrote: post #230

Earlier quoted context omitted.

> As opposed to the professionals who went with a microsoft xbox controller? I think what's more telling is that they didn't even splurge on the actual Microsoft Xbox controller. They cheaped out with an unproven logitech gamepad. When you're already doing something in an unorthodox way at least don't half-ass it. > The company in question might be full of jokers, but your points don’t quite illistrate this well. The…

> Your distinction is a bit arbitrary. Every point about this company will always be about appearances unless you have first-hand accounts or experiences. Not really. Here is a substance based argument: there is no underwater FAA. This company, and any other private submarine company is setting their own quality level and then marking their own homework to see if they have met it. In a commercial environment they are…

>In a commercial environment they are incentivised to cut corners and there is no external force resisting this

Please if you are incentivized to cut $10 on the main control interface of your expensive sub that is incredibly low volume production, you have some fundamental cultural problems and its not a business decision.

Re: Titanic tourist submersible goes missing with search under way

#557

Post by delfinom » Tue, Jun 20, 2023, 3:56 PM UTC

krisoft wrote: post #476

gremlinunderway wrote: post #230

Earlier quoted context omitted.

> As opposed to the professionals who went with a microsoft xbox controller? I think what's more telling is that they didn't even splurge on the actual Microsoft Xbox controller. They cheaped out with an unproven logitech gamepad. When you're already doing something in an unorthodox way at least don't half-ass it. > The company in question might be full of jokers, but your points don’t quite illistrate this well. The…

> Your distinction is a bit arbitrary. Every point about this company will always be about appearances unless you have first-hand accounts or experiences. Not really. Here is a substance based argument: there is no underwater FAA. This company, and any other private submarine company is setting their own quality level and then marking their own homework to see if they have met it. In a commercial environment they are…

>In a commercial environment they are incentivised to cut corners and there is no external force resisting this

Please if you are incentivized to cut $10 on the main control interface of your expensive sub that also is to drive your business, you have some fundamental cultural problems beyond "commercial environment".

Re: Titanic tourist submersible goes missing with search under way

#558

Post by varjag » Tue, Jun 20, 2023, 4:15 PM UTC

gizmo wrote: post #503

varjag wrote: post #501

Earlier quoted context omitted.

If you pass out, how do they get you out?

Two hatches? One opens from the inside one opens from the outside? I'm sure there are other solutions. But as somebody else already pointed out: even if you get out in the middle of the ocean you're in real trouble, which makes the hatch issue kind of moot.

And that's twice the sealing surface to potentially fail.

Re: Titanic tourist submersible goes missing with search under way

#559

Post by mariuolo » Tue, Jun 20, 2023, 4:25 PM UTC

dheera wrote: post #259

opwieurposiu wrote: post #197

Earlier quoted context omitted.

The hatch is bolted shut from the outside. When you make it back to the surface, there is no way to get out without external support. If the mother ship can not find the sub the occupants could be trapped bobbing just below the surface until their air runs out.

Could they just have some drills with diamond-tipped bits stored inside for emergency use? If needed, drill through the whole shell, stick an arm out and unbolt from the outside. Or maybe a jackhammer to just hammer through whatever glass is there for observation purposes.

> Could they just have some drills with diamond-tipped bits stored inside for emergency use? If needed, drill through the whole shell, stick an arm out and unbolt from the outside.

A shaped charge might be a more sensible solution, but it's still within incredibly dangerous territory.

Re: Titanic tourist submersible goes missing with search under way

#560

Post by nradov » Tue, Jun 20, 2023, 4:52 PM UTC

zarzavat wrote: post #490

hkchad wrote: post #442

Earlier quoted context omitted.

Tourist Cave diver here, kicking up a little dirt happens on almost every dive, we train to deal with complete blackout scenarios, while sharing air, in restrictions but that rarely happens. Typical incidents relate to people doing a dive over their experience level or getting lost and running out of gas. Some cave systems are truly huge in scale and navigation can be difficult if you do a huge dive in one go. Person…

Honest question, why do it? What’s the attraction of cave diving? Are underwater caves exciting enough that it’s worth the risk? Or is the risk itself the main thrill? Or is your perception that it’s not that risky? I can understand the attraction of e.g. wingsuits, because the idea of flying like a bird is compelling, even if I would never risk my own life to do it. Although there’s definitely more than a few wingsu…

I am not a cave diver myself, but I do a lot of scuba diving and am friends with cave divers. Cave diving is one of the only remaining ways where an ordinary middle-class person can do original exploration without being part of some bigger organization. They can just get together with a few friends, fly to Mexico or wherever, and potentially go where no human has ever gone before.