[JDW1023]

> According to the BBC, the entire sub is bolted shut from the outside, so even if the vessel surfaces, the occupants cannot escape without outside assistance and could suffocate within the capsule.

Why is the submarine bolted shut from the outside?

[lisasays]

Assuming, quite reasonably, that there has to some kind of rationale for this -- I would guess it's because there's some significant structural complexity (and hence risk) involved in having it be open-able both ways.

[sschueller]

It makes no sense as the pressure would prevent you from opening it from the inside anyway until you are back on the surface.

[croes]

It makes sense if you want a simple construction. Bolting it from the outside is easier than an internal mechanism.

[bambax]

It would make a lot of sense if you're floating at the surface of the ocean and need air.

[vicktour]

The location of the door really doesn't allow it to be opened while its in the water. I would guess, as I have no evidence other than an untrained eye, that the window would either be fully underwater or at least partially underwater. It would sink if it was opened. Not to mention that they would need to equalize the pressure inside the sub to even push it open.

[ploika]

Bit of a tangent maybe, but according to some expert I heard on the radio this morning, it's a submersible and not a submarine precisely because the vehicle is so totally dependant on the support ship. That includes everything from communication to getting in and out.

[SoftTalker]

It's dependant on a support ship but it's not tethered to it? Maybe depth prohibits that?

[bagels]

Yes, this was my thought too. Titanic depth, I think, would not be too deep for steel cables to reel it back in, but marginally. It could also double as a communication link.

[the_gipsy]

There have been tethered submersions deeper than the titanic wreck.

[Strom]

I guess for the immense pressure you get at that depth. However an emergency release would still make sense.

[starkparker]

Naval submarine hatches rely on the pressure to keep the hatch shut. The water pressure outside is greater than the air pressure inside. The hatch locks around a sealing o-ring. Escape trunks are sealed off from the rest of the ship and work like an airlock. Deepsea Challenger's outward-opening hatch/egress trunk worked the same way; indeed, its view window was on the hatch.

[tzs]

> Naval submarine hatches rely on the pressure to keep the hatch shut

I don't remember which company it was, but there was an aircraft company that made the mistake of relying on screws instead of pressure to keep the cockpit windows in place.

The windows were installed from the outside with outside screws to hold them in place. During maintenance one of the windows got replaced and the worker accidentally used the wrong screws which were much weaker than the correct screws.

Next flight when the plane got high enough the difference between outside pressure and the higher pressure in the pressurize cabin blew the window out and one of the pilots got sucked out. Someone else in the cockpit was able to grab his legs on the way out and hold on keeping him from falling, although he spent the rest of the flight dangling out the window getting buffeted around pretty severely. The people left in the cockpit were sure the guy dangling out the window was dead, and they were having a hard time holding on, but they didn't want to lose his body and managed to keep him.

They also were having a hard time communicating with each other or with air traffic control because of the noise from the missing window.

They did get down safely, and the everyone's surprise found that the guy dangling in the window was alive, quite bruised, and had frostbite all over his face, but nothing permanent. He made a full recovery.

They redesigned the windows so on newer planes they installed from the inside with inside screws, whose job was now to keep the window from falling into the plane instead of keep it from falling out.

A "wrong screw" accident then might mean losing a window when taxiing or during takeoff or landing or at low altitude, before there is much pressure different between inside and outside. No one would be sucked out then and the noise would be a lot lower. At higher altitudes the pressure difference would be keeping the windows in place.

As I said I don't remember what company's plane had this accident. It was on one of those "air disaster" documentary shows.

[gcanyon]

I think this is the story you're talking about. The replacement windscreen bolts were too narrow: https://admiralcloudberg.medium.com/the-near-crash-of-britis...

[komadori]

It was BA flight 5390. Admiral Cloudberg has a good write-up: https://admiralcloudberg.medium.com/the-near-crash-of-britis...

[andrewmunsell]

But, as with airplane doors (but in the opposite direction), if the door was designed to open outwards then you couldn't open it under pressure no matter how hard you pushed

[Strom]

At those pressures I don't think you would want to open the door even if you could. I was more thinking about being at the surface and having nobody else to unbolt it from the outside.

[andrewmunsell]

Oh yes, I am (though I am absolutely not a real engineer nor do I have any experience with subs) just questioning why they would need to bolt it from the outside anyways. If it was to keep occupants in, I would imagine that a door that opens outwards would solve that issue if submerged, and would still be openable on the surface

[rightbyte]

It is a simpler design to screw the nuts from the outside. Otherwise the hull would need through hull screws attached to the door or some sort of clamp around the hull edge by the door opening.

[rsaxvc]

Guess: weight and cost savings

[shadowgovt]

An emergency release implies explosive bolts that could fail catastrophically at depth.

... which would be a risk that I might recommend for another application and manufacturer, but not for this firm, apparently. For this firm, I think I'd recommend "Don't do what you're doing, but if you must, keep it as simple as possible."

[tedunangst]

Is there enough room inside the sub to turn a long enough wrench to apply the appropriate torque?

[kumarvvr]

Because making reliable doors that are leak proof under enormous pressures is very very difficult.

[croes]

Easiest way to shut it?

[dist-epoch]

There is no point in allowing the door to be opened underwater since it doesn't have an airlock.

[gs17]

No one is proposing a literal "suicide door". But it makes sense to have it openable after surfacing, at least for emergencies.

[stickfigure]

"Surfacing" unassisted would mean floating with the top of the submarine at water level. You still won't be able to open the door.

[gs17]

That's possible. Then at least some form of ventilation usable after surfacing should have been included if you're locking people in.

[stickfigure]

Every thruhull is a potential source of death at 5000+ psi.

The bigger problem seems like underinvestment in "getting found" technology.

[93po]

There is 96 hours of oxygen onboard, and even without any supplement, 5 people would survive in a space that large for at least half a day with no fresh air