[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?

[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.

[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

[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.