231–240 of 649 posts
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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.
Seems like a pretty stupid design if you ask me
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Yeah, the article is light on details. We don't know if they sank or if they're adrift on the surface somewhere after some failure. If they experienced an emergency underwater and were not able to surface, I'd fear for the absolute worst. People can survive in sunken submarines long enough to be rescued, but those are typically large submarines with multiple rooms that they can seal themselves off in. I doubt a touri…
If the sub was designed like a few other deep-sea craft I've looked at, they'd have positive buoyancy and weights to overcome this; the idea being that having to blow ballast tanks at 400 bar pressure differential is rather inconvenient and failure prone. Instead, the weights (attached with electromagnets) are simply jettisoned when it is time to recover to the surface and off you go. The upside to such a simple syst…
From: https://www.forbes.com/sites/katherinehamilton/2023/06/19/he...
"Pogue also shows the vessel uses construction pipes as ballast."
I'm having trouble finding the interview video, but dropping ballast involves the crew and passengers rocking the vessel to drop the pipes off the side.
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~2.5 miles of tether might be an obstacle.
That's how you bring several kW of power down to an ROV. An umbilical cable, copper conductors and fiber optics inside steel wire sheath. The weight of the thing makes it impossible to attach it directly to the ROV - It would be unmaneuverable - so instead they bring it down to a TMS (Tether Management System) - basically a cage where the steel umbilical terminates and a spool of lightweight tether cable, 100m or so,…
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.
Seems like a pretty stupid design if you ask me
Was it only crew on the submersible or were there paying guests as well?
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It seems like the epoxy in this composite structure is sustaining all of the compressive loads. The carbon fiber would seem to be just along for the ride, so to speak, since fibers are only useful in tension. Am I missing something?
Wouldn't this be a bit like reinforced concrete? In practice there are not just pure compressive loads, but flexing and shearing that put some areas under tension, so the embedded reinforcements fight that and help keep the bulk material in the right places. Also, think of the bill of a toucan or fiberglass surf board. A lot of rigidity comes from the tensile strength of the skin wrapped around an enclosed volume of…
In a negative pressure vessel that's a cylindrical shell, all of the force is being applied uniformly inward from the outside surface of the cylinder, so every part of every fiber will be in compression. There's no part of the structure that outside pressure would deform in a direction that would stretch the fibers -- you would need to have greater pressure on the inside for that to happen, and in that case, the fibers would again all be in tension.
One failure mode to consider is shear failure (i.e. if the changes in circumference due to compression on the outside vs. the inside of the hull are too different, resin between layers could start to fail.
The other would be micro-buckling of tiny sections of fiber in areas where the resin has already failed, or isn't as strong, or in layup defects.
If either of these cause enough deviation from the nominal structure shape to allow buckling to start, the hull will fail catastrophically.
> Also, think of the bill of a toucan or fiberglass surf board. A lot of rigidity comes from the tensile strength of the skin wrapped around an enclosed volume of relatively weak stuff that mostly keeps the skin in the right configuration.
It is like this, but as another comment [1] pointed out, in the case of a negative pressure vessel, the configuration is unstable -- If you develop just one defect, the entire thing implodes. You might be able to buy yourself a little more headroom with something like pre-stressed / post-tensioned concrete (not sure if there's a practical equivalent for carbon composites), but this is a pretty extreme negative pressure vessel...
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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]
What's the matter with that?
It should not have a low-cost consumer-grade controller.
The CEO should not be bragging about the fact that it does, on camera. It demonstrates an incredible lack of experience and/or mental disconnect. All of this would be fine if it were a boat in an amusement park 1 meter pond or something, but it is in the open ocean at depth. It was a matter of time before people died.
Why do they keep emphasizing the fact that the submarine has gone missing and not the people within it?
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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…
Indeed. Which is why space is easier than the deep ocean, a fact that whoever was on that sub may not have fully appreciated.