If we can *easily construct pressure vessels that can contain pressure far greater than that of the deep sea internally (high pressure inside, low pressure outside), what are the challenges that prevent us from making a vessel that can withstand deep sea pressure externally while maintaining low pressure internally?
In: Engineering
It is simpler to have high pressure on the inside. consider a cylindrical container that is made of a thin metal sheet.
It will stretch out the container and all parts will be in tension all the time. So the long sides are stretched out and you can use the full strength of the material you use
If the low pressure is on the inside the container is compressed. The long walls are now compressed. It is no like if you have a load on a beam, the inside is stretched and the outside is compressed. The amount of force depends on the depth in the walls, there is no pressure in the center of the wall. It can then start to buckle and break apart.
A simpler way to look at is high internal pressure is If you hang something from a wire, it is stretched and all of the material is used. High outer pressure is like if you balance something on a beam, you need a lot more material because as soon as it starts to bend in any direction only part of the beam handles all of the force. You can hang from a lot thinner metal wire than the thickness of a metal beam you can stand on.
The result is the pressure vessel is successful deep sea submersible will be a sphere, which is the shape where it all can get compressed without any bending. The Titan that imploded was a cylinder
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