September 13, 2016
Since I brought up “Seaquest DSV” yesterday, I have been thinking about the ridiculous depths to which that boat would dive. Something on the order of 10,000 ft (roughly 2 miles down). Every 33 feet of depth is another “atmosphere” of pressure, so at 10,000 ft, the water pressure is about 303 times that at the surface of the ocean. Roughly two tons per square inch. Powerful.
Humankind’s best submersibles can reach the depth of 10,000 ft. However, the “Seaquest” vessel is much bigger. Bigger means more surface area. More surface area means more square inches. More square inches means more pressure, and more pressure can spell disaster if there is any kind of weakness.
So I got to wondering how such pressures might be handled. The most obvious solution would be the introduction of porous multi-layer skins, where each layer is separated by cells containing water at pressure. Higher pressure cells would be toward the outer layer, with reduced pressure cells further in the skin. That way, compression strength of material can be leveraged with lateral water pressure to allow a thick skin to handle significant pressure variation. It would be absolutely essential that the skin have some sort of natural, automatic way of keeping the pressure higher at the outer skin layers, and also to relieve pressure as the vessel rises. I figure it will be easy enough to take on more water pressure as the vessel dives, so lowering pressure during rises would be the trickier component.
The layout of the cells is also vital to the success of such a skin. If any material has a solid line from the outer surface to the inner surface, the pressure outside the skin will be transferred all the way to the inner skin, resulting in a breach as the pressure rises.
The red lines show where the pressure can follow the material all the way from the higher pressure skin surface (dark blue) to the lower pressure skin surface (light blue) without reducing the pressure per area level. This is a recipe for structural failure.
However, if on the other hand, the cells are laid out so that subsequent layers from the outer skin to the inner skin are offset, then pressures and material flex should spread the pressure out across wider surface areas, due to the varying water pressures in different layers of the skin. There would be no direct material line from the outer surface down to the inner surface. Therefore, the pressure gradient would remain smooth, reducing the chance of a catastrophic collapse.
There is probably more advanced pattern layouts that would allow the skin to absorb pressures without buckling, but this cell layout gives the general idea of the principle.