Last time my blog was diverted from its primary subject was after the earthquake in Haiti, when they couldn’t get food to the people who needed it. Now we are helpless as thousands of barrels of oil are released daily into the Gulf of Mexico. Apparently engineers are working on a “dome-like structure” to cover the leak, but it will take weeks to have it in place, according to BP. Dan the Blogger is NOT happy.
Structures and devices of all sorts can be broken down functionally into tension parts, compression parts, shear-strength parts, membrane parts, etc, Many highly useful things come out of designs that separate and maximize these functions though their geometry. Consider strength to weight ratio of a bicycle wheel. Or a simple bag, as opposed to a box. A tent, as opposed to a house. A balloon. An Umbrella. A suspension bridge. None start with the proposition of taking a pile of building materials and making a solution, although that is the human tendency. Welders think steel, masons think rock or brick, and carpenters think wood. The petroleum business is full of people who make tanks and pipes and valves and scaffolding. So they are welding together a solution.
In this case the remedy would seem to require establishment of a membrane separating the area directly around the source of the oil and the sea at large. This membrane would need to extend a mile from the ocean floor to the surface. This membrane would need to enclose the spill on all sides. The structure can therefore be regarded as a tube.
It is unreasonable to consider spanning the mile to the sea bottom with a solid, unyielding structure, like giant walls or something similar. We are by definition talking primarily tension. More specifically, tension between an anchoring means and floatation means.
Luckily, membrane material in very long lengths is easily available in the form of fabric, and that fabric can be folded upon itself to form a tube. With plenty of overlap, there are many glues of sufficient strength to make sewing unnecessary for open weave fabrics.
Tension members are readily available as cable or rope. Logically, then, the solution would seem to comprise the establishment of seafloor to surface cables and the attachment of fabric to it. It would also seem obvious that a cable running through any chute or tube would alleviate most destructive forces acting upon it, such as being stretched by ocean currents.
All this, to me, leads to an inevitable design conclusion. A tent is constructed with a chimney-like chute, with a cable running through it. The tent is tethered to the ocean floor, and the top of the chute is held up by floatation, first by buoys, and later, perhaps, by the comparatively light weight of the oil inside. No, it’s not as strong or permanent as steel, but it sure would be faster to deploy.
I’ll get back to PRT soon…