4 ms·

Curious how large a floating structure must be to defeat wave motion that threatens to pull it apart.

by aliqot 4y ago

jacquesm 4y ago
It would have to be stupendously large if you ever want to build inside it using ordinary building materials, otherwise it will be like living on a permanent earthquake.
- carapace 4y ago
  Yeah, I wouldn't try to hold back the ocean, I mean more like a floating island the size of Texas or so. But really fractal/crinkly, so there's lots and lots of coastline on the "interior" of the island. The outer edge would buffer storms and high seas. I have no actual idea if this is possible or not. (IANAEngineer or anything like that, just a weirdo on the Internet.) You start with the Great Pacific Garbage Patch. That's a lot of carbon floating on hydrogen and oxygen and salt. You collect the salt, melt it, use that to oxidize the GPGP trash. (Molten Salt Oxidation[1]). Plastic is converted to synthesis gas ("a mixture of hydrogen and carbon monoxide"[2]). Exothermic reaction. Now you need a way to convert the syngas to struts and glue. (I have some ideas on that but they're even nuttier... In any event, syngas is pretty useful stuff.) Use the struts and glue to make large structures out of "octet" truss (space-filling tessellation of octahedrons and tetrahedrons) and just float on top of the water. Imagine an upside-down Frisbee shape with walls roughly 100m tall and a diameter of two or three kilometers. That would be a small prototype. Really the main motive would be to perform a kind of stunt just to get people to realize that we can build very large structures now. [1] https://en.wikipedia.org/wiki/Molten_salt_oxidation https://en.wikipedia.org/wiki/Molten_salt_oxidation [2] https://en.wikipedia.org/wiki/Syngas https://en.wikipedia.org/wiki/Syngas
  - jacquesm 4y ago
    I think you'd be better off building something like that above the ocean with the whole thing supported by piers anchored very deep. Otherwise sooner or later your structure will meet that one wave that it can't deal with and then it's game over. But even something supported by piers would be an amazing feat of engineering by our current standards, even a typical drilling platform that is embedded in the continental shelf is - up close - something to behold. What you are talking about is many, many orders of magnitude more complex, both from a materials science perspective as well as the engineering itself. The sea is a formidable enemy for anything that you intended to float on top of it, in the longer term if you don't sidestep the problem you'll end up with your structure as a submersible. One of the problems is that moving water is incredibly destructive, I've seen 8 cubic meter concrete blocks thrown about like confetti during a bad storm at the coast, and that's nothing compared to what you have to deal with on the open ocean. Have a look at that first image: https://www.alipobiolog.nl/wplog/natuur/na-de-storm-2/ https://www.alipobiolog.nl/wplog/natuur/na-de-storm-2/ That's what left after the impact of a 2x2x2 meter concrete block. These are used to reinforce the piers near IJmuiden, where I used to live and the force of the impact of the water will dislodge those blocks from the asphalt in which they are embedded and throw them over or onto the pier itself. That's approximately 15 tonnes and I have no idea how much force it would require to break them free from their surroundings. Then there is the problem of anchoring your structure. All of the air on the Western side of a floating structure would impinge on the height that the whole thing extends above the sea, turning it into a gigantic sail. Before long your structure would start to move and the mass may work against moving in the beginning, but once it picks up speed the whole thing turns into a giant moving obstacle, eventually crashing into the shore somewhere. If you don't want that you'll have to expend a fair bit of power or anchor it to the seabed somehow, and to withstand such force will require a lot of engineering. This will need to be maintained as well to offset it coming loose in places. On the whole I think the easiest way would be to take an ocean liner and stick it somewhere at an anchor but even that isn't going to be very pleasant without forward motion to counteract a storm (you want to be heading into a storm under power, not float around in it).
    - carapace 4y ago
      > I think you'd be better off building something like that above the ocean with the whole thing supported by piers anchored very deep. That's the idea, but instead of piers you have a grid of floats or buoys. The octet truss structure is light enough and strong enough to float on just the tops of the waves. > Otherwise sooner or later your structure will meet that one wave that it can't deal with and then it's game over. The largest wave so far recorded (not counting tsunami) was an 84-foot (25.6m) rogue wave off Norway. I figure you would need some sort of dissipative structure rather than a flat wall. Something akin to Tesla's valvular conduit with flexible baffles and fins to turn the water's kinetic energy back onto itself. Probably 300m thick or more so you have plenty of room/time in which to work. > What you are talking about is many, many orders of magnitude more complex, both from a materials science perspective as well as the engineering itself. Oh, I hope not! The structure is conceptually simple, at least, and the materials should be mostly off-the-shelf. I have no real idea, of course. > The sea is a formidable enemy for anything that you intended to float on top of it Oh, yes. I've lived next to the ocean for the vast bulk of my life so far. Although I'm not nautical, I can't imagine living far from it for long. Our Pacific ocean here is much sweeter and kinder than your stern North Sea, of course ("pacific" eh?) But it is still a god. I don not worship the ocean but my respect for it falls not far short. When I watch video footage of big storms out on the deep water I think I'm crazy, but then I think about just how big of a structure I could make, and I'm enthused again. > Then there is the problem of anchoring your structure. All of the air on the Western side of a floating structure would impinge on the height that the whole thing extends above the sea, turning it into a gigantic sail. That is easy, in theory: windmills instead of sails, driving propellers to keep on station. - - - - I'm more or less going to actually try this. The initial prototype will be very small, probably around 200m in diameter, and it will look more like a spider or water-strider bug than a platform.

Curious how large a floating structure must be to defeat wave motion that threatens to pull it apart.

by aliqot 4y ago

Curious how large a floating structure must be to defeat wave motion that threatens to pull it apart.

It would have to be stupendously large if you ever want to build inside it using ordinary building materials, otherwise it will be like living on a permanent earthquake.

carapace 4y ago
Yeah, I wouldn't try to hold back the ocean, I mean more like a floating island the size of Texas or so. But really fractal/crinkly, so there's lots and lots of coastline on the "interior" of the island. The outer edge would buffer storms and high seas. I have no actual idea if this is possible or not. (IANAEngineer or anything like that, just a weirdo on the Internet.) You start with the Great Pacific Garbage Patch. That's a lot of carbon floating on hydrogen and oxygen and salt. You collect the salt, melt it, use that to oxidize the GPGP trash. (Molten Salt Oxidation[1]). Plastic is converted to synthesis gas ("a mixture of hydrogen and carbon monoxide"[2]). Exothermic reaction. Now you need a way to convert the syngas to struts and glue. (I have some ideas on that but they're even nuttier... In any event, syngas is pretty useful stuff.) Use the struts and glue to make large structures out of "octet" truss (space-filling tessellation of octahedrons and tetrahedrons) and just float on top of the water. Imagine an upside-down Frisbee shape with walls roughly 100m tall and a diameter of two or three kilometers. That would be a small prototype. Really the main motive would be to perform a kind of stunt just to get people to realize that we can build very large structures now. [1] https://en.wikipedia.org/wiki/Molten_salt_oxidation https://en.wikipedia.org/wiki/Molten_salt_oxidation [2] https://en.wikipedia.org/wiki/Syngas https://en.wikipedia.org/wiki/Syngas
- jacquesm 4y ago
  I think you'd be better off building something like that above the ocean with the whole thing supported by piers anchored very deep. Otherwise sooner or later your structure will meet that one wave that it can't deal with and then it's game over. But even something supported by piers would be an amazing feat of engineering by our current standards, even a typical drilling platform that is embedded in the continental shelf is - up close - something to behold. What you are talking about is many, many orders of magnitude more complex, both from a materials science perspective as well as the engineering itself. The sea is a formidable enemy for anything that you intended to float on top of it, in the longer term if you don't sidestep the problem you'll end up with your structure as a submersible. One of the problems is that moving water is incredibly destructive, I've seen 8 cubic meter concrete blocks thrown about like confetti during a bad storm at the coast, and that's nothing compared to what you have to deal with on the open ocean. Have a look at that first image: https://www.alipobiolog.nl/wplog/natuur/na-de-storm-2/ https://www.alipobiolog.nl/wplog/natuur/na-de-storm-2/ That's what left after the impact of a 2x2x2 meter concrete block. These are used to reinforce the piers near IJmuiden, where I used to live and the force of the impact of the water will dislodge those blocks from the asphalt in which they are embedded and throw them over or onto the pier itself. That's approximately 15 tonnes and I have no idea how much force it would require to break them free from their surroundings. Then there is the problem of anchoring your structure. All of the air on the Western side of a floating structure would impinge on the height that the whole thing extends above the sea, turning it into a gigantic sail. Before long your structure would start to move and the mass may work against moving in the beginning, but once it picks up speed the whole thing turns into a giant moving obstacle, eventually crashing into the shore somewhere. If you don't want that you'll have to expend a fair bit of power or anchor it to the seabed somehow, and to withstand such force will require a lot of engineering. This will need to be maintained as well to offset it coming loose in places. On the whole I think the easiest way would be to take an ocean liner and stick it somewhere at an anchor but even that isn't going to be very pleasant without forward motion to counteract a storm (you want to be heading into a storm under power, not float around in it).
  - carapace 4y ago
    > I think you'd be better off building something like that above the ocean with the whole thing supported by piers anchored very deep. That's the idea, but instead of piers you have a grid of floats or buoys. The octet truss structure is light enough and strong enough to float on just the tops of the waves. > Otherwise sooner or later your structure will meet that one wave that it can't deal with and then it's game over. The largest wave so far recorded (not counting tsunami) was an 84-foot (25.6m) rogue wave off Norway. I figure you would need some sort of dissipative structure rather than a flat wall. Something akin to Tesla's valvular conduit with flexible baffles and fins to turn the water's kinetic energy back onto itself. Probably 300m thick or more so you have plenty of room/time in which to work. > What you are talking about is many, many orders of magnitude more complex, both from a materials science perspective as well as the engineering itself. Oh, I hope not! The structure is conceptually simple, at least, and the materials should be mostly off-the-shelf. I have no real idea, of course. > The sea is a formidable enemy for anything that you intended to float on top of it Oh, yes. I've lived next to the ocean for the vast bulk of my life so far. Although I'm not nautical, I can't imagine living far from it for long. Our Pacific ocean here is much sweeter and kinder than your stern North Sea, of course ("pacific" eh?) But it is still a god. I don not worship the ocean but my respect for it falls not far short. When I watch video footage of big storms out on the deep water I think I'm crazy, but then I think about just how big of a structure I could make, and I'm enthused again. > Then there is the problem of anchoring your structure. All of the air on the Western side of a floating structure would impinge on the height that the whole thing extends above the sea, turning it into a gigantic sail. That is easy, in theory: windmills instead of sails, driving propellers to keep on station. - - - - I'm more or less going to actually try this. The initial prototype will be very small, probably around 200m in diameter, and it will look more like a spider or water-strider bug than a platform.