h a l f b a k e r yThe embarrassing drunkard uncle of invention.
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Giant glass balls containing nothing are anchored underwater. When a tidal wave passes over them, they collapse, reducing the volume of the wave.
The vacuum spheres resemble Japanese fishing-net floats, but are much bigger. Their density is less than that of sea-water, allowing them to float. The
glass is strong enough to withstand the vacuum inside and water pressure outside, until shattered. The trigger mechanism, which can be networked, senses the pressure of a sufficiently-large wave passing above and fires the shattering device.
The floating spheres are connected to cables that keep them at the proper position and depth in the water. The depth below the surface is a function of the size of the wave considered to be dangerous. The spheres must be close enough to the surface to affect the tsunami, yet deep enough to be below surface traffic. A forest of vacuum balls would interfere with some marine activities, but should be below most small boats. A forest of spheres will attract fish, but will not be compatible with most major fish-harvesting activities. A sphere field should be marked on navigation charts.
The netting around the balls can be made to contain the shattered glass, which should be tempered to produce small, rounded fragments. The collapsing of a sphere may be a similar to an explosion, and can have an affect on nearby organisms. The netting can, in addition, carry stiff flanges arranged to help reduce the tsunami wave's action through the generation of turbulent resistance to the wave's movement, while allowing the inflow of water into the vacuum space.
The anchors for the spheres are concrete castings such as are often used as bouy anchors, and can contain a pressure-sensor package. Close to shore, where there is not sufficient water depth to allow for a floating ball under surface activities, vacuum chambers can be placed within the concrete anchors. Those chambers can be fitted with domed glass lids and trigger mechanisms, and are used in place of the floating balls.
The volume of vacuum balls required to completely collapse a wave will be that which equals the volume of the wave. A lesser volume will reduce the size of the wave. This volume of balls will be spread horizontally along the path of the potential wave.
The cost of manufacturing will not be trivial, but can be set up for mass production. The balls will be blow-molded and tempered, then pumped free of air and sealed. The material for making the glass may be available as sand, locally, or from the sea floor. The delivery and installation of the vacuum balls will be similar to standard buoys, with additional handling problems, and the advantage that materials and products could be transported via ship.
The vacuum balls will probably be deployed off towns and harbor mouths. Costs will probably prohibit protection of large areas. The dynamics of wave travel will have to be considered in the arrangement of vacuum-sphere arrays. The triggering and collapse of a series of vacuum spheres could be considered the equivalent of digging a hole in the water for the wave to fall into. Any amount of spheres deployed will have some effect on the size of a wave.
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If you allowed companies to advertise on them, you could reduce the costs, probably.
How big would these actually be? I like the idea of 40' spheres bobbing around the surface of the sea.
I think that the trigger mechanism would have to be very good, because you would not want the sphere to explode under a very small wave, and likewise you would not want the ball to just float and let the tsunami go past.
The net would have to be quite fine, so as not to allow thousands of pieces of shattered glass to wash up on the shore. The nets would have to be collected later, and the glass recycled.
The anchors would have to be positioned very carefully so as not to harm coral.
Phew. That was a long annotation.
Bun. |
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Newsflash: Terrorists have attacked a popular beach resort, today. Apparently they triggered a huge nest of tsunami spheres using suicide frogmen. |
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Imagine a tsunami with an open-water surge of just 50cm (18 inches), but a wavelength of 150km (almost 100 miles). A 100 metre (yard) wide harbour entrance would require 8300 12 metre diameter spheres to "sink" that amount of water. Still, bun, just to wipe off the evil grin of one of those pesky tsunami. |
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Thanks, [copro] I hadn't had time to do the math--which would have taken me a lot longer than it took you. I know it would take a lot of them. |
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[dbmag9] I didn't think of advertising, as they will be out of sight underwater. But divers might see them, and may want to go diving amongst them--provided nobody pops a sphere, of course. |
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I didn't try to figure size, as the variables are many.
I was just happy to find a use for vacuum spheres. Installing these things will contribute something to the rise of sea levels, BTW. |
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I don't know how much of a factor the forward motion of the water in a tsunami is. This idea assumes that reducing a wave is simply a matter of reducing vertical rise, although the flanges-on-the-netting bit might help slow horizontal motion. |
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If the flanges slow the water from draining out before the wave arrives, that could be bad . . . or maybe not. Computer modelling of drainout preventers, anyone? |
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What I didn't mention [baconbrain] is the 900 tonnes of buoyancy each 12m sphere would have - it is going to take a lot of anchoring, so I suspect they're likely to result in the rise of sea-floor levels too. |
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What [cropocephalous] said, because I'm not smart enough to say it myself. But bun for the very original thought. |
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//The collapsing of a sphere may be a similar to an explosion// |
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Pedant: IMPLOSION not explosion. |
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Though methinks it would work better if the were anchored at the bottom of the ocean, as then they would suck the water down and slow the tsunami more effectively (I think). |
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So if we take [sfb]'s figures, there are about 8 across the width of the 100m harbour entrance(assuming they're touching in a rectangular arrangement), spread out to sea over 12.5 km (over six and a half nautical miles). |
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When I read the title I thought these would be super-strong spheres that people would get in when a tsunami was approaching to protect them. That would be kind of a fun ride at a water park. |
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Fun except for the vacuum bit. Maybe you could pack em full of explosives and blow the wave clean out of the water as it passes. |
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maybe not, just got a visual of a flying tsunami wave. |
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You're talking about a crazy amount of these things to be effective. Instead, why not drill a crazy series of crazy deep holes (same volume as the spheres you'd need), evacuate them, and put a huge hinged lid on each hole (opens down). That way, they're re-usable. Sure, it might take years to re-evacuate them, but you usually have years between tsunamis. And yes, that's a lot of pressure to resist with the lid to the hole, but the sphere is similarly challenged, seems to me. |
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[oxen crossing] that's an interesting variation that had not occurred to me, with some real advantages. The water would be falling downward, limited only by friction against the sides of the boreholes. I think you'd need a casing on the holes, at least the top part, which gets back to something close to my mention of //vacuum chambers can be placed within the concrete anchors//. |
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If I was to drill holes in the sea floor, I'd do it at the place where the sea floor was going to rise during the earthquake. I thought about placing the spheres on the bottom there, but figure it would be almost impossible to predict the location. It would stop the wave at its source, and probably require less volume of vacuum. |
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//Pedant: IMPLOSION not explosion.// True indeed, and well noticed. But still very similar to an explosion, as I learned when I was fixing televisions--never, never drop a picture tube. |
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Which makes for an interesting thought: The skills needed to make tsunami spheres are being lost as TV makers switch to flat screens. |
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An evacuated hole in the seafloor whose cover is opened- The water would hit the bottom SO HARD! Wouldn't this generate the same amount of force, minus inefficiency, as the original earhtquake? |
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I'm not sure, but it seems like there would not be a sudden event where all the force of the initial quake would hit at once (minus drag), as the wavelength is long in the open ocean, and would be absorbed gradually as the wave passed by, if the hole is sized to limit the intrusion of water to a rate that takes the entire wavelength to fill the hole. I assume the holes would be placed in areas to protect particular places on land, not to try to guess where an earthquake might happen. |
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Interesting dynamics. I wonder if you would get any cavitational side-effects by imploding that many spheres. To date they haven't been able to produce the theoretical gigakelvin but they haven't hit it with an oscillator capable of producing that magnitude of wave either. You may end up evaporating your wave or fusing it into a hunk of scrap iron. Certianly an unanticipated result. I would think you may have more benefit from the crazy-hole field suggested by [oxen crossing] but rather than evacuating the cavity to a vaccume, pump the water out, pump in compressed atmospheric gasses and then cap it. You would be able to diffuse some additional wave intensity by disruption by the downflow into the hole and the upward expansion of the escaping gasses. |
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I dunno, if the sphere burst as the tsunami passes over, the water of the wave will be displaced a little, but wouldn't it still have the same forward momentum? I figure it would be more efficient to detonate the sphere after the wave passes, to suck it backwards, thus slowing it down. |
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