• Acetamide@lemmy.world
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      1 year ago

      I’m 100 percent certain that this is a spacecraft or launcher fuel tank. I’ve worked on reentry analyses of spacecraft fuel tanks before, and I can tell you that these very commonly survive re-entry for several reasons.

      Firstly, they are by far the largest components housed inside the vehicle’s outer structure. The structure usually takes the brunt of the aerodynamic and thermal forces, protecting the tank from the largest destruction.

      Secondly, the tank itself has to handle the huge fuel pressures involved (easily going towards many hundreds of atmosphere pressures!). This obviously means that incredibly tough materials have to be used.

      Thirdly and finally, as can be seen in the pictures, their shape is symmetric, making the shape aerodynamically very unstable. This means the fuel tank has the tendency to tumble in the airstream. The tumbling continuously causes different parts of the tank to be exposed to the heat and other parts to cool down.

      Fuel tanks are the major risk during reentry to people and other stuff on the ground, perhaps together with the massive engine blocks. To minimise the chances of hitting someone or something, re-entries are nearly always aimed at the Pacific Ocean, hence them being more likely to wash ashore in Australia.

    • DogMuffins
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      1 year ago

      better article.

      What’s the fibre pattern on the dome part I wonder? Looks like some kind of carbon fibre maybe around the top in the video.

      I wonder why it was buoyant. Like if it’s just the sheared off end of a cylinder you’d think it would just sink?

      IDK enough about anything to say “I reckon it’s x”, but if it’s not rocket parts then my guess would be some kind of reusable buoyancy tank used for things like floating foundations into place, shipbreaking yards, that sort of stuff.

      • heluecht@pirati.ca
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        1 year ago

        @DogMuffins @Amilo159 Maybe it also has got some insulating foam. This would make it floatable. This really looks like some tank. It looks toasty, so the question is: 1st stage or 2nd stage?

        • Acetamide@lemmy.world
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          1 year ago

          Many “space” fuel tanks have inflatable bladders inside to control the pressure and location of the fuel, especially in zero-g. Otherwise, the fuel could float away from your tank valve. It is possible that this tank has a fully or partially inflated bladder, making it much more buoyient.

      • DontNoodles
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        1 year ago

        Kevlar fibers are also used commonly in rocket/satellite manufacturing.

      • AFK BRB Chocolate@lemmy.world
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        1 year ago

        If it’s an empty or near-empty fuel tank, it’s going to float, whether the inside is a vacuum or pressure is equalized with a gas.

        • DogMuffins
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          1 year ago

          the “object” in the picture is not sealed, or doesn’t appear to be.

          • AFK BRB Chocolate@lemmy.world
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            1 year ago

            Hard to say what’s inside what we can see, but if nothing else the upper visible part must have been intact and enough air still in it to keep it buoyant.

      • FigMcLargeHuge@sh.itjust.works
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        1 year ago

        I wonder why it was buoyant. Like if it’s just the sheared off end of a cylinder you’d think it would just sink?

        Something doesn’t have to be buoyant to wash up on shore.

        • CM400@lemmy.fmhy.ml
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          1 year ago

          I’m the photos one can clearly see a line where part of the object was out of the water, since there’s no barnacles above that line. Also, if one were to read the article linked, one would read

          (Italics mine)

          “Sometime yesterday, a local lady and her partner discovered it just floating on the edge of the water and dragged it out with their four-wheel drive,” he said.

        • DogMuffins
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          1 year ago

          That’s true, however you can see from the barnacles that this object is in fact buoyant.

          • FigMcLargeHuge@sh.itjust.works
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            1 year ago

            I don’t know enough about this to argue, so sure. We are all just jumping to conclusions though. It could have been partially submerged somewhere else, gathered the barnacles, and then relocated to this beach after a storm. Who knows…