h a l f b a k e r yContrary to popular belief
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Ooh... new military vehicle in t minus... |
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"Sir, there's a sandstorm blowing in from the south..." |
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"From the south? But the wind is westerly... give me
the goggles! Echo base, we have a sandworm
bogey, no, make that several sandworm bogeys
approaching our left flank, advise for engagement..." |
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This is interesting enough that I'm surprised it hasn't
been tried. But I can't for the life of me place
anything. Field of deployment is limited but would
seem of some use. |
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It hasn't been tried before because I'm the first guy who thought up the internally ballasted Archimedes screw drive vehicle and so nobody but me has been playing around with them their heads. |
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This is just the latest adaptation to pop into my head. They can travel on land, under-land, under-water, tunnelling through ice of polar moons, even flying as zeppelins. |
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Interesting, localised fluidisation of the sand. I wonder how
far "ahead" you would need to fluidise (to get any useful
forward speed)? A working scale model should be relatively
easy to build (small battery-powered hand-held air
compressors exist, as a starting point). |
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Oh I can't wait until I finish my little mad scientist laboratory. |
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The fun I'm going to have is...
...yet to be imaginable. |
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So many true stories...
... so little time. |
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should be called subsand shirley |
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I've been thinking about the mechanics involved here, and
I'm not optimistic that it would work. See Mark Rober's
excellent YouTube video on how he turned
a hot tub into a fluidized sand play bed. |
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The biggest issue is that you're not in water, you're in
fluidized sand, which won't support the weight of the
vehicle without some very large air buoyancy balloons.
Fluidized sand has a steep phase change curve; there's very
little transition phase between quite fluid that doesn't want
to support any real weight and totally solid. And unlike
water,
there's no substantial density gradient between shallow and
deep to take advantage of, and so there's no buoyancy to
be gained other than that which would be experienced by
any standard-issue helium balloon. It'll just continue to
sink until you shut it off, and then it's stuck 10
meters deep in sand. |
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You're going to need some substantial air pressure, which
means a fan probably on the order of a hundred kilowatts
or more, which means a big diesel engine or some seriously
behemoth batteries. The air pressure and whatever
buoyancy you can manage into the fluidized
sand below must support not just the weight of the vehicle
but also the weight of the sand and air above. |
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That big-ass fan needs a big-ass air inlet that's it's size, so
that becomes a big-ass problem. Your fresh air inlet source
needs
to be on the order of several square feet of surface area or
the fan simply won't breathe. I work with fans such as
these in my job. |
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Maybe what it wants to do is crawl on a solid-ish bed of
sand below it and fluidize the sand in front and above it
somehow. That seems more workable if you can figure out
where the fan intake is. |
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[RayfordSteele] Did you not watch the Mark Rober video
you posted? At timestamp 8:20 there is a nice
demonstration of buoyancy. The kid is floating on his back
much higher than he would in water, which makes sense
because sand is much denser than water. |
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You are quite right about the difficulty in pumping the air.
I think you're going to need more than a fan though since
you'll need really high pressure. I didn't rewatch the whole
video, but I think I remember that Mark Roper used tanks
of compressed air. I'd say the sandmarine would want to
do something similar: run for 30 seconds, then put up the
periscope and run a compressor for 5 minutes to recharge. |
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Maybe a better use model would be a vehicle that moves o
n the surface most of the time, but can turn on the air to
bury or unbury itself to hide. |
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If a surface vehicle drove over this while the air was on, it
would sink half-way in the sand and become permanently
stuck... |
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Re ray's sand link: Whoa!! |
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I did of course watch it. At 8:20 it looks like the video
is sped up and the air is turned way down on his side
of the tub. |
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I like scad's variation as more practical and
workable. Burying a tank in sand this way seems
easy, as long as you
can add the equipment integration in with the armor
somehow, probably an add-on driven by an on-board
compressor. Getting it unburied could be more of a
trick. I might throw this around work to see what
responses I get. |
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Injected? Around itself? Are you sure that's the word you
meant to use? |
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I foresee a time when the sand aspect will be encapsulated within climate controlled tubes to allow submerged passage of goods within tunnels which can not collapse because they are already filled. |
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No storms. No piracy. Guaranteed delivery times. Minimal crews. |
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We have a desert close by, I know I've mentioned this before but, within a four hour drive from my current location exists every climate on Earth.
Desert, rain forest, mountains, lakes, plains, and even giant sequoias. |
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I'm toying with seeing if I can propel a small sailboat on our nearby desert.
If I can get it to gain enough speed then the chance exists that we can use hydrofoils to lift the sailboat and race across our deserts the way we race across water. |
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...and personally I would like to see if I could build a suit which would allow me to sink into and swim through sand... maybe with propulsion. |
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S.C.U.S.A.
A self contained under sand breathing apparatus |
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Why yes, yes I am quite trapped within my own head. |
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As long as your own head doesn't get trapped with-in the sand,
you'll be fine (well, to your definition of "fine"...). |
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// If I can get it to gain enough speed then the chance
exists that we can use hydrofoils to lift the sailboat and
race across our deserts the way we race across water. // |
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While I like the concept, I'm afraid you're missing the
inefficiencies. It's going to take a LOT of energy to fluidize
the sand, and if you're moving fast, you'll need to be
fluidizing a lot of sand very rapidly. |
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Also, I don't think this will be particularly low friction. I'm
guessing the friction will a bit worse than water (based on
the video), but that at higher speeds, the air gaps will
collapse and particles will rub and/or lock together, making
this a non-newtonian fluid. |
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Be sure to make your parts extremely wear resistant and
replaceable. They will be well sandblasted after a short
journey. Note that |
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Note that Mark Roper says in the linked build instructions
to use sand that is as fine and dry as possible. Hopefully
the sand in your local dessert is good enough. I'm assuming
the beach is not going to work since even in the dunes,
the sand is pretty moist a few inches down. Hey
[doctorremulac3], you got space in your car to take an air
compressor with you to the beach on you upcoming
sandbag trip? |
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Could you fluidise the sand with explosives? Det-cord? |
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[pocmloc]; I would say "briefly"...
//..hydrofoils to lift the sailboat...//
I suspect, by the time you take into account the power &
airflow requirements, you might as well have a hovercraft. |
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Right, so, regular and frequent explosions. |
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I think a biomimetic version of the graboids from the Tremors movies should be developed, as they have clearly figured out how to do this already. |
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//While I like the concept, I'm afraid you're missing the inefficiencies. It's going to take a LOT of energy to fluidize the sand, and if you're moving fast, you'll need to be fluidizing a lot of sand very rapidly.// |
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I've thought about this. You'll need "needles" injecting compressed air forward of the craft as well as around. This will not only pre-fluidize the sand about to be travelled through, it will also provide tactile "feelers" to instantly halt forward progress given a large object in the way. |
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I'm more concerned with seeing what might be coming. |
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Ground penetrating radar maybe? |
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// Also, I don't think this will be particularly low friction. I'm guessing the friction will a bit worse than water (based on the video), but that at higher speeds, the air gaps will collapse and particles will rub and/or lock together, making this a non-newtonian fluid.// |
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So we don't move so fast at first. |
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We just make it work... and then worry about fast. We're only going to be able to go so fast before sudden stops will slosh our brains within their buckets anyway. There's a speed limit until it switches to fully automated. |
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"Subarenals", or maybe "hypoconics". |
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I can't help with the physics, but I can provide a veneer of
etymological credibility. |
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[pertinax]; if you sound like you know what you're talking
about, people will assume you do! |
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