If an internally ballasted Archimedes-screw propelled vehicle had the capability of injecting compressed air around itself, then travelling under dry desert sand would be no more difficult than travelling through water. Up periscope/air intake through the fluidized sand and you're good to go.-- 2 fries shy of a happy meal, Feb 06 2022 Mark Rober https://www.youtube...watch?v=My4RA5I0FKsArguably my favorite YouTuber. [RayfordSteele, Feb 06 2022] Ooh... new military vehicle in t minus...
"Sir, there's a sandstorm blowing in from the south..."
"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..."
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.-- RayfordSteele, Feb 06 2022 The Spice Must Flow!
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.
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.
True story.-- 2 fries shy of a happy meal, Feb 06 2022 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).-- neutrinos_shadow, Feb 06 2022 Exactly.
Oh I can't wait until I finish my little mad scientist laboratory.
The fun I'm going to have is......yet to be imaginable.
So many true stories...... so little time.-- 2 fries shy of a happy meal, Feb 06 2022 should be called subsand shirley-- pocmloc, Feb 06 2022 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.
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.
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.
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.
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.-- RayfordSteele, Feb 06 2022 [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.
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.
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.
If a surface vehicle drove over this while the air was on, it would sink half-way in the sand and become permanently stuck...-- scad mientist, Feb 07 2022 This idea is grit.-- AusCan531, Feb 08 2022 Re ray's sand link: Whoa!!-- doctorremulac3, Feb 08 2022 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.
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.-- RayfordSteele, Feb 08 2022 Injected? Around itself? Are you sure that's the word you meant to use?-- 21 Quest, Feb 08 2022 It's the latest fad.-- 2 fries shy of a happy meal, Feb 08 2022 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.
No storms. No piracy. Guaranteed delivery times. Minimal crews.
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.
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.
...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.
S.C.U.S.A. A self contained under sand breathing apparatus
...
Why yes, yes I am quite trapped within my own head.
Why do you ask?-- 2 fries shy of a happy meal, Feb 08 2022 As long as your own head doesn't get trapped with-in the sand, you'll be fine (well, to your definition of "fine"...).-- neutrinos_shadow, Feb 08 2022 // 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. //
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.
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.
Be sure to make your parts extremely wear resistant and replaceable. They will be well sandblasted after a short journey. Note that
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?-- scad mientist, Feb 08 2022 Could you fluidise the sand with explosives? Det-cord?-- pocmloc, Feb 08 2022 [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.-- neutrinos_shadow, Feb 08 2022 Right, so, regular and frequent explosions.-- pocmloc, Feb 08 2022 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.-- RSMilward, Feb 08 2022 //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.//
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.
I'm more concerned with seeing what might be coming.
Ground penetrating radar maybe?
// 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.//
So we don't move so fast at first.
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.-- 2 fries shy of a happy meal, Feb 09 2022 "Subarenals", or maybe "hypoconics".
I can't help with the physics, but I can provide a veneer of etymological credibility.-- pertinax, Feb 09 2022 [pertinax]; if you sound like you know what you're talking about, people will assume you do!-- neutrinos_shadow, Feb 09 2022 Scary, isn't it?-- pertinax, Feb 09 2022 random, halfbakery