h a l f b a k e r yYeah, I wish it made more sense too.
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subglider
An up and down human powered gliding submarine | |
We have this killer whale like titanium hull, with flippers and all. In front, a ... is "watershield" the word for it? to see through. Pilot, or captain, or engine, or wathever, is seated inside on a recumbent position. Under the pilot/engine there's a cylinder, inside the faired body, some 20" diameter
by 6 feet long, with a water tight piston. One side of the piston is in comunication with the water, the other with an oil tank via a pedal actuated hydraulic pump. Pump, cylinder and hull can take more than 150 bar of pressure. Flotation is some 500 pounds when the piston is completely "out", -500 pounds when it's "in". You get inside and close the hatch (don't forget!)
then move the piston in, taking water and going down
on a glide, same as a plane does in the air. Ratio could be
about 1 to ten with a very good streamlining, at some
3-4 mph. Could go faster at a steeper dive. When you're gettin to the half mile down and have covered some five miles in horizontal, it's pedal time, pumping oil like crazy untill you displace the piston completely out. Now you glide upwards and have another five horizontal miles.
Again, again and again untill you run out of ocean. Attention that the energy needed to displace the piston at that pressure is no dilly, but can be done.
Why not use a propeller?. Well, it's simpler and less noisy.
Also it pleases me to do so.
Jellyfish swimming suit had more appeal, though.
Human Powered Submarine
http://www.ieee.org...ll03/canadians.html
World record for speed: 8 mph. [Worldgineer, Oct 05 2004]
Gliding Submarines
http://www.stanleysubmarines.com/
.. site about subs that glide without power using bouyancy control .. [bpilot, Oct 05 2004]
Well, it's baked now...
http://news.bbc.co....hnology/7234544.stm
Uses phase change in wax to drive oil in bouyancy tanks. [lurch, Feb 09 2008]
The Slocums
http://www.webbrese..._slocum_mission.htm
Dr. Henry Stommel writes about an autonomous sub glider in this 1989 sci-fi article. Doug Webb conceived the idea based on a variable-bouyancy profiling bouy in the late 1970's. [lurch, Feb 11 2008]
That yellow sub is about as green as you can get.
http://www.whoi.edu...82&cid=37008&ct=162
Woods Hole Oceanographic Institute is using them for thermal, chemical, dynamic, bio, and acoustic surveys. [lurch, Feb 11 2008]
[link]
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Anyone want to figure out how hard that water would be to move? |
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specific weight of water: 62.4 lb/ft^3 = .03611 lb/in^3
1/2 mile = 31680 inches
pressure at 1/2 mile = 31680 * .03611 = 1144 psi
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500 lb of water takes up 8.013 ft^3 or 1154 in^3 of space. To pump out 500 lb of water, you'll need to press against 1144 psi for a distance of 96.2 feet assuming the area you're pushing against is a square inch. |
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Bringing it down to something more reasonable, say lifting a 50 pound weight a foot in the air. You'll need to lift that 50 pounds 2220 times. And I haven't even accounted for friction. |
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//is this much change necessary?// I wouldn't think so, except for reasons of speed. I did my part, who's going to calculate the velocity vs. weight correlation? |
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Worldgineer, that's not 500 but 1000 pounds of water, but do not count the weight at all. The energy is equal to volume by pressure (the same as with the compressed air cars, remember?). In metric units(sorry, I'm a poor Spaniard and do not hablo inglés)
under 1 km water that's 100 bars pressure or 100 kg/cm2 by a volume of 500000 cm3, that's 5 by ten to the seventh power kg x cm, or 5 by ten to the fifth power kg x m. A trained cyclist can do some 25 kg x m
each second easy. The piston has moved all the way in some five hours. Hard, but can be done.
And pack some colaand sandwiches, too. |
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We're coming out with similar answers, though I do agree with your 1000 lb <side note>and I thought the US inch-pound system was silly - I'm hearing pounds, miles, km, bars, and cm from you.</side note>. The problem is, will you have 5 hours to do this pumping? I think you'll need to complete the velocity vs. weight calculation for us. |
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mmmm.... colaand sandwiches. |
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About the speed, you factor the 1/10 glide ratio producing 50 pounds push, and for drag the frontal area, penetration coefficient, profile drag at that Reynolds number, then you forget everything (too complicated) and remember that a good pedal boat makes some 3-4 MPH with a similar push.
Andlooking at the fishies all the time, too. |
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Well that makes no sense - the two use completely different propulsion systems and have completely different drag forces acting on them. Plus, if you make 3-4 MPH you won't have enough time to pump water out. |
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Hey, five hours pumping uses a lot of air. It's also boring. Why not dive less deep and more often?.
One can take in fresh air each time. Also, what happens if te area isn't 1 km deep?. Fancy getting stuck in the mud at the bottom?. A safety counterwheigt will be a good idea. |
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Push is push, if it cames from a propeller or gravity (ask any glider pilot). Anyway, the only way to know the speed with some degree of accuracy short of the real thing is testing a model.
What is the relation pumping time/speed you propose?. I imagine you can pump at rest, even.
I do believe I'll put toghether a model. There are some crazies that race pedal powered subs, you know?. |
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//Push is push, if it cames from a propeller or gravity (ask any glider pilot). // We're not talking about whether there will be propulsion, but how fast it will get you moving. Ask any fighter pilot. |
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Okay, everybody, did a model, doesn't work, too much drag.
What a bummer. |
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Ok, now I'm curious. Computational Fluid Dynamics? Balsa wood, rock, and rubber band? Full scale working model? |
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Well someone has to compress the air. Though I like that as a safety feature - it can be set up to only allow you to dive (take in water) once the air tank has enough pressure to return you to the top. |
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Worldgineer, a pedal boat propeller has a push of about that (50 pounds) and don't think they are marvels of streamlining. Yet they move.
Look at this beautiful model submarine, a sublike ballpen and bits of a prized plane model, plus some BB lead shot, put toghether with super glue, gliding through the inimical waters of my king sized bathtub. It glides, but closer to 1/1 than to 10/1. Well, I know it isn't very refined, but sure trows a bucket of cold water on you. Added the plane model propeller with a rubber band motor and it worked, only the propeller being too big the ballpen...ups!, the hull turned around its axis, too.
I though that yu could regulate your flotation very well this way and let it float, kinda ingravid, mid water. Then, propel it with your standard pedal powered propeller. Using compressed air has several drawbacks, if stored into a tank it would have to be of reasonable size and you could only refill at the surface. And could use it only once !!. Also, you'll have ports under your ballast tank to let the water out, but it will not work if you are upside down. Your regular missile boat doesn't goes upside down very often, but you could, to see that BIG whale in the surface, say.
Budda_pest, I think I have answered you already.
Also, compressed air has this bad habit of expandindg explosively and the energy losses of storing all that energy are greater using air than oil. On the other hand, you can breathe air, but oil only produces diarrhea. So I'll keep the oil for buoyancy adjustement,
and a compressed air tank for safety (to breathe and
blow the tanks if the pump goes stuck).
It's being nicely redesigned, this. Perhaps we should
make one. Who'll be the test pilot?. |
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Marvels of streamlining or not, the bottoms of pedalboats are smooth. The most significant source of drag on your sub will be related to surface area, which is much greater for a sub than a boat. Besides, you're talking about propeller propulsion vs. something else completely. |
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I've not read the book, but a gliding submarine was thunk-up & half-baked by Scott Carpenter in "The Steel Albatross" (yeah, that's the Mercury astronaut Carpenter) |
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Cannonfodder, you forgot the "Aaaw shiiit"
factor : when you are half a mile down and diving
fast, your pedalling power increases exponentially.
Perhaps Buddha_pest pressurized air safety tank, eh?.
Worldgineer, sub hulls have less drag when submerged. Drag area on a hull will depend on total weight and hull elongation. And push is push is push, either propeller, oars, fins or gravity.
Lurch, many thanks for the book tip. I'll look for it, must be interesting. When I was much younger, I used to fly to the Moon with Carpenter, too. But we don't anymore, Moon attractions being lesser than Earth ones. (I did a pun! I did it!) |
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And if I grease the hull with whale oil to make it slippery? |
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Rats! Damnation! Buddha_pest, I just visited the page you suggested ("fuelles flight"). They speak about an up and down subglider. So this is not new.
"Nothing novum sub sole" as my aunt said. But, attention,they are grossly wrong. They pretend not only glide through air (or water) but to generate energy too. !Better than perpetual motion! . Well, you start from a zero energy state (surface) and stop at the same energy level, so where do you get the energy to overcome the drag and move?. Well, in my case, that's exactly the energy that you use to displace the piston.
Which, as we saw, is not trivial.
Ah, thermodynamic laws, everybody abuses them but there they stand !.
Now I will see Worldgineer site about man powered subs. 8 mph is a lot.
I don't believe a sub glider is practical, after my model experience. I desire the best success to the fuelles flight people but don't share their optimism.
Another idea is a very well buoyancy-adjusted sub, with a pedal prop. Could be very nice. Same as a
regular scuba, but dry.
This is a lot of fun. Never enjoyed myself so much discusing concepts. Woulda have know before about hf. |
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Worldgineer, sorry for the inches and metric mixings, I can't handle very well inches and so, I'm metric, so I did a valliant effort to use inches but had to let go when getting to serious calculations.
I'm surprised everybody seems to understand what I write, I'm not supossed to be able to.
Después de todo, pues soy de Sevilla. |
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I believe solar power was used in [bp]'s link. |
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Hello Worldgineer. Just took a look again at your initial calculations and now I understand. Very cleverly done and intuitive. Only I'm such a squarehead I didn´t get it the first time. As you said, we get to the same answers.
I'm working on a bigger model, a fiberglass lifting hull some 0´4 m long, flattened oval section, without front
fins, only directionnal ones. Very clean. Will test this weekend on a swimming pool. To get a medium l/d ratio at more than a crawl, we need a very clean hull
and heavy negative buoyancy.
The man at bp's link is missing a cylinder or has the sparks fouled. He pretends to generate more power
dragging a wind turbine than it's needed to do the dragging. Something about some...what was it...
thermodynamic law, that was. Super-dooper perpetual motion machine, not only moves itsel forever but also produces energy to drag freight trains. If we were ever so lucky, no energy problems anymore. But he sure draws beautiful planes, with folding wings, same as Tomcats. Only Tomcats use them for supersonic flight and such a change of pressure center in subsonic flight will cause a SCREAMING DIVE.
Well, that is neither here nor there.
I'll keep you posted on tests of the model. Bye and take care. |
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Model tested, everybody agreed it made a beautiful sinker, this will be hard to bake but since it's already halbaked I'll abandon it now.
Ah!. It's very sensitive to center of buoyancy location so a single piston arrangement will not work, something with two pistons moving in tandem perhaps. |
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Finflazo, being quite mad, works out the bugs at the halfbakery, and pushes his sleek titanium tube into the deep ocean, pedaling furiously, never to be seen again. |
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...To the strains of "wassermusic".... |
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AH,AH,AH !! I SHALL RETURN !! AH,AH,AH !! (Maniacal, high pitched laugh). |
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See link for info about Karl Stanley and
his unpowered gliding subs. |
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(bpilot) Thanks for the interesting link. I've done some halfhearted efforts, like a fiberglass model, but
I reckon it's nothing like a glider on air; speeds and glide ratio are quite low. |
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I'd rather sail with the wind. |
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A impractical as it is, considering ocean currents and the very slow foraward advance associated with a maximum amount of verticle movement considered practical, I doubt it would be a better means of submersible travel/propulsion than is already in wide use. I unserstand, submarine commanders did this as a means of silent escape from enemy persuers in the last two world wars. |
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Only a brief glance here, but why are we moving such huge volumes of water? Make this baby neutrally buoyant and you don't need to move much at all. And everything you do move goes into vertical speed. We're conveniently neglecting hull compression here, which would really mess with your cylinder seals - you might need a diaphragm instead. |
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And is my brain bad, or can you move a neutrally buoyant object up/down the water column all day with essentially zero energy usage? Ie the only energy expended is via hull friction. Am I right? |
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Are you forgetting the pressure of the column of liquid above you? A neutrally buoyant object is neutrally buoyant only at a certain depth - rising and falling costs energy, because the liquid above or below has a different density. (The Galileo thermometer operates on this principle, right?) |
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Pedantry (sorry, [jutta]): Water density varies very little as a function of depth and increasing pressure, as it's incompressible. What does vary with depth is temperature, and water density usually increases as temperature reduces. The denser water sinks, so temperatures generally get even lower with depth. |
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So, yes, a layer of cold water can stop a nearly neutrally-buoyant RIGID vessel from sinking any further. |
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But in most cases a sinking object that is not rigid will get compressed as it descends, displace less water, and sink faster. A rising object will rise faster and faster as it expands (slowed by friction, of course). Preventing rising or falling TAKES energy, as equilibrium must be maintained. |
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Once something starts up or down, it has the potential energy of the weight difference between it and the displaced water, with friction losses out the wazoo. But rising or falling gives off energy, just like anywhere else. |
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The Galileo thermometer balls are rigid, but they still go from all the way up to all the way down, or back, completely. They just move slow, as there is little force on them. They drop when the water heats up and gets too un-dense to support them. |
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(I think I had a point here, once.) A lot of folks think that ships sink only so far, then stop. Such is not the case, but it's a common belief. If that's not the muddle here, I apologize (and should go to bed). |
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The glider sub in that "yellow" link manages to use the increasing cold to increase its volume and to go back up. |
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150 bar is less than the pressure of a SCUBA tank, so you could power the whole sub using it. The air is used to push the cylinder wherever you want it and then bled back out into the sub so you can breathe it when you move the cylinder the other way. The air coming from the tank would also need to power a pump that forces CO2 laiden air out. The sub would get slightly lighter as you carry less air but this can easily be compensated for using the cylinder. |
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Edit: the system would be much safer if the cylinder was spring loaded so you have to force it in to make the sub go down and just release it to go up. |
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Edit 2: Actually, that would be hard to do, so instead there should be an emergency spring which is loaded before diving and only used on the final ascent. |
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I would want my effort to be in forcing a dive glide rather than an ascent glide .
Could the effort go into shape (therefore displacement) modification ? A concertina glider . |
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Baked in reverse => bad science --- either way MFD |
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