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A twin tubed snorkel is valved so that one tube is used for inhaling, the other for exhaling.
At the top end is a chamber seperated into two volumes by a central diaghragm.
The two tubes are coupled to the two volumes. The exhaling volume is vented to atmosphere via a pressure limiting valve. The
inhaling volume has a check valve which allows air to enter from atmosphere. The diaphragm is sprung toward the exhaling side.
As air is exhaled under pressure (because the diver is at depth) the diaphragm is pushed and air in the inhaling chamber is compressed. When the chambers reach the preset pressure, remaining exhaled air is vented to atmosphere through the pressure limiting valve.
Since the same volume of air is inhaled as is exhaled and the change of pressure is the same in each case, there is no loss or gain of energy, so the only extra effort required would be due to the ineffeciencies of the system.
A useful addition could be an air pump actuated by pulling on the tubes against the bouyancy of the device. Especially useful in panic situations when the diver uses the tubes and bouyancy to pull him/herself back to the surface.
Twin tube snorkel with valves
http://www.freshpat...ptan20060102176.php
But no cross-chamber pumping action...I don't think that you can get there from here - isn't there something about conservation of energy? [normzone, Apr 13 2010]
baked
http://en.wikipedia.org/wiki/Snuba
Snuba. Saw it in Eilat in 1995. Safety like scuba still needed. [pashute, Mar 22 2011]
Diving suit
http://en.wikipedia.org/wiki/Diving_suit
all you need is a compressor [EdwinBakery, Mar 22 2011]
Artificial gill
http://www.engadget...-oxygen-from-water/
a more recent development [EdwinBakery, Mar 22 2011]
Underwater_20Hullaballoon
[spidermother, Apr 10 2011]
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//not the Jethro Tull album// |
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Unless, *of course*, the snorkel is shaped like a flute. |
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I think you are over estimating the amount of air in a snorkle and/or the amount of flotation that amount of air would create. I think this is a rebaking of the artificial lung vests they created to allow submariners to escape to the surface. I'll have to find a link, maybe it is the aqua-lung mentioned. |
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The one I'm thinking of is the Momsen Lung, but it seems to include some CO2 treatment options. |
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At say 10' depth, exhalation requires no energy, the air is pushed out of the lungs. Twizz's contraption trades off that energy: exhalation requires a positive effort, but that energy is used to alleviate the amount of energy required to suck air in from the surface. |
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" that energy is used to alleviate the amount of energy required " |
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I don't think the two will balance, but maybe a maths specialist will come along and render an opinion. |
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Mr.QED; The bouyancy comes mainly from the pressure chamber, which would need to have a capacity of several litres. Each breath would be about 20% of the chamber volume, so that the pressure change during each cycle would be small enough that the diver does not need to blow or suck hard. |
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Norm; Imagine pushing a 3 litre balloon under water to a depth of 3m. That would require approx. 90 joules of energy. All that energy is stored in the mass of the displaced water and can be recovered as the balloon rises back to the surface (less losses due to friction etc.) |
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Bigsleep; I had a search for similar ideas, but couldn't find any surface supplied system which was independent of some kind of externally powered pump. I'd be interested if such a system already exists. |
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[bigsleep], aqua-lung inventor... someone French, non? |
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The Aqua Lung was invented by Jaques Cousteau. It is a storage based system, with air tanks, not a snorkel. |
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if you can imagine 2 balloons (not rubber ones): one at the surface and one at depth: the energy it would take to pull the one on the surface down is the same as the energy released by the other one rising up. If you instead simply release the "down" balloon it will float happily and quickly to the top then you have a bitch of a time getting the other balloon down to depth. |
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[Bigsleep] You are correct, the regulator uses a diaphragm. |
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In that application, the diaphragm is used as a pressure sensor to control flow from a pressurised tank. |
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In my idea, the diaphragm is used to balance pressure between inhaled and exhaled air without allowing them to mix. |
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Pete, (Twizz) how do I contact you. I have two
simple and interesting bike ideas... my email is my
user at gmail. Moshe. |
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long time baked. Diving suits. All you need is a compressor at the surface pumping air to a tube that goes into the suit, and then the typical regulators and exhale-exhaust and whatever. |
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Used them to do underwater work for a long time and I think they still do |
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a more recent development is a system that pulls dissolved oxygen from water via a centrifuge, creating the potential for much longer-lasting scuba tanks (you'd still eventually run out of energy to run the system). |
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Very cool idea. If I understand the idea correctly, you'd definitely need the active airpump to get the air down below a couple of feet. |
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If this wasn't 100% efficient (which would be silly as that would be perpetual motion), then you'd start with 1 lung full of air, then after one breath, you'd have say 0.9, then 0.81... 0.72... 0.65... 0.6... Before long you either find out this is a quadratic and it starts getting bigger again or it's time to find a new diver. |
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In order for this to work you need the fresh-air tube of a pliable material inside the stale-air tube of rigid material. |
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The respirator bag is of course fed by the fresh tube, and the top flapper valve on the stale tube is pressure limiting to equal or greater than the depth pressure (minus sea level pressure). The rest of the flapper valves, one at each end of each snorkel and an extra one between respirator bag and mouthpiece, are very lightly sprung closed. |
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So, we start the cycle with air in both tubes, respirator bag depleted, and the diver with full lungs. |
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The diver breathes out, compressing the air in the stale tube which in turn compresses the fresh tube which squeezes air into the respirator bag. |
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The diver then breathes in from the respirator bag. |
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Before breathing in again the stale-limiter-valve up top is opened. The stale air flows out, and the fresh tube springs back to its original shape, pulling in fresh air as it does so. |
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For clarification note that there's probably no elegant way of having the limiter valve open automatically between breaths, it would probably be a manual pulling of a string or something and the valve has to be kept open until the stale air escapes and the fresh tube has returned to its normal uncompressed state. |
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[edit]: actually a pressure-limiting valve is unnecessary: it should be a simple cover that slides aside (pressure independent). The point in the cycle where this takes place would be during the inhalation, so something attached to the flapper valve between respirator bag and mouthpiece automatically opens it when the diver breathes in from the respirator bag, and closes it when enough time has elapsed to balance the snorkel. |
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In order to combat any small amount of air loss, a hand bulb could also be incorporated in the tangle somewhere to add a bit of pumping volume during the exhalation stage. |
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Other than that, not only will it work, but the effort would be less than that required to breathe through a regular snorkel at a much shallower depth. |
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[FT] If I understand correctly, yuor proposal is identical to mine, except that you are using the inner tube in place of the diaphragm. |
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My reasons for using the diaphragm were; |
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1) It confines all the 'works' to a self-contained unit. The hoses are simple tubes. |
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2) It provides a convenient floating bouy to support the upper end above water level |
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Ah, right... good point about the diaphragm vs inner-tube, but I'm pretty sure you also need a respirator-bag down where the diver is, ie: fresh-air-tube > respirator-bag > mouthpiece. Or maybe it's just my visualization. When I recall where I left my brain yesterday I'll get back to you |
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What if you dive quickly... Say you start at the surface with one lung full, then go down 10m in a couple of seconds. You'd then only have half a lung full as the pressure is double there. Would take quite some pumping with the hand bulb to get back up to a single lung volume. |
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And then, if you come up quickly, the air has to go somewhere. So either the diaphragm, the hand bulb or you explode! Could be solved with a whoppie cushion type valve though. |
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I'd be impressed if anyone could make 10m depth in 2 seconds. |
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Sure, if you try hard enough you can make it not work. Don't try. |
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Coming up quick enough that gas expansion in the lungs or the device is an issue would be disastrous for the gas dissolved in the blood. AKA the Bends! |
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Snuba uses compressed air stored in tanks on the raft; classical diving suits use a powered compressor at the surface. Both are completely different from this idea, which uses a pressure exchanger to increase the efficiency such that the diver can do the work alone. |
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A large remaining inefficiency in this idea is caused by the changing pressure in the pressure chamber. |
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You might need the pressure vessel to be a non-rigid (or semi-rigid) container at the same level as the diver. As he exhales, fresh air is driven, by movement of the diaphragm (which is at the surface), down into the pressure vessel, inflating it. The pressure in the entire system will thus be automatically regulated to correspond to the hydrostatic pressure at the diver's depth. A further advantage is that the volume of the diver-plus-vessel remains approximately constant, reducing bobbing up and down with each breath. |
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I think this pressure vessel might be where part of [Toaster]'s brain is. |
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(Bother. I can't work out a simple way to reset the diaphragm while recovering the remaining pressure potential in the exhaust air. It must be doable though.) |
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(Later) If the device at the top is a pressure exchanger it all works fine. |
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Give or take a bit of reality tax, it works... |
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The equalization box has an intake side and an exhaust side. Between them is a very loose diaphragm with a displacement at least equal to the diver's lung capacity at depth. The atmosphere intake flapper valve is very loosely held shut. The exhaust-to-atmosphere valve is a sliding window-type. |
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When the diver breathes out, the pressure pushes the diaphragm which pumps air through a one way valve into the breather bag: a bag which is at depth with the diver. Then the exhaust valve is manually opened which allows the exhausted air to escape, which returns the diaphragm to neutral which allows the intake valve to open to refill the intake side. (whew). |
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The diver breathes in from the breather bag. |
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The amount of extra effort involved is mininal: on exhaling the diver has to push a bit to accomodate drag through all the piping, and the return-spring/thing of the exchange diaphragm and intake valve of the breather bag. |
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Also the exhaust-to-atmosphere valve is manually operated (I can't think of any easy mechanical method of doing that). |
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At the end of an exhalation, the exhaust air is still at dive pressure. When the exhaust valve is opened, the exhaust air must expand as it reaches atmospheric pressure (since air is compressible). This represents a large amount of work, which of course the diver must supply in compressing the fresh air. |
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Also, while the volume of fresh air taken in equals that of the exhaust air, the quantity is (much) less, so the system quickly runs out of air. |
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If the expanding exhaust air could transfer its energy to the fresh air which is filling the chamber on the other side of the diaphragm, this problem would be solved. Hence my mention of a pressure exchanger - but it needs to be a rather tricksy one to account for the changing pressures in the two fluids. Pressure exchanger designs mostly seem to assume that the fluids are incompressible, which makes the task much simpler. |
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To put it another way, you're trying to transfer energy from a fluid whose pressure goes from high-to-low, to another fluid whose pressure goes from low-to-high, which is a non-trivial problem. |
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//pressure exchanger// Yes, I've the feeling that the diver can only supply half, but I can't think of why. |
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Picture the surface-dwelling pex as a closed cylinder with a free'ish piston in the middle. "Free'ish" because it's *slightly* sprung to the left. |
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On the left side is the input from the mouthpiece exhaust pipe and the sliding exhaust valve to the atmosphere. On the right side is the intake pipe leading to the breathing bag down where the diver is, and a lightly sprung flapper intake valve that allows air in (but not out) from the atmosphere. |
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So each side has a valve to/from the outside and a pipe to/from dive-depth. |
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The diver breathes out. This pushes the piston to the right which empties the intake manifold (through the intake snorkel) into the breathing bag. The bag expands. |
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The diver operates the pex exhaust-release (a long piece of string or something <wince>). The exhaust air whooshes out and the piston drifts over the to the left, which opens the intake valve and allows fresh air into the intake manifold. |
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The piston makes for an easy picture, but in reality would be more effort to operate than something like a shaped semi-rigid conical diaphragm which can expand the volume difference of the diver's lung capacity. |
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(precious anno edited) (sp. previous - Freudian?) |
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//piston// ... //sprung// Yes, that's exactly how I've represented it in my diagrams. |
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//whooshes// Yes, there's the rub. You worked hard for that whoosh! |
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Again, this problem only arises because air is compressible. |
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//worked hard for that whoosh// Actually I don't think so... mind you I'm a bit out of my depth ;-) on this, but I think the only pressures to overcome would be the spring of the piston (which only has to be slightly stronger than the atmospheric intake valve) plus the spring of the exhaust valve on the mouthpiece (also very slight) plus the spring of the intake valve of the breathing bag (again very slight). |
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During the exhale, the entire thing is a closed system, so the amount of air that goes into the breathing-bag should be the same as the amount that is exhaled, and (excepting aforementioned valves) not put much onus on the diver than to simply breathe out. |
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I think the difficult part to figure out is that the diver exhales say 100cc, and the breathing-bag is filled by 100cc, but up top 1,000cc of air is being moved... or something like that. |
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Before the gentle whoosh of the piston returning to the left under spring pressure, there will be a violent, almost explosive whoosh as the compressed exhaust air expands until it reaches atmospheric pressure. That is the problem whoosh; the spring powered whoosh is fine. |
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You forgot the part where the diver's lungs are sucked up the exhaust snorkel when the exhaust valve is opened. |
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wait... how'bout filling the exhaust snorkel with water ? |
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that's half the problem solved I think. |
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The other half is put the breathing bag flapper valve up at the top of the intake snorkel. |
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If the piston's traverse completely evacuates the intake manifold into the intake snorkel, then yes otherwise not so much. |
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Assume that air at sea level has a density of 1g/L. If the diver is at a depth of about 10m, the pressure is 2 atmospheres, and air is 2g/L. |
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The diver exhales 1L of air. There is now 2g of exhaust in the chamber to the left of the piston, occupying 1L, at 2 atm. The exhaust valve is opened. *WHOOSH!*. Half the exhaust escapes, leaving 1g, 1L, 1 atm. Whoosh. The spring gently returns the piston. You now have 1g of fresh air, occupying 1L, at 1 atm., in the right hand chamber. Which is not good enough - you need 2g, at 2 atm. |
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Call our existing topside cylinder "cylinder 1". |
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Allow the exhaust to expand into a second cylinder (cylinder 2). Its piston is connected to the piston in a third cylinder (cylinder 3) via a tricksy linkage. The mechanical advantage of the linkage smoothly varies from nearly zero to nearly infinite along its stroke length. Thus: |
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Cylinder 2:
• Speed - slow-to-fast
• Pressure - high-to-low |
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Cylinder 3:
• Speed - fast-to-slow
• Pressure - low-to-high. |
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Cylinder 3 fills cylinder 1 with fresh air. |
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The stale air smoothly expands from 1L, 2g, 2 atm., to 2L, 2g, 1 atm., exerting work on the fresh air, which is smoothly compressed from 2L, 2g, 1 atm. to 1L, 2g, 2 atm.. |
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The movement is spring assisted as before. The result is 2g of fresh air, occupying 1L, at 2 atm. The exhaust air is at 1 atm., and can be vented without loss. The diver only has to do the work of compressing the spring, plus losses. |
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To simplify this conceptually, [cylinder 2 + tricksy linkage + cylinder 3] receives exhaust air from the left side of cylinder 1, and returns fresh air to the right side of cylinder 1, at dynamically matched pressure. The pressure remains slightly higher in the left side (to drive the process), but that differential is provided by the spring. |
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(Apparently, my Words of the Day are "tricksy" and "precious". Gollum, gollum.) |
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Overall it looks like half a breath is wasted each time. If it was a closed pipe that simply arched up, over and back down again, and was connected to the mouthpiece and the breathing bag, then if it were pressurized to the depth it would just be a matter of breathing in and out (except for the eventual suffocation). |
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But in an air replacement system one lungful at pressure of x atmospheres plus one lungful at a pressure of 1 atmosphere = 2 lungfuls, both at a pressure of (x+1)/2 atm. But we still need to introduce it to the depth and that's only going to happen at x atmospheres pressure, not (x+1)/2. |
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On the bright side, [Twizz]'s doesn't work either ;-) |
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On the slightly brighter side, our machinations *will* increase the operational depth of a skindiver to approach twice what it would normally be. |
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On the slightly demented side, an Aquahullaballoon would do exactly what we want. |
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That'd be one helluvahullaballoon. |
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Has that been discussed before? An underwater hullaballoon would not require the lifting gas to be pumped among the balloons, as their size variation would be caused directly by the pressure gradient of the water. If that's what you were thinking, please post! If not, may I have the honour? |
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looking forward to reading it. |
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LOL... except you didn't mention it's usage for breathing underwater which, umm what I was thinking. |
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I figured that was a separate idea. However, as you wish... |
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//Snuba//
When I first read about Snuba (many years ago, in some science magazine...), I hoped it was an acronym for Surface Nurtured Underwater Breathing Apparatus. Seems it's just a boring combination of snorkel and scuba. |
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