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Breathe Under Water Without Oxygen Tanks
Charlie Paglee writes "An Israeli inventor has developed a way for divers to breathe underwater without cumbersome oxygen tanks. His apparatus makes use of the air that is dissolved in water like the gills of a fish. With patents in Europe and the USA how long will it take for someone to use this to swim the English Channel underwater?"
Now you just need some batteries: "Calculations showed that a one kilo Lithium battery can provide a diver with about one hour of diving time."
Does that make it lighter or heavier than existing oxygen tanks?
Sounds to me like a job for nuclear-powered batteries.
Usually inventions only come about when the underlying technology is improved to the point where the new invention is feasible (i.e. made possible by faster processors, stronger steel, etc).
A look at the article reveals that the main components in this invention are a centrifuge to adjust pressure, and a battery to power said centrifuge. Both of these components have been around in usable form for decades at least.
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That is a bad report.
SCUBA divers used compressed NORMAL air in the tanks. You can dive safely down to 50 metres on that (this is nothing to do with 'the narks yet').
Profession divers, usually military types (Royal navy etc.) use compressed air to deeper depths (70 metres).
The problem comes when the ratio of oxygen is greater than normal) - you can die of oxygen poisoning - hence why saturation divers have to breathe a reduced mixture of oxygen with nitrogen.
So, this is great for the pure rebreathers, but not for the common man if it do9es just extract pure oxygen from the water.
I once ran out of air at 70ft because of a faulty pressure gage. And that's pretty simple technology. No big deal if you stay calm and remember your training because there is still air in the tank (gage read 500psi, pressure differential was 0, actual pressure was around 40psi).
I'm going to be a little hesitant with batteries. It's enough trouble tracking rechargable AA and laptop batteries. Now you'll need a reserve battery (for your reserve air) and it better darn well be healthy! A pressure sensor is a lot simpler than something that calculates remaining charge.
Still, I have no doubt they'll figure out how to make it robust enough for us casual divers in the next 10-20 years. 'Til then I'm going to stick with the malfunctions I know how to survive.
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I don't see how the contraption can both be small and deliver at a high pressure while operating off of one battery.
Because you're already at that pressure, any device will produce O2 at that pressure. It would actually be *harder* to get it atmospheric pressure.
Also, now that I think about it, I think the US navy has some pure O2 underwater low depth breathing rigs like this.
I don't think anyone uses pure O2. When going past a certain dept, I think it's mainly a O2 + Helium mix, hence divers sounding like Donard Duck.
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What happens when you hit a patch of oxygen poor water? Better have some reserve oxygen in the design just in case.
Looks like your really trading an oxygen limit for a battery limit.
A centrifuge. Ah, wonder what the trade off is between swimming with a heavy tank and swimming with a spinning mass are like. Hope the moment of inertia isn't too big.
Wonder what other gasses you'll be collecting from the ocean along with your oxygen. Might not want to use this baby around any volcanic vents and such.
It's safer if you maintain a dive profile that always allows you to return straight to the surface.
So the fact that this device could allow you to maintain at 30 or 60 feet for the 30+ minutes it might take to safely decompress on the way up isn't likely to change the rules for recreational diving.
Now it may be a big advantage for commercial or military diving where the divers are professionals and are willing and able to do dives that require mandatory decompression stops..
Except that recreational SCUBA diving, like the grandparent post is referring to, is designed to avoid a decompression stage; both because it is an easy thing for recreational divers to forget to do / skimp on, and because it affects the ability to deal with any emergencies that might arise while underwater.
While that is true I still think it will find purchase in recreational diving.
The concern about casual divers running out of air is a big part of choosing a no-decomp dive for everyone, and for semi-advanced groups you could arrange a nice dive that went deeper for a while, then shallower for a while, until they could go back up.
Another major benefit is no more problems with heavy breathers which can terminate a dive early and really throw off plans of a dive group, which is another reason I think it will be quickly adopted even if it's not used for longer dives. It finally lets people dive as long as they are supposed to without tank capacity being a limit.
And yes, on some of my first dives I was one of those people that chewed through air way too quickly. It came from trying to also do underwater photography right off the bat before I was comfortable with boyancy and as a result I used a lot of energy (and thus air) maintaining depth. I don't make that mistake anymore!
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Of course, one has to wonder if said oxygen tank will allow you to properly decompress in time. Of course, when faced with running out of air, the bends may be the least of your worries.
With recreational diving, also called no-decompression diving, the idea is that you can immediately return to the surface at any point. Usually, we take a 3-5minute decompression stop at 15', just as a precaution.
To get certified (with PADI anyways) one of the things you have to do is a controlled emergency ascent (which is basically your worst-case solution if you run out of air). You actually have enough air in your lungs that on a full breath you can quickly (at the speed of bubbles) swim to the surface and you will be able to slowly exhale the whole way, since the air expands as you go. Of course, if you do this from below 60' it would probably be a good idea to go to a decompression chamber to be sure. We had to do it from 30' I think, and it was by far the least fun thing in the checkout.
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You don't really have to worry about the divers breathing pure oxygen. They won't be. They'll be breating a mix similar to air.
The process of lowering the pressure around the seawater will lead to the release of all disolved gasses, not just oxygen. I didn't notice anything about a co2 scrubber, so I think its safe to say that the inhaled gasses will be similar in content to whatever is disolved in the ocean.
At atmospheric level, air is: ~73% nitrogen, ~23% oxygen, ~2% carbon dioxide, ~2% other, if I recall correctly, and I don't think that the solubility constants are signifigantly different in salt water to throw off those percentages that much. If anything its probably less rich in oxygen and more carbon dioxide enriched at greater depths due to marine life respiration.
With a system like this, it might even be possible to remove some of the nitrogen from the breathing mix with a second step. This would allow unlimited dive times without the nitrogen buildup that results in the bends if you stay down too long.
We (divers) do not breathe pure O2 for the working portions of our dives. We do use it during the decompression portion of our dives. Keep in mind though that recreational divers DO NOT ever use pure O2 for any part of their dive. You can get trained as a rec diver to use 40% 02 MAX, and definitely not for doing deco.
Oxygen becomes potentially toxic when the partial pressures is beyond 1.6ATA. For 100% O2, the depth limit is 20 feet. For 50%, it's 70 feet. At 32 feet on O2, you are getting very close to needing your partner pull you up and hold your regulator in your mouth until the seizures stop and you come to.
The Navy, as well as many civilians (and my friends...) have what you referred to as "low depth breathing rigs". The pure O2 ones went out of favor a LONG time ago...they were most famously used in the human-torpedoes during WWII I believe...the biggest problem with them is that as the soldiers were piloting the torpedo, they would go to deep, pass out and never return.
Today, rebreathers are used. There are both closed circuit or semi-closed circuit. They ARE NOT using pure O2. Depending on which rebreather you have, a variety of gas can be used in the breathing loop - air, nitrox or trimix. What the rebreather does is keep your breathing gas at a constant partial pressure of 1.4, thus minimizing as much as possible your inert gas loading to reduce your decompression obligation. Essentially, as you go deeper, the gas you are breathing contains less oxygen.
Can we stop talking about "replacing Nitrogen with Helium." This is wrong for two reasons. First- it isn't completely replaced as people keep implying- Helium is added to Nitrogen and Oxygen forming Trimix. It would be hard to call it Trimix if you didn't have all three. Second- The Helium replaces the Oxygen not the damned Nitrogen. The point is to get rid of the Oxygen which becomes more and more toxic the deeper you go. Nitrogen is still there.
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Actually, pure O2 is toxic at 1 ata (ppO2 1.0). Anything beyond somewhere around 25% O2 will give you "full body oxygen toxicity" if exposed for long enough.
Also, modern rebreathers have no problems delivering the required pressure (which is delivered at ambient). The single biggest limitation on rebreathers (after scrubber life) is the diver. Nobody wants 6+ hours in the water, where 5.5 hours is on deco.
If you extract dissolved gas through a centrafuge, you're going to get all the gas in the water. This may or may not be analogous to just "air".
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Secondly, by creating the gas under varying pressure, you are dealing with a complex concept:
- The mechanism creating the gas must work with (an almost static) pressurized fluid - water as input.
- After sealing and then while spinning, the gas inhabits the area nearest the axis, and floats up to the top of the chamber. The water is in a vortex. The attitude of the chamber distorts the shape of the vortex and changes the rate gas can be extracted.
- After spinning, the gas must be collected without including the water. This would then be pumped into a chamber for storage.
- Defeat the consumption of gas in the storage chamber. At depth, less gas is dissolved per unit of fluid, and this make the aparatus worker harder to keep up. Also, your "dried" water source must be flushed.
- Key to this would be a constant-fed system that kept spinning while accepting fluid and delivering gas. Side issues are the buildup of sediment (while gas is being separated, so are things heavier than water), and the seawater encapsulation issues
- You can enter "dead zones" in open water, where the type or amount of dissolved gas is not able to support life. This would be a big danger. One's storage mechanism would need to cover for just such an emergency. Enough to surface, with decomp time if warranted.
Personally, I think they should research more into completely bypassing lungs in the system. Folks could elect for bypass surgery that installed a machine in their chests, and blood would undergo the CO2/O2 exchange in the internal machine. The machine would expose plugs to the skin, and rechargeable devices could feed the required gasses. The ingredients could be varied based on heart rate. Stopping the breathing reflex may not be possible, so a small mouth-based device might be necessary (just an unprocessed recirculation system). The volumes of gas we're talking about in this instance are much less than lung capacity. Also, compromised lung function (through smoking/pollution/defect) would not apply.
The physiological effects of the human body underpressre are numerous. Different topic entirely
Not exactly. I am a PADI diver(judge that as you will), but I am pretty sure that NAUI also teaches no deco diving. In PADI, all normal rec diving is considered to be no deco. We learn to deal with it if needed, but are discouraged from actually exceeding the limits. That is left for later certifications. We did a deco dive when I was taking my advanced open water course.
Now, some people have a problem with PADI's philosophy and style of teaching(I sure do), but I think their stance on no deco rec diving is fairly average for the recreational diving industry.
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And yes, on some of my first dives I was one of those people that chewed through air way too quickly. It came from trying to also do underwater photography right off the bat before I was comfortable with boyancy and as a result I used a lot of energy (and thus air) maintaining depth. I don't make that mistake anymore!
Newbies can get in a bind pretty easily too. I had a regulator malfunction at about 80 feet diving a wreck. It spewed air, which wasn't so bad for breathing (I've had them ice, which is much worse), but by time I did my ascent and was able to turn off my tank it was pretty much empty. The boat was a good 1/8 mile away and there were 7 foot seas. Yay. The divemaster was already around the ship so he didn't notice (perhaps he should have).
Fortunately I had grown up spending my summers in the ocean and had trained as a Boy Scout lifeguard (3 2-mile swims a day) and was trained to dive by a mean old Libertarian from Vermont so I was able to get back to the boat without air (it's a bitch swimming on the surface in full dive gear). But I can easily imagine less fortunate outcomes with your average cruise-ship certified diver.
Having an essentially limitless supply of air would let him hang neutrally boyant just below the surf for a very long time, at least long enough for a divemaster to figure out where his diver went to. I don't have my charts handy but he could probably hang something like a couple hours without too much risk of pressure sickness. Heck, if were small enough might as well carry one as a backup on SCUBA dives.
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Having dived since '73, I agree with most of what you said. However when tanks get empty they are lighter than when full. Weigh yours empty then full. That was never a big problem with the old steel tanks but with the advent of aluminium tanks the weight change was noticeable, that is why the bouyancy compensator was invented. With steel you went down about 2 LBS. heavy and were neutral to positive when it was time to go up. I still have my original U.S. Divers 72 Aluminum tank. It has about a 6 LB. difference full to empty. That is a bit much to deal with without a BC. The BC works just like the trim tanks on a sub. Instead of adding or subtracting water, you do it with air to maintain neutral bouyancy. That way you don't waste energy trying to maintain depth, which burns up the air supply faster.
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The usage of "Nitrox" for sport diving is oxygen RICH mixtures, generally 32% or 38% O2 for recreational diving. The advantage is less nitrogen absorption, therefore longer no-decompression times. As others have pointed out, the disadvantage is depth limitations due to oxygen toxicity. A partial pressure of 1.4 atm O2 is the general "do not exceed" limit.
I am nitrox certified and experienced in making, testing, and using my own mixes.
A closed circuit rebreather that I have been trained on (by an ex Navy SEAL) maintains an oxygen partial pressure of 1.2 atm. The practical limit on dive time with that particular rig is cold or boredom.
Raising the % of Nitrogen (and therefore the partial pressure at depth would be insane, as you'd get a double whammy of increased nitrogen absorption causing both shorter bottom times / greater decompression requirements, and increased likelyhood of nitrogen narcosis. That is why mixes used for sustained dives below ~150 ft. use Helium, Argon, or other gases for the "bulk" in place of Nitrogen. These have other, different side effects that have to be dealt with. "Mixed Gas Diving" if I recall the title correctly is an excellent book on the topic.