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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?"
"There are a number of limitations to the existing oxygen tank underwater breathing method. The first is the amount of time a diver can stay underwater, which is the result of the oxygen tank capacity."
I have scuba dived since 1982 and I am rarely limited by the amount of O2 I have handy. The limiting factor for any diving to any real depth (>30 feet say) is the amount of residual nitrogen in your blood stream. If that gets too high, and you surface, you get what is commonly referred to as the 'bends'; little bubbles of nitrogen bubbling out of your blood stream. Bad news. This is true for recreational diving anyway. The military, deep sea welders and others with decompression chambers might not have this problem.
The other big drawback I see is that at depth the pressure of the water on your body is very great. That is why modern scuba uses pressure delivery systems. That is, they deliver air at a pressure that is near to the surrounding pressure. This makes it so you can actually draw in a breath of air given all the pressure on your chest (and hence the 3000 psi scuba tanks). I don't see how the contraption can both be small and deliver at a high pressure while operating off of one battery. Even at ~32 feet you are at 1 atmosphere extra pressure.
Now, it may very well be great for submarines, but I don't think it will be useful for scuba.
Also, now that I think about it, I think the US navy has some pure O2 underwater low depth breathing rigs like this. The big advantage of those is that they produce no bubbles. Very stealthy.
Pure O2 is poisonous below about 32feet, if I remember correctly and if you go below about 100feet, just depending you can get high. Go google, "rapture of the deep."
--greg Vulcan quiescent... Q: What machine shutdown with this message?
We had gas diffusion processes working since the 1960s with GE putting a parakeet into a box, then putting the box into a freshwater aquarium.. The 'keet breathed air being passed to it via a 6"x6" piece of membrane.
Now the problem was the rate of diffusion, how much gas will the membrane allows to pass within a given time. The demo GE put on was fine and dandy since the bird's O2 demands were so low. But with a living, breathing, working mammal, thats a whole different kettle of fish.
I hope that the Israeli understands that before he scales up, or he might wind up agianst a dead end with the project.
First rule of holes; When in one, stop digging.
to swim the English Channel underwater?"
Probably never.
Swimming underwater will take a great deal more effort since more body frontal area is exposed to water, which is denser than air. You will also have to expend more energy to either a) stay submerged, since you would be fighting your positive buoyancy or b) dragging along more weight to stay neutral buoyant.
"Eve of Destruction", it's not just for old hippies anymore...
I have scuba dived since 1982 and I am rarely limited by the amount of O2 I have handy.
Because I like decompression diving, air supply is still the number one limiting factor to my dives. I still don't think this will be useful.
That is why modern scuba uses pressure delivery systems... I don't see how the contraption can both be small and deliver at a high pressure while operating off of one battery. Even at ~32 feet you are at 1 atmosphere extra pressure.
I call bullshit! First, pressure delivery systems are a direct consequence of storing air under pressure na d the reason why that is done is the convenience of have all that air in an itsy bitsy bottle! Second, the contraption will automatically create air at ambient pressure (which is all you need to be able to breathe). Third, at 10m (~33 ft) you are at 2ATM pressure, not 1ATM!
The main reason this is useless is due to the following calculation... At the surface, 1 ATM, to fill one one shallow breath (~3 litres) you would need to process 5 / 0.015 = 200 litres of seawater. Take that down to 20m (66ft - 3 ATM) and that becomes 600 litres, because the gas compresses under the pressure of the water. Now consider that a relatively fit adult might have as many as 15 of these breaths a minute! - 9000 litres a minute of seawater!Do a relatively technical dive down to 50m (6ATM) and I reckon the guy using that kit would be picking his buddy out of the water inlet!
Additionally,
Pure O2 is poisonous below about 32feet, if I remember correctly and if you go below about 100feet, just depending you can get high. Go google, "rapture of the deep."
1) This system extracts AIR, not oxygen. 2) Oxygen has little to do with nitrogen narcosis, aka "rapture of the deep".
I'm very sceptical that this device will be much use . One of the primary reasons for breathing compressed air is so you can actually take a breath at depth.
You increase the ambient pressure one atmosphere (14.7 psi) every 33 feet in salt water (34 fresh water). This extra pressure makes expanding your chest cavity to take a breath very difficult without a high pressure source to breath off of. The whole reason for the first stage of any regulator is to match plus 1 or 2 psi the ambient pressure to compensate for the squeezing pressure on your chest.
At anything below 33 feet your going to expend most if not all of your energy just trying to take a breath.
CO2 becomes toxic at about 4%. Thats why there are scrubbers.
-Joey
The parakeet thingy was demonstrating passive diffusion. This isn't the same.
If you RTFA you'll see that his technique is active. The gas is physically extracted from the sea water using a centrifigul pump to lower the pressure and let the gas bubble out like foam from a coke.
It's quite clever really.
A typical open water scuba tank (aluminum 80 ft^3) will weigh about 40 lbs (mass 18 kg) and will last a typical diver a little under hour at 30 ft. or 25 minutes at 100 ft. (assuming ideal tanks and breathing the thing down to "zero"). Since this device appears to be mostly void space (it's a turbine that will be mostly full of water during operation right?) It probably is pretty light (it does not need to be neutrally buoyant when empty: it'll fill with water at the dive site.)
Extending bottom time with a typical scuba tank involves bringing ever heavier tanks with more air. (or risky rebreathers.. they are at least as complex as this device appears to be from the article). This system appears to have some of the same advantages as a rebreather: namely that volume of gas available is not dependant on depth. This is a huge advantage for deep dives. It also seems to avoid some of the more worrying dangers of rebreather operation: there is no CO2 removing compound to react poisonously with water in the event of flooding, the O2 partial pressure is almost certainly above the minimum requirement for life (though must still be monitored). It introduces other dangers which must be evaluated: parts moving at high speed which could fail, does not have the favorable buoyancy characterists of a rebreather (each breath, buoyancy varies by the volume of O2 consumed rather than by the volume of an entire breath)
I would imagine that this would be about the same weight as a similarly capable rebreather assuming the 1kg/hour marginal weight cost. A typical laptop battery is a little under a kilogram. It would seem that the fuel-cell replacements for same would be a pretty good fit here (few moving parts, high energy density, relatively low power) Though it would add additional complexity. I'm not sure I'd want to have my primary breathing gas dependant on a battery that loses capacity as quickly as LiIon though.
Can you be Even More Awesome?!
I'm also a longtime diver, and the article struck me as silly.
As you note, nitrogen saturation is our primary limitation at depth. There's Nitrox and Trimix, but exotic gasses are only so useful. This proposed breathing system seems to be proposing a high-oxygen mixture. Oxygen becomes toxic at high doeses. Fabulous.
My favorite part, though, is the claim that tanks become "unbalanced" as they empty. I've never noticed this effect.
This is my post. There are many others like it. If you don't like what you read here, go try one of the others.
Read the patent - this baby has to pump 2000 liters a minute through its gas separator. It even proposes that the expelled water can be used as a propulsion system.
Im thinking that 2000 liters a minute is a huge amount of water moving power. Maybe equivalent to the output of a jet boat.
Nice thing to have strapped to your back. Probably need to carry along enough oxidiser to make it run for any length of time. Doh!
Nitrox has a higher percentage of Nitrogen, not oxygen... the point is to keep the partial pressure of oxygen at high pressures at a level that is less than toxic. to do that you have to decrease the percentage of oxygen in the mix.
Other mixes use varying levels of inert gases. according to one text i read not too long ago, the most effective to use, interestingly, was argon; i would have expected it to be either helium, as the lightest, or to increase in effectiveness with atomic weight.
good point about the ambient pressure... rebreathers have actually been used to set world record depth dives. incidentally, the guy that taught me to dive at one time had the world record for deepest non-recycled dive (meaning they were switching out tanks with special mixtures as they went down.) when you're doing dives like that (I think he got to 987 ft.) you almost literally have to invent the science as you go--there's very little published literature on what will or won't kill you at that depth.