Free-diving, artificial gills, and seasteading
August 5, 2011 at 1:01 am #1575
Okay, so I read a BBC article just a few minutes ago while searching for “artificial gills”. This after I watched some videos on YouTube about Freediving, Finswimming and Monofins. It has all brought me to an crazy idea. You see, this scuba diver in the article is downing the technology, saying he wouldn’t use it without backup. However, I think it would be the perfect tool for free-diving. You could stay down twice as long, though you would still have to go on the buddy system in case of a blackout.
If you can learn free-diving, you could learn to take care of fish cages without scuba gear. All you would need is one of these “artificial gills” to give you air from time to time, and you would be able to do what you need to do without scuba gear. Again, it might be dangerous due to the possibility of blackouts, but it is a technology that would help seasteaders in a whole lot of things, the least of which would be the underwater inspection of their seastead.August 5, 2011 at 8:14 am #14589
I am interested… Would you please provide a link?
Never be afraid to try something new…
Remember, amateurs built the ark, professionals built the Titanic.August 5, 2011 at 5:32 pm #14592
Just click on the words “BBC article” above. That’s the link.August 10, 2011 at 7:43 am #14608
I remember talking about this stuff in past, it isn’t yet as practical as most people think it is, it can’t be carried on person yet, it requires constant amount water to run through the system with a certain speed so it is more like to be applied in submarines and perhaps in habitats underwater which can be built on underwater walley with fast currents to save energy(though it is effectiveness would probably decrease dramatically in deepwater). Though it is an intruging subject.August 10, 2011 at 1:51 pm #14615
the key is in the article
…..circulate around 200 litres of water per minute to accommodate the breathing needs of an average person…. circulate a bathtube of water per minute is a lot of energy – there are easier ways to get breathable air to underwater living space.
See Lloyd Godson and his underwater habitats – he made it with a barril sized algea tank …interresting for a space habitat – but even so – a snorkel is still a lot easier -
Why bother, when there is lot of breathable air that just needs to be sucked down from the surface by a ordinary tube ventilation sistem as a performed in any highrise building, tunnel, subway, ventilation sistem.
concretesubmarine.comAugust 12, 2011 at 2:37 pm #14639
Well yeah, its unproven technology (in the field). I’m sure they will work on it. However, I do think that if you learn free-diving, this would be a great tool, as you will only be respirating once every few minutes. It would greatly extend your dive time.August 13, 2011 at 10:36 am #14646
As we move further and further into an aquatic based living environment, rather than a terra based one (and I would that even the most avid sailors are still primarily terra based) we will come across innumerable scenarios for which we have failed to account. The best we will be able to do for all of these unforseen possibilities is to prepare ourselves strategically rather than tactically, so to speak. In other words, rather than seeking to solve specific problems that may or may not come up, we would be best served by arming ourselves with tools that can be implimented partially or completely in tackling a broad range of issues. It’s quite obvious to state this, but we are going to be doing a LOT of diving for various reasons once we live fully at sea, and we will want tools to equip us for such.
In that manner I think this technology is fantastic. For right now, and for what you have suggested above, the essence of which seems to be extending dive time without the use of the traditional bulky gear of a scuba diver, I dont think it serves our purposes very well; certainly not as well as something like this, which can be easily refilled and reused. Of course, as stated in the article, the device itself is young and has a great deal of growing up to do. The more generations a device grows through, the more it shrinks, grows in power, and adapts to specific situations. Being what it is, a device that allows you to use the oxygen where you are rather than bringing it with you, I think its probable future version is so valuable for personal diving that this is one tool which we would be foolish not to latch onto. And besides, given the Law of Unintended Consequences, who knows what other uses, techs, procedures, or whatever else may come of it.August 14, 2011 at 12:59 am #14649
Traditional bulky gear of Scıba diving? This technology is actually far more bulky than traditional gear.August 14, 2011 at 6:36 pm #14652
I was referring to future iterations of the technology – meaning that seemed to be what some of the people above thought of as it’s goal – and I was saying that it does not serve that purpose now (since it is, as you pointed out, more bulky) as well as the phantom tank to which I linked.
ah, the failings of textual communication.August 14, 2011 at 8:17 pm #14655
Recirc diving gear need not be bulky, it’s a matter of using smaller components. I’ve seen pics and vids of homemade rebreathers that might weigh in at 2-3 kilograms…
Never be afraid to try something new…
Remember, amateurs built the ark, professionals built the Titanic.August 14, 2011 at 9:46 pm #14656
And thats exactly the kind of thing I was referring to that better serves the purpose of allowing a diver to achieve longer submersion times without the necessity of full gear.
I guess I must have been vague with my speach. What I intended to say, boiled down to its essence, is that this is a great tech to keep working on for future use as a tool for all sorts of problems, but not for what some people seem to have been suggesting for use right now.August 18, 2011 at 6:53 am #14760
I assume you’re saying just for going down and for instance repairing holes in the nets (or i suppose cages if you’ve got real shallow water or a naerby source of scavenge metal) you use to corral your fish you’re farming? Like just giving a couple extra seconds or minutes of air. But for this purpose why couldn’t you just use a tiny bottle of oxygen? I mean, say a little bottle that just straps to your chest with a mouth piece hanging off, you take one breath every thirty seconds or so (maybe more for when you’re working hard), even a bottle the size of one on a paintball gun should have enough for several breaths or more (never done scuba, though I want to learn, so I’m not sure how many cubic centimeters at stp you fill your lungs with, what pressure the tanks are at, etc). Then you could just build a float with a little motor/air compressor on it (or oxygen collector) that you float up above you on the surface, with an anchor or tiny placekeeping motors if its too deep (or just secure it to whatever keeps your cages/nets in place) and have several bottles. You go down, work however many minutes on one, then simply go up and plug it into one of many charging ports on the floating compressor and take out a fresh one.
Seems like it’d be cheaper to set up than scuba or one of these gill dealies if you’re just looking for decent spans underwater. Though a really compact rebreather would obviously be optimal. Seasteads will probably pretty quickly generate tech like that, especially if you manage to put it somewhere with some shallows where people can do spearfishing, diving, coral culture for increasing the local fish populations, etc.September 7, 2011 at 10:33 am #15302
Since joining this board some time ago, I have gone through PADI scuba training (Open Water, Advanced Open Water, and Enriched Air) and I have about 3 dozen dives under my belt now. I joined a dive rescue team and trained in Emergency Response Diving (ERDI)… I’m not the utlimate expert, but I am aware of some things some of you are evidently not.
An average scuba tank is 11 liters (80 ft3) and pressurized to 200 bar or about 3000 psi.
An efficient swimmer avoiding heavy exertion, at shallow depths (less than 20 meters) may last up to 2 hours under water (I am talking very generally). Most new scuba divers are lucky to get 50 minutes. 35 minutes is not uncommon for new guys, due to inefficient swimming, excitement/fear, and inability to contrl buoyancy. Women typically do better than men. Start doing any work whatsoever, and the time you have drops drastically. Get into colder water, time drops drasically. Go deeper, time drops drastically.
A Scuba destination seastead on a seamount that has been cultivated and groomed could be a fairly lucrative operation, if you’re willing to become a primarily service economy. Scuba gear does have moderately high costs both to purchase and to maintain.
For a working seastead with some kind of industry that requires a lot of time underwater, it would almost certainly be surface-supplied air.
Professional diving is almost all done with surface-supplied air. When working, it simply isn’t practical to carry enough air- the tanks are too bulky. Another issue is warmth. Even in the tropics, water temperature is generally less than body temperature. Working under water is strenuous and less efficient than working on land, so therefore more exhausting.
Surface supplied air allows you to constantly refresh the air supply, and to help with temperature issues as well. It has its limitations in mobility as a trade-off. Surface-supplied air can be supplemented with a “pony bottle” for emergencies, but the problem with extended bottom time on surface supplied air is that decompression times can be significant before you can return to the surface. Deco time is a factor of both depth (pressure) AND bottom time.
Every 11 meters or 33 feet, adds another atmosphere of pressure. At higher pressure, nitrogen is absorbed into the bloodstream, where at the surface it is simply exhaled. If proper decompression procedures and times are not adhered to, upon ascent, that nitrogen will no longer dissolve in the bloodstreem, but will form bubbles. These bubbles cause decompression illness, or “the bends”. Bubbles in your bloodstream and joints are NOT good for you.
So suppose you simply eliminate the nitrogen (78% of normal air) and go with straight oxygen (21% in normal air), the newby asks?
Well, at higher pressures, oxygen is toxic. Higher concentrations effectively the same. Combine higher pressure with higher content, and there’s a steep toxicity curve, that can cause convulsions. Bad enough on land, deadly under water. There are strict depth limits with tables that chart out safe levels of oxygen percentage per each maximum depth. Recreational Scuba tops out at 40% oxygen, and anything over that may void the warranty on your equipment, because the higher oxygen content is corrosive to the gear. Even at recreational scuba concentrations under 40% nitrox (enriched air) requires specially-cleaned tanks and careful handling. For 100% oxygen- the rule of thumb is no more than 20 feet (just over 6 meters) and it’s really only for emergencies, in special delivery systems (not so super-high-tech, just distinctly marked and carefully handled). There’s also a table and calculation available for how much oxygen exposure is safe over time- it is possible to exceed this safe oxgyen exposure cumulatively rather than acutely.
So the area in which you’re diving, having a variable amount of oxygen in it, would be impossible to predicton the fly for safety margins. It would vary with depth, temperature, level of sea life, area of the world, etc. You risk having too high a percentage of oxygen, as well as too little. In a stationary environment with redundancy built into the system, with measuring and metering equipment to guarantee the safety of the air you’re breathing, this could be a very useful technology. Otherwise, a traditional scuba rig rebreathing apparatus is much better. Rebreathers also require special training because of this combination of oxygen toxicity and nitrogen issues.
Regular scuba just stores air (or some version of air with more or less oxygen in it depending on your dive plan) you take a breath from an on-demand regulator, and exhale it out into the water. This is pretty wasteful, because we don’t metabolize all the oxygen in a normal breath of air. Our reflex to breathe is triggered by CO2, not by lack of O2. So we’re exhaling MUCH more O2 than we absorb. At depth, under pressure, the air we breathe is much more compressed- more molecules per volume, but we still only have a fixed amount of surface space in our lungs on alveoli to exchange O2/CO2. So even more goes to waste at depth. One lung-full at the surface equals twice as much at 33ft/11m, 3 times as much at 66ft/22m, 4 times as much at 99ft/33m and progressively on. Recreational Scuba depth is considered to max out at 140ft on standard open circuit scuba gear without special gas mixes and training.
A re-breather re-circulates the air we’re exhaling, scrubsthe CO2 and then we breathe it again on successive passes. Constant monitoring and adjustment of the mix is possible, and more or less mandatory (I am not trained on this gear.)
For technical deep diving (below 140ft), there are other gas mixtures, but these are not cheap or trivial to produce on a remote seastead. They also require specialized training and equipment.September 7, 2011 at 11:45 am #15303
Well yeah, its unproven technology (in the field). I’m sure they will work on it. However, I do think that if you learn free-diving, this would be a great tool, as you will only be respirating once every few minutes. It would greatly extend your dive time.
I think you’re over-estimating the benefit of free-diving and under-estimating the risk. Youo can’t really accomplish “work” while free-diving. At best you can pick something off the bottom and return to the surface. Most people cannot hold their breath for a full minute. Really experienced divers get several minutes of dive in. Part of the reasaon they can do this is because once you hit 33 ft, the air in your lungs is compressed to half the volume, so it’s not as hard to hold in- you constantly release a few little bubbles all the time, which helps with eliminating the CO2 which is triggering your reflex to breathe.
Free divers pop down (harder than you think when holding full lungs, you have to use a weight to assist) look around for a few seconds, and come back up. You’re not going to get much deeper than 20-30 feet, maximum. Pearl divers did this when there were no alternatives, but it was an arduous and dangerous lifestyle.
Something people don’t realize about diving is that even shallow diving is dangerous. The difference between the surface and 33ft is the steepest pressure gradient. This is somewhat counter-intuitive, so it is important to grasp it thoroughly.
0ft – 33ft is a change between 1 atmosphere and 2 atmospheres. That is 100% change
33ft-66ft is a change between 2 atmospheres and 3 atmospheres. That is a change of 50%. It’s 150% of the surface, but from 33ft-66ft it’s only 50%.
So popping back and forth betweeen 0ft and 33ft produces the greatest physical pressure changes in your dive. Repeatedly doing so is as dangerous as ascending too quickly from a greater depth. Doing it as fast as required for free diving (because you’re out of air) is even worse. Adding more air to your dive while on the bottom, increases the time for nitrogen absorption, but people would still push their limits and need to pop back up quickly when out of air. You can greatly reduce your risk of decompression illness by following tables, using dive computers, etc.
One thing that is best practice for scuba divers is to always perform a 3 minute “safety stop” at 15 ft (5m) for 3 minutes at the end of the dive. We always budget air for this. This is not a deco stop- it’s only a deco stop when tables or computer indicates it’s necessary, but it is a belt and suspenders safety practice for avoiding decompression illness and injuries. If I’ve been below 20 ft, my dive computer automatically prompts me for a 3 minute safety stop. Your whole free dive is unlikely to last more than 3 minutes, especially not your descent and ascent. You’ll want as much time on the bottom to accompish your task as possible.
Avoiding multiple sudden pressure changes is one of the best ways to reduce your risk. Free-diving all day long every day is a good way to get bent, and have sinus/ear pressure injuries. But individuals are individuals and you cannot completely eliminate all risk. It depends on your physical state, and environmental factorsDecember 22, 2011 at 12:17 am #16900
I hear what you’re saying. But really. How deep will you be submerging fish tanks? How deep with the deepest one get? If you bring it to the surface, then dive into it, then you aren’t going to dive as deep. What’s more, I spoke of free diving, but what about spearfishermen? They use the concepts of free diving, while at the same time doing work (killing fish). Free diving came from oyster divers, who apparently discovered the ability in the first place.
If we’re talking about doing repairs, then yes, use the scuba gear with surface air pumped into it. But if you are simply inspecting fish pens, or the underside of the seastead, all you’re really doing is swimming to the depth of the bottom of the seastead. Take a camera with you and snap a few pictures from each viewpoint, then surface, and you can get a good idea of what is going on. If you see something you need to look at closer, you dive for a better look, or dawn the scuba gear and do some work.
Harvesting fish in a fish pen is really no different than spearfishing. You could use the same techniques free diving spearfishermen use and get along fine.
You must be logged in to reply to this topic.
Posted on at
Written by shadowmane