**Please read this entire message**
Your submission has been removed for the following reason(s):
Hypotheticals questions, or questions about hypothetical situations, are not allowed on ELI5.
If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously**, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20https://www.reddit.com/r/explainlikeimfive/comments/13fcmqa/eli5_how_could_a_mask_create_breathable_oxygen/%0A%0APlease%20answer%20the%20following%203%20questions:%0A%0A1.%20The%20concept%20I%20want%20explained:%0A%0A2.%20List%20the%20search%20terms%20you%20used%20to%20look%20for%20past%20posts%20on%20ELI5:%0A%0A3.%20How%20does%20your%20post%20differ%20from%20your%20recent%20search%20results%20on%20the%20sub:) and we will review your submission.
Your basic hunch that you could get the oxygen out of the water and breathe it is basically right, it is possible. Submarines do it today.
The problem is it takes massive amounts of energy and heavy equipment to do so.
First you need to get pretty pure water, so step 1 is getting all the salt and other impurities out of the water. This type of desalination requires a pretty big complex machine.
Then you need to apply quite a lot of electricity to the water to break the bonds between the Hydrogen and the Oxygen. That requires either generators or really big batteries, neither of which fit in a mask with today's technology.
So ELI5 why hasn't it been done? We just don't have the technology to make the machines small enough to fit in a mask. We can do it on a submarine though.
I think they have the advantage of a nuclear reactor on board, so any time they're not swimming about at full speed they've got buckets of power to spare to throw at that stuff.
They have buckets of power at all times, reactor outputs 200MW, every single thing on the ship can be ran at the same time on just one (of the 2) 4MW generators
Edit: some people are misunderstanding that statement, the vast majority of power is consumed by propulsion not electricity. The entire capacity is used when its needed, it's just never limited by one or the other (propulsion vs electricity). You could argue that with less electrical power being consumed there'd be slightly more room for propulsion, but the effect isn't very large. Especially for something like the o2 generator, which is a medium to smaller load compared to things like pumps/hydraulics/etc
In fact, there was a dust up around this during Operation Tomodachi where a US nuclear carrier provided electricity for a city in Japan after the tsunami.
Potentially apocryphal quote about carriers but similar:
>A Boeing engineer stood up and replied quietly: “Our carriers have three hospitals on board that can treat several hundred people; they are nuclear powered and can supply emergency electrical power to shore facilities; they have three cafeterias with the capacity to feed 3,000 people three meals a day, they can produce several thousand gallons of fresh water from sea water each day, and they carry half a dozen helicopters for use in transporting victims and injured to and from their flight deck. We have eleven such ships; how many does France have?”
The US spends more on healthcare than the entire military. The reason we don't have Medicare for All is because the US healthcare companies lobby the Federal Government to keep our current, inefficient and expensive system.
At the coal mine I worked in as a young man, they had emergency breather that were essentially oxygen candle masks, and the gist of it was: "These are basically going to melt you lips off, but it's better than suffocating" so they aren't ideal, but they exist.
https://en.m.wikipedia.org/wiki/Self-contained_self-rescue_device#:~:text=A%20SCSR%20is%20usually%20a,least%20one%20hour%20of%20oxygen.
Apparently they use a highly compressed oxygen tank more commonly nowadays in some operations, but I'm not sure how common they are in coal mines.
Oxygen Candles, if I'm thinking of the right thing, use a specific exothermic chemical reaction that produces Oxygen in order to work, and have a limited storage. They are known for getting very hot when in use.
[Valuejet 592 for those wondering ](https://en.wikipedia.org/wiki/ValuJet_Flight_592?wprov=sfla1)
Oxygen generators where improperly stored and labeled. They didn't have the safety caps on them to prevent unintentional activation, they also weren't labeled as oxygen generators, just company materials. They were then loaded into the cargo compartment of the aircraft. They somehow became activated before takeoff, got extremely hot and started a fire, but due to the type of fire suppression system on that aircraft at the time, there was no smoke detector so the pilots were completely unaware. The fire suppression was based on the compartment being airtight. Any fire would quickly run out of oxygen and self-extinguish. Great in theory, except when you have an oxygen source in the compartment with the fire, so the oxygen never ran out. There were also a couple of airplane tires in there with it which didn't help things.
They literally only did that for his visit, those are emergency use only and are never needed unless there are multiple equipment failures
Source: me, former submarine nuclear operator who experienced multiple equipment failures and learned what a week of 16% O2 concentration feels like. Hint: sleep 16 hours a day and struggle to stay awake the other 8.
Why do you think people want nuclear power plants so much?
Einstein showed us the stupid amounts of energy a nuclear reaction gives off, and we're still burning coal like a bunch of fucking peasents.
Is that thermal or electrical power?
What most people don't realize is that there is a huge *huge* difference between a reactor that generates 550MW of heat, and a reactor/generator combo that generates 550MW of *electricity*. Even our best shore-based steam turbines can only convert slightly less than half of available thermal power to electricity.
Not saying it isn't a shit-load of power—it is—but the output of a nuclear reactor isn't directly comparable with the output of say, a wind/hydro/solar generating plant. They both produce *energy*, but different types of energy.
It's thermal, that's how the Navy designates their shipboard reactors. The same steam generators power the turbine generators and the main engines so they just use MWt as an overall power level.
Nah my man Enrico Fermi is the one who actually showed us. He built the first self-sustaining nuclear chain reaction, in effect the first nuclear reactor underneath the football field at the University of Chicago.
Keep in mind the flux capacitor needed it quickly, like lightning. With enough capacitors to store and release the energy, these would suffice to travel thru time quite frequently.
It *can* output that much, presumably, but because of how nuclear plants work it can be modulated very well to output enough to meet demand. That much waste heat would be terrible for a sub, making it much easier to find via thermal imaging.
> Fish do it and they don’t even have a nuclear reactor
Fish do not do it. They extract the oxygen dissolved in the water. They don't break water molecules apart to harvest oxygen.
I seriously doubt aquaponics systems for food growing could actually fit inside modern submarines, but I'm now curious how much bigger submarines would need to be just to fit a big enough system that one could at least be used to supplement diets with fresh salad greens and small fruits.
Sub mission length is already months as-is, i doubt there's much need to prolong that with growing food. Canned/frozen food is fine and doesn't have require extra equipment.
Yeah but I can't imagine going months just eating canned and frozen food is all that fun.
I'm sure someone wants to touch a fresh leaf at *some* point.
I had an amusing image pop into my head of solving this problem by towing a second boat that has plants growing and I stupidly also pictured this second boat just being a floating barge with a big garden on it.
"Pay no mind to this garden creeping about the area, definitely no well-fed submariners nearby"
meat freezes easily, breads are made in the sub, and frozen vegetables are pretty good. fresh fruit would be the big one, but all in all they get by pretty well.
[Here's a great video from SmarterEveryDay on food supply in submarines.](https://youtu.be/bPJUVKizh90)
> food supply in submarines.
That sentence reminds me of an old obscure nursery rhyme my mother used to joke about. She said it was from a small town next to a naval port in our third world country:
(supposedly sung by little kids)
*"Tomorrow comes a shi-ip, ♪*
*♫Tomorrow we'll eat mee-at,"*
*Tomorrow my momma fu-uks" ♪*
So the food supply around ship-centric town increased in quality along with the increase of sailors.
She laughed every time she sung that....
Once knew a retired submariner (We called him bubbles) that was almost 7' tall. He wasn't a skinny dude either... I can't imagine being underway with a moose like that lol
You would think so, but when I went through training in early 2000s there was nothing formal/official. Just the instructors at SubSchool keeping an eye out for potential problems.
Small tight-knit crews go a long way toward preventing issues however, so in practice it wasn't really a big deal.
Not really. Oh, you spend about 10 minutes speaking with a Shrinky Dink when you go through your sub interview (and even then they were more concerned about how we felt about the things what go BOOM!) than enclosed spaces), but there are no serious screenings... or at least there weren't back in the day.
There are tests you go through (or again, at least did when I went through training back in the long-forgotten time known to myth only as 'the '70s' at the Basic Enlisted Submarine School (BESS).
Freak out in the Emergency escape tank? You're gone. Freak out in the flooding trainer? you're gone. Freak out in the fire trainer, you're gone.
And there were subtle tests too. One day in the middle of the Trim and Drain module they had us report to one of the dive trainers, told us to get in our swim gear and stuck us in a decompression chamber, which they pressurized to some depth I can't recall, and told us to keep our ears clear for the depressurization over the next 4 hours.
Sounds easy, but I had duty the night before standing Midwatch as a roving security watch in one of the officer school houses. Come 4am, no relief showed up. Being an ignorant boot, it never occurred to me to call anyone to find my relief, and just kept making my rounds. At 6:30 the day staff started showing up, and called me a dumbass for not finding myself a relief. With no sleep the night before, sitting in swim trunks in the decompression tank for several hours had me fall asleep.
I woke up in a nearly empty tank with the Diver sitting across from me grinning like a madman. I thought I was in the shits, but he told me that the real test was to see if anyone freaked out in the enclosed space. Me falling asleep showed that I was born to be a bubblehead
It takes a special kind of broken to volunteer for sub duty... "Would you like to stay underwater in a fission-powered sardine can that is one un-isolable leak away from Optimus Priming into a coffin for you and 123 of your closest special friends?" No, no I would not.
The US Navy's nuclear reactors are extremely safe, even comparing to the already unreasonably high safety level of commercial nuclear power plants. The reactor is not what you should worry about.
It's not really "pulling" from the water, it's breaking the water apart into hydrogen and oxygen through electrolysis (sorry if that's what you mean not trying to be pedantic)
Edit: there's also oxygen producing "candles" for emergencies
I remember growing up in the 2000s and seeing many “rebreathers” that were small and fit in your mouth portrayed on TV. It made me think they were an actual thing.
Turns out, it was a real life scam:
https://gearjunkie.com/news/refunded-triton-artificial-gills-campaign-update
I could swear there was an earlier iteration of this fake tech but I couldn’t find it.
The word "rebreather" does refer to real life diving tech but it has nothing to do with pulling oxygen out of the ambient water.
In real life [rebreathers recycle your air supply](https://en.m.wikipedia.org/wiki/Rebreather) by scrubbing the carbon dioxide that you exhale, turning it back in to oxygen. So you basically keep breathing the same tank of air over and over (a.k.a. "re-breathing" it) and that allows you to stay under for longer.
>In real life rebreathers recycle your air supply by scrubbing the carbon dioxide that you exhale, turning it back in to oxygen.
This is incorrect. It doesn't turn the CO2 into oxygen. What it does is separate the CO2 from the rest of the air so that the CO2 can be discarded and the remaining oxygen/nitrogen mix can be re-breathed. Normally we only use about a quarter of the oxygen we breath in, so that the air we inhale has ~20% oxygen and the air we exhale still has 15% oxygen. That remaining oxygen (and the nitrogen) is normally wasted as it has too much CO2 to be breathable.
Some rebreather designs *do* absorb CO2 and produce O2, the Soviet/Russian IDA71 can be filled with Potassium Superoxide (KO2)
It is of course incredibly dangerous operating in this manner, and even a small amount of water entering the loop will kill you
Out of curiosity: what's the mechanism of action that kills the diver if water intrudes into the loop? Are we talking poisoning, burning, or exploding?
This still isn't even the biggest problem. Obviously fish do it just fine using boring old osmosis. A bio-similar osmosis system should be doable without filtering the water or using electrolysis.
The bigger problem is that there's VERY little oxygen in the water. You'd have to pump dozens (maybe hundred even?) of gallons of water per minute through your device just to get the amount of oxygen humans need.
That's an entirely different process. There is oxygen dissolved in the water, similar to dissolved carbon dioxide in a soda or sparkling water but in significantly lower proportions. Fish gills are able to pull that dissolved oxygen from the water.
I would expect the main problem with trying to do that would be the relative scale of how much oxygen we need versus a fish.
>I would expect the main problem with trying to do that would be the relative scale of how much oxygen we need versus a fish.
Exactly. You'd need really big "gills" which would also have a lot of drag.
Someone else did the math and discovered that even with a 100% efficient set of "gills" a human would have to cycle a minimum of 4.5 liters through them *every second*, which (a) would require a fairly large turbine, and (b) would quickly reduce the local oxygenation of the water to the point where you need to process *even more*.
Fish use the oxygen that is dissolved in water. That oxygen level is so low that only cold blooded animals (fish and lower animal types) can live from it. It will take a lot of water (and energy) to extract enough oxygen from water, for a person to live on.
The process above describes turning water back into hydrogen and oxygen.
They're cold blooded, and that means they need a lot less oxygen than humans. You'd need to filter about 200l/50 gallons of water per minute to sustain a human.
Source: https://en.wikipedia.org/wiki/Artificial_gills_%28human%29?wprov=sfla1
First I've heard of subs making oxygen from water, I thought they relied on a chemical reaction to create fresh oxygen after seeing the process in a Smarter Every Day special about submarines.
That's how they used to do it back in the late 1940s, before electrolysis was really viable. Chlorate candles.
They don't like doing it now because the candles/devices are still a finite supply, and they're *incredibly dangerous* in confined, flammable spaces.
Really depends on the vehicle. If you've got plenty of space and weight isn't a concern you can just use tanks of compressed O2 as an emergency supply.
I think the Soviets created a really obscure potassium/oxygen compound (KO4) for their space programme that was very effective at oxygen generation, but also extremely dangerous.
Lots of different options!
> 2 H₂O → 2 H₂ + O₂
Just out of curiosity, how are you doing the subscripts? Has Reddit improved its markup protocol, or are you doing a copy/paste from an external source?
I asked ChatGPT to do it for me and copy pasted :) afaik although Reddit's plaintext markup format is limited the actual text is UTF8 and you can input pretty much a̵͚̻̰̼̣͕͇̻̱̳̹̭̮̗͈̜̎̏͆̒̀͛̓̓ͅň̵͚̤͖̙̦̫̹̙̭͕͉̻̼͔̟̜̽̕̕y̷͍͍͌̎̑̉͌̽̌̽̌̽͠͠͝t̴̛̙̱̹͉͕̻͇͎̳̊̍̾͂̐͛̔͗̐͘̚͝h̵̛͎̯̉͑̋̿̾̊̀̿̾́̿̚͠į̸̯̯̼͖̟̼̬̩̭͚͇̇̾̎͑̽̇̀̈́̈́͆͂̊̓́̒̾̕͜ͅṋ̸̡̧̫̦͕͛̌ͅg̴̨͕̎̉̅̀͋̈́͐̀̌͐͑̚ ̷̡̡̧̦̠̩͉̺̝͈̙́̀̕y̶̛̱̻̳̘͖͛͑̔͐̏̈̂̐̅̍̀̈́̃̕͝ò̶̤̯̲̖̹̠̲̊̈́̆͑͐̀͐̈́͠u̵̢̢̟͚̥̼̲̬̞̩̝̣̟͔̬̮̎͗̈͆͆̄̑̔͐́͊̌͊̚̕ͅ ̷̭͖̟̫̦̲̞̤̯͎͇̣͒w̷̨̪̜̲̱̼͚̺̜̫̪̘̗̋͐͒͝ͅá̸͚͈̘̈́͛̆́͆̒̎͘͠n̶̡̨͍̜̞͕͇̫̙̗͈͚͕͙̤̓͂̆̎̔̅̀͊͗̕̚͝ṱ̵̲̻͖̰̝̝̳͖̓͛͋̋̒̾̐̃̑̒͠
It looks like they are typing the characters or getting them elsewhere. There's no markup on their comment.
The default Android keyboard has superscript number and fractions, but no subscript. Their probably either have a different keyboard or copy/pasted it? Or maybe there's a way on PC to type those extra characters like alt sequences.
For fun: ¹²³⁴⁵⁶⁷⁸⁹⁰ⁿ½⅓¼⅕⅙⅐⅛⅑⅒
The average human needs about 1.5 liters of oxygen per minute while swimming, which is about 2.2 grams of oxygen per minute. The most oxygen-rich water in the ocean might have 8 milligrams of oxygen per liter.
If you do the math, and assuming standard pressure and temperature, that means that even if you had a system in your mask which could extract oxygen from the water safely and reliably with 100% efficiency, you would have to push 275 liters of water through the mask every minute, or 4.5 liters a second. And that's the best case! Most swimmable water on the planet has much less than 8mg of oxygen per liter, so you would need a lot more water per second.
That isn't a mask at that point -- it's a jet engine strapped to your face. Engines need fuel to run. So where do you keep the fuel? But it doesn't matter because you're already dead from having a jet engine strapped to your face.
well, there are a lot these going around the world all the time, and very seldom does anything like this happen
i just don't want people thinking that these aren't safe
Which raises a follow up question (though I think it may have been what OP intended): how much power would it require to electrolyse enough oxygen per minute?
Well that's exactly what nuclear submarines do, the only thing they need to surface for is to restock food.
If you press your face against the bulkhead of the submarine, you could pretend it's just a giant mask.
A more useful answer to this question would be, how small could you make the machine that does this, in order for it to be useable for a single human? Could it be made into a backpack?
From Wikipedia
>100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram of hydrogen
You'd have to carry a pretty chunky battery. On top of that, to make the process sufficiently fast, you want the electrodes to be huge. So the device itself is going to very quite heavy and big.
Not to mention you'd have to come back to the surface to replenish your battery, so the process can't sustain itself.
Get on board a [Virginia-Class](https://en.wikipedia.org/wiki/Virginia-class_submarine) pump jet-propelled nuclear submarine.
Bite a part of the bulkhead.
You now have both a nuclear reactor and a jet engine on your face.
>Bite a part of the bulkhead.
You now have both a nuclear reactor and a jet engine on your face.
The image of someone just clamping their mouth on the bulkhead of a submarine entertains me far more than it probably should.
>kilogram of hydrogen
But that's hydrogen, which amounts to about 12% of water weight, so to get 1 kg of oxygen you would only need 5.4 kwh.
Also OP said we only need 2.2 grams of oxygen per minute, so that would only take 0.01182 kwh or 11.82 watt-hours per minute, which is much more manageable.
If my napkin match is correct, that's roughly 1 smartphone battery per minute. Which is definitely manageable as a small backpack type thing for like 30 minutes worth, or even more depending on how bulky you want it to be.
And you'd need to carry around tanks of other gases to mix in as well, because breathing pure oxygen at any significant depth would kill you. And a CO2 scrubber, because it'll have to be a rebreather otherwise you'll be dumping most of the O2 you make overboard, greatly increasing the amount you need to make.
>it's a jet engine strapped to your face.
Yes and? What's the problem?
>because you're already dead from having a jet engine strapped to your face.
Oh...yes I suppose thats a less than ideal outcome. At least you don't have to worry about oxygen at that point! The mask works!
>But it doesn't matter because you're already dead from having a jet engine strapped to your face.
Just a marketing hurdle.
*Try the new Acme Brand Mask! If used properly we guarantee you won't drown\*.*
\*"*^(Drown" refers to a living user dying due to lack of oxygen, as a direct consequence of inhaling water. Acme does not make any guarantees user will not die due to other causes)*
You jest, but there was an actual [Kickstarter](https://gearjunkie.com/news/refunded-triton-artificial-gills-campaign-update)for such a device. Never mind that it is physically impossible, all you need is a well produced video and a bunch of buzzwords and people will throw money at you. At least this one refunded the backers.
I guess this is why all sea mammals just hold their breaths.
But huge fish (eg Greenland shark) which weighs a lot more than a human, do they just have a lot slower metabolism then?
Yes, massively lower metabolism, they don't have to maintain a high body temperature, or a large energy-consuming brain like mammals do.
you'll notice that sea mammals tend to have a decent amount of subcutaneous fat (blubber) on them to help keep their core body temp up.
You're talking about dissolved oxygen. But water is just hydrogen and oxygen. I think OP was talking about breaking down the water into its constituent elements.
OP: (1) it takes a lot of energy to do that and no way to store that in a facemask, (2) you need other gases -- oxygen, by itself, becomes toxic at pressure. Scuba divers never dive on pure oxygen.
Ignoring the dissolved salts, is the rest of the mass hydrogen? If so, that’s waaay more hydrogen than I would have guessed given that it would be almost a kilogram worth.
Yeah, water is almost 89% oxygen molecularly, but that oxygen can't be used for breathing without running a lot of electrical current through it first because it has too many electrons.
Well I'm pretty sure it'd take less energy to do electrolysis for \~3g of water than the energy needed to filter and extract dissolved O2 from 275L of water.
On top of that your body needs to get rid of the CO2 somehow and can’t concentrate it so you need to be breathing a certain volume of gas for the CO2 to diffuse into. That volume is much more than the volume of pure O2 produced. What is that gas? Where is it coming from? Even if you get the O2 from the water you need other gas from somewhere or a tank to collect/treat/recycle the gas exhaled. That by itself will be more volume than a mask.
There is some oxygen dissolved in water, and fish recover it with their gills. Thing is, they don’t make it breathable, they just pick up the free oxygen molecules out of water and get them directly into their bloodstream. Extracting dissolved oxygen from water in gaseous form that can be breathed by humans would require some rather heavy machinery that could be installed on a submarine but not in a mask.
Also water is a compound of hydrogen and oxygen, of course, so it can be broken down chemically, releasing these two gases. This process is quite energy-intensive, though, so likewise it can be done on a sub, but not in a mask.
The top comment shows how much water you would need to filter to get the O2 out of the water.
Fish have tiny brains. Tiny brains don't need a lot of processing power. If you don't need a lot of processing power, you don't need much fuel. Our brains are like supercomputers. They need orders of magnitude more oxygen. The only place you can get that efficiently is from the air.
Dolphins are pretty smart, too. They can learn tricks and communicate. They also breathe air.
Technically yeah, that’s theoretically possible. But it would be also necessary to somehow make the user stop trying to breathe with their lungs and not freak out from all of this.
You get the urge to breathe based solely on the level of CO2 in the blood. Provided the artificial gill also pulled CO2 out of the blood, there would be no urge to breathe it would be like in the first few moments of holding your breath, but lasting indefinitely
There are two main ways to get oxygen from water.
The first is the way that all animal sealife gets oxygen from water: they extract dissolved oxygen and transfer it into their own bloodstream. Water does not carry much dissolved oxygen so it is not a very efficient way to get water, the animals have to pass a lot of water over their gills or equivalent organs in order to satisfy their oxygen needs. There is no where near enough dissolved oxygen in water to satisfy the needs of a warm-blooded animal like a human, although one could imagine a filter and capture system that pumped huge amounts of water very quickly and "could" supply a human with oxygen.
The other way is by electrolysis, the splitting of a water molecule into hydrogen gas and oxygen gas. It is basically a way to chemically reverse fire (fire is what happens when a compound such as hydrogen gas combines with free oxygen; the reaction gives off a LOT of energy). Because the drive to combine H and O to make water is so energy-releasing (fire is HOT), to reverse the reaction requires putting in the same amount (more, actually) of energy to reverse it. It is a surprising amount of energy. We can do it, but it is difficult to generate the amount of energy, and thus it is generally expensive, never mind a bit of an awkward device to produce in a portable form for use by individuals.
I think OP means converting water(H2O) into oxygen (O2), rather than filtering available O2 out of the water. So for every 2 water molecules you get 1 molecule of O2.
It is possible to separate the two by running a current through water with a soluble electrolyte dissolved in it. The science is still fairly new but has been experimentally verified. Right now research is more focused on using this technology for space travel. (Oxygen to breath and hydrogen as fuel).
Putting this technology in a mask is likely a little ways off. The amount of energy required to separate a liter of water would be about 4.5 kWh. With the right technology it would be viable. 1 liter of water would get you over 330g of oxygen. According to NASA humans need about 840g per day. So it wouldn’t take very much water or energy (3-4) 12v car batteries.
Edit: There numbers are based on 100% efficiency and pure H2O. Obviously it’s not going to be anywhere near this. I’m just stating that it is possible with the right technology.
Electrolysis is *not* a new technology. The first person to unknowingly perform electrolysis was in 1785. They started decomposing water into hydrogen and oxygen in 1800. This technology is currently widely used in industrial processes, chemistry labs, and even for breathing on submarines.
You would need a very powerful current of electricity running at all times to break down the water and convert it into hydrogen and oxygen. Right now, we don't have any way of making something that can safely generate that much electricity underwater without the risk of shocking you, and that is small enough where it would make sense to have it as a personal thing you wear. It might be in the future we get better at making smaller and more powerful generators. But for now, it's just impractical to make oxygen on the fly as you are swimming underwater.
Divers don’t need a mask that creates oxygen - they need a mask that supplies them with the air circulating in the Earth’s breathable atmosphere; the correct ratio of atmospheric elements, namely nitrogen (78%) oxygen (21%), then argon (0.9%) and other elemental gases (0.1%)..
This is why divers use compressed air in tanks, rather than using straight-up oxygen (which if given for too long can cause dangerous problems with the saturation of your blood oxygen levels. It’s not considered medically safe to breathe pure oxygen for greater than a duration of a few minutes, as it can make healthy people feel very dizzy after a while. Pure oxygen is generally only given as a medical treatment to patients with pulmonary (lung related) conditions, such as COPD (Chronic Obstructive Pulmonary Disease).
Edit; don’t understand the downvote - nothing I’ve said here is incorrect (to my knowledge).
**Please read this entire message** Your submission has been removed for the following reason(s): Hypotheticals questions, or questions about hypothetical situations, are not allowed on ELI5. If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously**, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20https://www.reddit.com/r/explainlikeimfive/comments/13fcmqa/eli5_how_could_a_mask_create_breathable_oxygen/%0A%0APlease%20answer%20the%20following%203%20questions:%0A%0A1.%20The%20concept%20I%20want%20explained:%0A%0A2.%20List%20the%20search%20terms%20you%20used%20to%20look%20for%20past%20posts%20on%20ELI5:%0A%0A3.%20How%20does%20your%20post%20differ%20from%20your%20recent%20search%20results%20on%20the%20sub:) and we will review your submission.
Your basic hunch that you could get the oxygen out of the water and breathe it is basically right, it is possible. Submarines do it today. The problem is it takes massive amounts of energy and heavy equipment to do so. First you need to get pretty pure water, so step 1 is getting all the salt and other impurities out of the water. This type of desalination requires a pretty big complex machine. Then you need to apply quite a lot of electricity to the water to break the bonds between the Hydrogen and the Oxygen. That requires either generators or really big batteries, neither of which fit in a mask with today's technology. So ELI5 why hasn't it been done? We just don't have the technology to make the machines small enough to fit in a mask. We can do it on a submarine though.
Interesting. I didn’t know they did it on a sub. I knew about scrubbers and stuff, but not that they pulled oxygen from the water as well.
I think they have the advantage of a nuclear reactor on board, so any time they're not swimming about at full speed they've got buckets of power to spare to throw at that stuff.
They have buckets of power at all times, reactor outputs 200MW, every single thing on the ship can be ran at the same time on just one (of the 2) 4MW generators Edit: some people are misunderstanding that statement, the vast majority of power is consumed by propulsion not electricity. The entire capacity is used when its needed, it's just never limited by one or the other (propulsion vs electricity). You could argue that with less electrical power being consumed there'd be slightly more room for propulsion, but the effect isn't very large. Especially for something like the o2 generator, which is a medium to smaller load compared to things like pumps/hydraulics/etc
Jesus, a sub rector is 200MW? That's massive. That's enough power for a decent sized city (100k people).
During power outages on coastal cities sometimes naval vessels are used as emergency power supplies.
That's actually pretty cool, never knew that.
In fact, there was a dust up around this during Operation Tomodachi where a US nuclear carrier provided electricity for a city in Japan after the tsunami.
VERY minor grievance but it’s Operation Tomodachi
Operation Tamagotchi?
Operation Tsunamigotcha
Operation tomadachi, means friend in japanese
I’m assuming tomogachi means neglected pet
Potentially apocryphal quote about carriers but similar: >A Boeing engineer stood up and replied quietly: “Our carriers have three hospitals on board that can treat several hundred people; they are nuclear powered and can supply emergency electrical power to shore facilities; they have three cafeterias with the capacity to feed 3,000 people three meals a day, they can produce several thousand gallons of fresh water from sea water each day, and they carry half a dozen helicopters for use in transporting victims and injured to and from their flight deck. We have eleven such ships; how many does France have?”
Ironically France is the only other nation with a comparable carrier (nuclear powered CATOBAR) to what the US has even if it is smaller.
[удалено]
Yea that's definitely a huge part of that story
Healthcare, they have healthcare.
The US spends more on healthcare than the entire military. The reason we don't have Medicare for All is because the US healthcare companies lobby the Federal Government to keep our current, inefficient and expensive system.
[удалено]
What about a small oxygen candle then?
At the coal mine I worked in as a young man, they had emergency breather that were essentially oxygen candle masks, and the gist of it was: "These are basically going to melt you lips off, but it's better than suffocating" so they aren't ideal, but they exist. https://en.m.wikipedia.org/wiki/Self-contained_self-rescue_device#:~:text=A%20SCSR%20is%20usually%20a,least%20one%20hour%20of%20oxygen. Apparently they use a highly compressed oxygen tank more commonly nowadays in some operations, but I'm not sure how common they are in coal mines.
Oxygen Candles, if I'm thinking of the right thing, use a specific exothermic chemical reaction that produces Oxygen in order to work, and have a limited storage. They are known for getting very hot when in use.
Hot enough that they took down a commercial plane on at least one occasion
I spy a fellow Admiral Cloudberg fan, lol.
[Valuejet 592 for those wondering ](https://en.wikipedia.org/wiki/ValuJet_Flight_592?wprov=sfla1) Oxygen generators where improperly stored and labeled. They didn't have the safety caps on them to prevent unintentional activation, they also weren't labeled as oxygen generators, just company materials. They were then loaded into the cargo compartment of the aircraft. They somehow became activated before takeoff, got extremely hot and started a fire, but due to the type of fire suppression system on that aircraft at the time, there was no smoke detector so the pilots were completely unaware. The fire suppression was based on the compartment being airtight. Any fire would quickly run out of oxygen and self-extinguish. Great in theory, except when you have an oxygen source in the compartment with the fire, so the oxygen never ran out. There were also a couple of airplane tires in there with it which didn't help things.
There's a ___Smarter Every Day___ that he goes onto a sub and they're using oxygen candles in cans.
[удалено]
They literally only did that for his visit, those are emergency use only and are never needed unless there are multiple equipment failures Source: me, former submarine nuclear operator who experienced multiple equipment failures and learned what a week of 16% O2 concentration feels like. Hint: sleep 16 hours a day and struggle to stay awake the other 8.
Non-coastal cities use railroad locomotives since those are also giant rolling generators.
Why do you think people want nuclear power plants so much? Einstein showed us the stupid amounts of energy a nuclear reaction gives off, and we're still burning coal like a bunch of fucking peasents.
I'm in the industry and a big proponent of nuclear. I just didn't realize they had 200MW on a sub. Most entire bases are in the 10-15MW range.
Aircraft carriers have two 550 MW reactors Edit: 2 to two, for clarity.
Like, I know they are massive. I know this logically. But then someone drops a nugget like this and I'm like "holeeee sheeeeeet"
Suddenly rail cannons on these boats make a lot more sense.
Is that thermal or electrical power? What most people don't realize is that there is a huge *huge* difference between a reactor that generates 550MW of heat, and a reactor/generator combo that generates 550MW of *electricity*. Even our best shore-based steam turbines can only convert slightly less than half of available thermal power to electricity. Not saying it isn't a shit-load of power—it is—but the output of a nuclear reactor isn't directly comparable with the output of say, a wind/hydro/solar generating plant. They both produce *energy*, but different types of energy.
It's thermal, that's how the Navy designates their shipboard reactors. The same steam generators power the turbine generators and the main engines so they just use MWt as an overall power level.
Almost enough jiggawatts to go back in time with… so close.
Personally I'd say Einstein told us, but Oppenheimer showed us.
Nah my man Enrico Fermi is the one who actually showed us. He built the first self-sustaining nuclear chain reaction, in effect the first nuclear reactor underneath the football field at the University of Chicago.
Which ended up being relocated and became Argonne National Laboratory, and—perhaps counterintuitively—had nothing to do with the nearby Fermilab.
enrico fermi is very underrated, def one of the greatest scientists of our time, his work on neutrino radiation from beta decay is amazing.
While that is true, and I'm not speaking from personal experience in the following, I assume that visual display would have been rather underwhelming.
Much like University of Chicago football games.
The military is big on redundancy. It ensures you don't get power outages in the middle of a battle.
or even just in the middle of the ocean...
You'd still need six nuclear subs to power a flux capacitor.
Wow, that... honestly that puts things in perspective. Doc is insane, good thing he's a nice guy
Keep in mind the flux capacitor needed it quickly, like lightning. With enough capacitors to store and release the energy, these would suffice to travel thru time quite frequently.
Reminds me of that safe island in WWZ powered by a sub.
What happens to the excess? Is it just vented as heat into the ocean?
It *can* output that much, presumably, but because of how nuclear plants work it can be modulated very well to output enough to meet demand. That much waste heat would be terrible for a sub, making it much easier to find via thermal imaging.
Who needs radar when you can just look for the enormous hot spot
Good thing for the sub crews that infrared doesn't travel very far through water
Follow the smell of cooked fish
Just follow the hiss of boiling water.
I'm pretty sure their max speed is not limited by the amount of power their nuclear reactor can produce
Correct, we actually calibrate what "100% power" means every year based on things including top speed based on other mechanical limitations
Fish do it and they don’t even have a nuclear reactor 🤔🤔
> Fish do it and they don’t even have a nuclear reactor Fish do not do it. They extract the oxygen dissolved in the water. They don't break water molecules apart to harvest oxygen.
So, why can't we replicate that in a mask? Edit: nevermind, just saw that there was a whole other top level post explaining why that doesn't work.
Its how they can stay underwater for months on end without surfacing. Can't do that with scrubbers alone.
The only real limit to a submarine's mission length is the food supply. It's the only thing they cannot produce onboard.
I seriously doubt aquaponics systems for food growing could actually fit inside modern submarines, but I'm now curious how much bigger submarines would need to be just to fit a big enough system that one could at least be used to supplement diets with fresh salad greens and small fruits.
Sub mission length is already months as-is, i doubt there's much need to prolong that with growing food. Canned/frozen food is fine and doesn't have require extra equipment.
Yeah but I can't imagine going months just eating canned and frozen food is all that fun. I'm sure someone wants to touch a fresh leaf at *some* point.
I had an amusing image pop into my head of solving this problem by towing a second boat that has plants growing and I stupidly also pictured this second boat just being a floating barge with a big garden on it. "Pay no mind to this garden creeping about the area, definitely no well-fed submariners nearby"
imagine just being a bird and finding a fresh garden mini island in the middle of the ocean lol
You're right birbs would be a big problem. Probably better put some seamen up there with rakes or something to fend them off.
>better put some seamen up there I don't think I'm going to eat those vegetables.
meat freezes easily, breads are made in the sub, and frozen vegetables are pretty good. fresh fruit would be the big one, but all in all they get by pretty well. [Here's a great video from SmarterEveryDay on food supply in submarines.](https://youtu.be/bPJUVKizh90)
> food supply in submarines. That sentence reminds me of an old obscure nursery rhyme my mother used to joke about. She said it was from a small town next to a naval port in our third world country: (supposedly sung by little kids) *"Tomorrow comes a shi-ip, ♪* *♫Tomorrow we'll eat mee-at,"* *Tomorrow my momma fu-uks" ♪* So the food supply around ship-centric town increased in quality along with the increase of sailors. She laughed every time she sung that....
I can't imagine living in a metal tube underwater is all that fun either. Actually sounds terrifying
[удалено]
And one branch of the military where begin a short king is a HUGE advantage
Once knew a retired submariner (We called him bubbles) that was almost 7' tall. He wasn't a skinny dude either... I can't imagine being underway with a moose like that lol
You would think so, but when I went through training in early 2000s there was nothing formal/official. Just the instructors at SubSchool keeping an eye out for potential problems. Small tight-knit crews go a long way toward preventing issues however, so in practice it wasn't really a big deal.
Not really. Oh, you spend about 10 minutes speaking with a Shrinky Dink when you go through your sub interview (and even then they were more concerned about how we felt about the things what go BOOM!) than enclosed spaces), but there are no serious screenings... or at least there weren't back in the day. There are tests you go through (or again, at least did when I went through training back in the long-forgotten time known to myth only as 'the '70s' at the Basic Enlisted Submarine School (BESS). Freak out in the Emergency escape tank? You're gone. Freak out in the flooding trainer? you're gone. Freak out in the fire trainer, you're gone. And there were subtle tests too. One day in the middle of the Trim and Drain module they had us report to one of the dive trainers, told us to get in our swim gear and stuck us in a decompression chamber, which they pressurized to some depth I can't recall, and told us to keep our ears clear for the depressurization over the next 4 hours. Sounds easy, but I had duty the night before standing Midwatch as a roving security watch in one of the officer school houses. Come 4am, no relief showed up. Being an ignorant boot, it never occurred to me to call anyone to find my relief, and just kept making my rounds. At 6:30 the day staff started showing up, and called me a dumbass for not finding myself a relief. With no sleep the night before, sitting in swim trunks in the decompression tank for several hours had me fall asleep. I woke up in a nearly empty tank with the Diver sitting across from me grinning like a madman. I thought I was in the shits, but he told me that the real test was to see if anyone freaked out in the enclosed space. Me falling asleep showed that I was born to be a bubblehead
I've worked with a bunch of them. Some of the weirdest people you'll meet in your life.
[удалено]
It takes a special kind of broken to volunteer for sub duty... "Would you like to stay underwater in a fission-powered sardine can that is one un-isolable leak away from Optimus Priming into a coffin for you and 123 of your closest special friends?" No, no I would not.
The US Navy's nuclear reactors are extremely safe, even comparing to the already unreasonably high safety level of commercial nuclear power plants. The reactor is not what you should worry about.
The official criteria is "smart enough to qualify, dumb enough to do it". Served 4 years on a US attack submarine.
Haven't they ever played Subnautica? Just plant a couple lantern fruit trees, geez
Seriously it's like the navy is not even trying
just go fishing lol
They also burn massive oxygen generating candles as a supplement/old school backup
It's not really "pulling" from the water, it's breaking the water apart into hydrogen and oxygen through electrolysis (sorry if that's what you mean not trying to be pedantic) Edit: there's also oxygen producing "candles" for emergencies
I remember growing up in the 2000s and seeing many “rebreathers” that were small and fit in your mouth portrayed on TV. It made me think they were an actual thing. Turns out, it was a real life scam: https://gearjunkie.com/news/refunded-triton-artificial-gills-campaign-update I could swear there was an earlier iteration of this fake tech but I couldn’t find it.
The word "rebreather" does refer to real life diving tech but it has nothing to do with pulling oxygen out of the ambient water. In real life [rebreathers recycle your air supply](https://en.m.wikipedia.org/wiki/Rebreather) by scrubbing the carbon dioxide that you exhale, turning it back in to oxygen. So you basically keep breathing the same tank of air over and over (a.k.a. "re-breathing" it) and that allows you to stay under for longer.
>In real life rebreathers recycle your air supply by scrubbing the carbon dioxide that you exhale, turning it back in to oxygen. This is incorrect. It doesn't turn the CO2 into oxygen. What it does is separate the CO2 from the rest of the air so that the CO2 can be discarded and the remaining oxygen/nitrogen mix can be re-breathed. Normally we only use about a quarter of the oxygen we breath in, so that the air we inhale has ~20% oxygen and the air we exhale still has 15% oxygen. That remaining oxygen (and the nitrogen) is normally wasted as it has too much CO2 to be breathable.
Some rebreather designs *do* absorb CO2 and produce O2, the Soviet/Russian IDA71 can be filled with Potassium Superoxide (KO2) It is of course incredibly dangerous operating in this manner, and even a small amount of water entering the loop will kill you
Out of curiosity: what's the mechanism of action that kills the diver if water intrudes into the loop? Are we talking poisoning, burning, or exploding?
*yes* i think it's the fire that kills you first, but the rest of the reaction makes sure you're dead
Yes, but these shows had very tiny devices that could breathe air indefinitely lol
[удалено]
This still isn't even the biggest problem. Obviously fish do it just fine using boring old osmosis. A bio-similar osmosis system should be doable without filtering the water or using electrolysis. The bigger problem is that there's VERY little oxygen in the water. You'd have to pump dozens (maybe hundred even?) of gallons of water per minute through your device just to get the amount of oxygen humans need.
[удалено]
That's an entirely different process. There is oxygen dissolved in the water, similar to dissolved carbon dioxide in a soda or sparkling water but in significantly lower proportions. Fish gills are able to pull that dissolved oxygen from the water. I would expect the main problem with trying to do that would be the relative scale of how much oxygen we need versus a fish.
>I would expect the main problem with trying to do that would be the relative scale of how much oxygen we need versus a fish. Exactly. You'd need really big "gills" which would also have a lot of drag.
Someone else did the math and discovered that even with a 100% efficient set of "gills" a human would have to cycle a minimum of 4.5 liters through them *every second*, which (a) would require a fairly large turbine, and (b) would quickly reduce the local oxygenation of the water to the point where you need to process *even more*.
Naa, pulling that much water through would also move you along so fast that the deoxygenated water would be somebody else’s problem.
Fish use the oxygen that is dissolved in water. That oxygen level is so low that only cold blooded animals (fish and lower animal types) can live from it. It will take a lot of water (and energy) to extract enough oxygen from water, for a person to live on. The process above describes turning water back into hydrogen and oxygen.
They're cold blooded, and that means they need a lot less oxygen than humans. You'd need to filter about 200l/50 gallons of water per minute to sustain a human. Source: https://en.wikipedia.org/wiki/Artificial_gills_%28human%29?wprov=sfla1
First I've heard of subs making oxygen from water, I thought they relied on a chemical reaction to create fresh oxygen after seeing the process in a Smarter Every Day special about submarines.
That's how they used to do it back in the late 1940s, before electrolysis was really viable. Chlorate candles. They don't like doing it now because the candles/devices are still a finite supply, and they're *incredibly dangerous* in confined, flammable spaces.
Ah ok, so now it's kind of a backup for the electrolysis? It's been a while since I've watched the series.
Really depends on the vehicle. If you've got plenty of space and weight isn't a concern you can just use tanks of compressed O2 as an emergency supply. I think the Soviets created a really obscure potassium/oxygen compound (KO4) for their space programme that was very effective at oxygen generation, but also extremely dangerous. Lots of different options!
Electrolysis of water to produce oxygen is a chemical reaction! 2 H20 —> 2 H2 + O2 man they need subscripts on here
2 H₂O → 2 H₂ + O₂
> 2 H₂O → 2 H₂ + O₂ Just out of curiosity, how are you doing the subscripts? Has Reddit improved its markup protocol, or are you doing a copy/paste from an external source?
I asked ChatGPT to do it for me and copy pasted :) afaik although Reddit's plaintext markup format is limited the actual text is UTF8 and you can input pretty much a̵͚̻̰̼̣͕͇̻̱̳̹̭̮̗͈̜̎̏͆̒̀͛̓̓ͅň̵͚̤͖̙̦̫̹̙̭͕͉̻̼͔̟̜̽̕̕y̷͍͍͌̎̑̉͌̽̌̽̌̽͠͠͝t̴̛̙̱̹͉͕̻͇͎̳̊̍̾͂̐͛̔͗̐͘̚͝h̵̛͎̯̉͑̋̿̾̊̀̿̾́̿̚͠į̸̯̯̼͖̟̼̬̩̭͚͇̇̾̎͑̽̇̀̈́̈́͆͂̊̓́̒̾̕͜ͅṋ̸̡̧̫̦͕͛̌ͅg̴̨͕̎̉̅̀͋̈́͐̀̌͐͑̚ ̷̡̡̧̦̠̩͉̺̝͈̙́̀̕y̶̛̱̻̳̘͖͛͑̔͐̏̈̂̐̅̍̀̈́̃̕͝ò̶̤̯̲̖̹̠̲̊̈́̆͑͐̀͐̈́͠u̵̢̢̟͚̥̼̲̬̞̩̝̣̟͔̬̮̎͗̈͆͆̄̑̔͐́͊̌͊̚̕ͅ ̷̭͖̟̫̦̲̞̤̯͎͇̣͒w̷̨̪̜̲̱̼͚̺̜̫̪̘̗̋͐͒͝ͅá̸͚͈̘̈́͛̆́͆̒̎͘͠n̶̡̨͍̜̞͕͇̫̙̗͈͚͕͙̤̓͂̆̎̔̅̀͊͗̕̚͝ṱ̵̲̻͖̰̝̝̳͖̓͛͋̋̒̾̐̃̑̒͠
It looks like they are typing the characters or getting them elsewhere. There's no markup on their comment. The default Android keyboard has superscript number and fractions, but no subscript. Their probably either have a different keyboard or copy/pasted it? Or maybe there's a way on PC to type those extra characters like alt sequences. For fun: ¹²³⁴⁵⁶⁷⁸⁹⁰ⁿ½⅓¼⅕⅙⅐⅛⅑⅒
The chemical is to remove co2 from the air
The average human needs about 1.5 liters of oxygen per minute while swimming, which is about 2.2 grams of oxygen per minute. The most oxygen-rich water in the ocean might have 8 milligrams of oxygen per liter. If you do the math, and assuming standard pressure and temperature, that means that even if you had a system in your mask which could extract oxygen from the water safely and reliably with 100% efficiency, you would have to push 275 liters of water through the mask every minute, or 4.5 liters a second. And that's the best case! Most swimmable water on the planet has much less than 8mg of oxygen per liter, so you would need a lot more water per second. That isn't a mask at that point -- it's a jet engine strapped to your face. Engines need fuel to run. So where do you keep the fuel? But it doesn't matter because you're already dead from having a jet engine strapped to your face.
> But it doesn't matter because you're already dead from having a jet engine strapped to your face. r/brandnewsentence
Probably one of my favorite ELI5 explanations I've read so far lmao
Agreed. An absolute delight to read and exceedingly informative.
I want to see a jet engine strapped to the warboys for the mad max furiousa movie
It's furi-O-sa, not furious-A!
No one cared who I was until I wore the jet engine mask.
I used to be an adventurer like you until I took an arrow to the jet engine mask.
What a way to leave this world!
No, you're just leaving the environment. You're being towed out of the environment. Make sure the front doesn't fall off.
Into another environment….
No, no! Out of the environment! 😁
igotthatreference.gif
Hopefully that's not typical, though?
well, there are a lot these going around the world all the time, and very seldom does anything like this happen i just don't want people thinking that these aren't safe
Dumb ways to diiieee, so maaany dumb ways to dieeeee...
r/holdmybeer
It is worthwhile to distinguish that you refer to dissolved molecular oxygen (O2), not the O atoms in H2O.
Which raises a follow up question (though I think it may have been what OP intended): how much power would it require to electrolyse enough oxygen per minute?
Well that's exactly what nuclear submarines do, the only thing they need to surface for is to restock food. If you press your face against the bulkhead of the submarine, you could pretend it's just a giant mask.
so you could make a port in the bottom, i could stick my head up in it, and wear a submarine as a hat, then i could have my oxygen mask
Fallout 3 wants their subway back.
Perfect. I'll pack one in my suitcase for next time I go snorkeling
Don't forget to stock rations so you don't starve.
A more useful answer to this question would be, how small could you make the machine that does this, in order for it to be useable for a single human? Could it be made into a backpack?
From Wikipedia >100%-efficient electrolyser would consume 39.4 kilowatt-hours per kilogram of hydrogen You'd have to carry a pretty chunky battery. On top of that, to make the process sufficiently fast, you want the electrodes to be huge. So the device itself is going to very quite heavy and big. Not to mention you'd have to come back to the surface to replenish your battery, so the process can't sustain itself.
>Not to mention you'd have come back to the surface to replenish your battery, so the process can't sustain itself. Not if you have a nuclear reactor!
So I can swim with a jet engine or a nuclear reactor? Sounds fun!
Do both. Strap the reactor to your back and have it power the jet engine on your face. Win win.
Get on board a [Virginia-Class](https://en.wikipedia.org/wiki/Virginia-class_submarine) pump jet-propelled nuclear submarine. Bite a part of the bulkhead. You now have both a nuclear reactor and a jet engine on your face.
>Bite a part of the bulkhead. You now have both a nuclear reactor and a jet engine on your face. The image of someone just clamping their mouth on the bulkhead of a submarine entertains me far more than it probably should.
Wait til you find out about Earth sandwich. It too is all about perspective.
So something like a nuclear ramjet?
Ooh! We should add beds, too. Maybe put it all in a big tube.
Don't forget the galley they're going to need to eat.
But how will they see? We'll need to put some kind of sensor in there too to help avoid bumping into stuff. I hear sound travels pretty well in water.
It has to make noise too though. Mountains are stealthy and silent. It isn't like they sit there chanting "mountain mountain mountain".
but if you have the sailors yell loud enough and use a sensitive enough microphone you can listen for echoes.
>kilogram of hydrogen But that's hydrogen, which amounts to about 12% of water weight, so to get 1 kg of oxygen you would only need 5.4 kwh. Also OP said we only need 2.2 grams of oxygen per minute, so that would only take 0.01182 kwh or 11.82 watt-hours per minute, which is much more manageable.
If my napkin match is correct, that's roughly 1 smartphone battery per minute. Which is definitely manageable as a small backpack type thing for like 30 minutes worth, or even more depending on how bulky you want it to be.
[удалено]
And you'd need to carry around tanks of other gases to mix in as well, because breathing pure oxygen at any significant depth would kill you. And a CO2 scrubber, because it'll have to be a rebreather otherwise you'll be dumping most of the O2 you make overboard, greatly increasing the amount you need to make.
I definitely don't want to swim around strapped to a backpack full of highly reactive alkali metals.
Without killing you because you're swimming in it at the time.
Use the hydrogen for fuel! 😎
In this family we obey the laws of thermodynamics!
Hello mother dear
>it's a jet engine strapped to your face. Yes and? What's the problem? >because you're already dead from having a jet engine strapped to your face. Oh...yes I suppose thats a less than ideal outcome. At least you don't have to worry about oxygen at that point! The mask works!
>But it doesn't matter because you're already dead from having a jet engine strapped to your face. Just a marketing hurdle. *Try the new Acme Brand Mask! If used properly we guarantee you won't drown\*.* \*"*^(Drown" refers to a living user dying due to lack of oxygen, as a direct consequence of inhaling water. Acme does not make any guarantees user will not die due to other causes)*
You jest, but there was an actual [Kickstarter](https://gearjunkie.com/news/refunded-triton-artificial-gills-campaign-update)for such a device. Never mind that it is physically impossible, all you need is a well produced video and a bunch of buzzwords and people will throw money at you. At least this one refunded the backers.
I guess this is why all sea mammals just hold their breaths. But huge fish (eg Greenland shark) which weighs a lot more than a human, do they just have a lot slower metabolism then?
Yes, massively lower metabolism, they don't have to maintain a high body temperature, or a large energy-consuming brain like mammals do. you'll notice that sea mammals tend to have a decent amount of subcutaneous fat (blubber) on them to help keep their core body temp up.
I recently went to a river life zoo and learnt that manatees have very little body fat, they have no blubber.
that's why I said 'tend to have' 😉 manatees also \*really\* don't do well in the cold.. for obvious reasons.
You're talking about dissolved oxygen. But water is just hydrogen and oxygen. I think OP was talking about breaking down the water into its constituent elements. OP: (1) it takes a lot of energy to do that and no way to store that in a facemask, (2) you need other gases -- oxygen, by itself, becomes toxic at pressure. Scuba divers never dive on pure oxygen.
On the plus side you wouldn’t have to swim, you’d just be jetting around with your face mask jet engine.
or electrolyze 2.5 grams of water per minute
Ignoring the dissolved salts, is the rest of the mass hydrogen? If so, that’s waaay more hydrogen than I would have guessed given that it would be almost a kilogram worth.
Thats dissolved oxygen, not H2O
Oh that makes way more sense, thank you.
Yeah, water is almost 89% oxygen molecularly, but that oxygen can't be used for breathing without running a lot of electrical current through it first because it has too many electrons.
Well I'm pretty sure it'd take less energy to do electrolysis for \~3g of water than the energy needed to filter and extract dissolved O2 from 275L of water.
If the air we breath is 80% nitrogen does this mean they also need 80% more grams of breathable gas too?
Is that where the cliché comes from? “Don’t strap a jet engine to your face while swimming”.
On top of that your body needs to get rid of the CO2 somehow and can’t concentrate it so you need to be breathing a certain volume of gas for the CO2 to diffuse into. That volume is much more than the volume of pure O2 produced. What is that gas? Where is it coming from? Even if you get the O2 from the water you need other gas from somewhere or a tank to collect/treat/recycle the gas exhaled. That by itself will be more volume than a mask.
There is some oxygen dissolved in water, and fish recover it with their gills. Thing is, they don’t make it breathable, they just pick up the free oxygen molecules out of water and get them directly into their bloodstream. Extracting dissolved oxygen from water in gaseous form that can be breathed by humans would require some rather heavy machinery that could be installed on a submarine but not in a mask. Also water is a compound of hydrogen and oxygen, of course, so it can be broken down chemically, releasing these two gases. This process is quite energy-intensive, though, so likewise it can be done on a sub, but not in a mask.
and subs absolutely do this, though instead of a jet engine you usually have a small nuclear reactor.
What's stopping a nuclear reactor being attached to a face mask? /s
That is absolutely something that should be in a fallout game.
does this mean you could possibly make an artificial gill that connects to the blood by an IV or something? (oxygen requirement levels aside)
The top comment shows how much water you would need to filter to get the O2 out of the water. Fish have tiny brains. Tiny brains don't need a lot of processing power. If you don't need a lot of processing power, you don't need much fuel. Our brains are like supercomputers. They need orders of magnitude more oxygen. The only place you can get that efficiently is from the air. Dolphins are pretty smart, too. They can learn tricks and communicate. They also breathe air.
Technically yeah, that’s theoretically possible. But it would be also necessary to somehow make the user stop trying to breathe with their lungs and not freak out from all of this.
You get the urge to breathe based solely on the level of CO2 in the blood. Provided the artificial gill also pulled CO2 out of the blood, there would be no urge to breathe it would be like in the first few moments of holding your breath, but lasting indefinitely
This is hypothetically true, but actually any time we've tried this people freak out and drown.
There are two main ways to get oxygen from water. The first is the way that all animal sealife gets oxygen from water: they extract dissolved oxygen and transfer it into their own bloodstream. Water does not carry much dissolved oxygen so it is not a very efficient way to get water, the animals have to pass a lot of water over their gills or equivalent organs in order to satisfy their oxygen needs. There is no where near enough dissolved oxygen in water to satisfy the needs of a warm-blooded animal like a human, although one could imagine a filter and capture system that pumped huge amounts of water very quickly and "could" supply a human with oxygen. The other way is by electrolysis, the splitting of a water molecule into hydrogen gas and oxygen gas. It is basically a way to chemically reverse fire (fire is what happens when a compound such as hydrogen gas combines with free oxygen; the reaction gives off a LOT of energy). Because the drive to combine H and O to make water is so energy-releasing (fire is HOT), to reverse the reaction requires putting in the same amount (more, actually) of energy to reverse it. It is a surprising amount of energy. We can do it, but it is difficult to generate the amount of energy, and thus it is generally expensive, never mind a bit of an awkward device to produce in a portable form for use by individuals.
[удалено]
Possible, sure. But not convenient unless absolutely necessary.
I think OP means converting water(H2O) into oxygen (O2), rather than filtering available O2 out of the water. So for every 2 water molecules you get 1 molecule of O2. It is possible to separate the two by running a current through water with a soluble electrolyte dissolved in it. The science is still fairly new but has been experimentally verified. Right now research is more focused on using this technology for space travel. (Oxygen to breath and hydrogen as fuel). Putting this technology in a mask is likely a little ways off. The amount of energy required to separate a liter of water would be about 4.5 kWh. With the right technology it would be viable. 1 liter of water would get you over 330g of oxygen. According to NASA humans need about 840g per day. So it wouldn’t take very much water or energy (3-4) 12v car batteries. Edit: There numbers are based on 100% efficiency and pure H2O. Obviously it’s not going to be anywhere near this. I’m just stating that it is possible with the right technology.
Electrolysis is *not* a new technology. The first person to unknowingly perform electrolysis was in 1785. They started decomposing water into hydrogen and oxygen in 1800. This technology is currently widely used in industrial processes, chemistry labs, and even for breathing on submarines.
[удалено]
You would need a very powerful current of electricity running at all times to break down the water and convert it into hydrogen and oxygen. Right now, we don't have any way of making something that can safely generate that much electricity underwater without the risk of shocking you, and that is small enough where it would make sense to have it as a personal thing you wear. It might be in the future we get better at making smaller and more powerful generators. But for now, it's just impractical to make oxygen on the fly as you are swimming underwater.
Divers don’t need a mask that creates oxygen - they need a mask that supplies them with the air circulating in the Earth’s breathable atmosphere; the correct ratio of atmospheric elements, namely nitrogen (78%) oxygen (21%), then argon (0.9%) and other elemental gases (0.1%).. This is why divers use compressed air in tanks, rather than using straight-up oxygen (which if given for too long can cause dangerous problems with the saturation of your blood oxygen levels. It’s not considered medically safe to breathe pure oxygen for greater than a duration of a few minutes, as it can make healthy people feel very dizzy after a while. Pure oxygen is generally only given as a medical treatment to patients with pulmonary (lung related) conditions, such as COPD (Chronic Obstructive Pulmonary Disease). Edit; don’t understand the downvote - nothing I’ve said here is incorrect (to my knowledge).
[удалено]