8 ms·

Surviving under water in an air bubble

196 points by Xcelerate 13y ago

Uchikoma 13y ago
From the comment that explains a lot, but misses the point completely (exchange of oxygen between the bubble and the sea to replenish oxygen in the bubble): Don't ask a chemistry question on a physics board ;-)
- adamtulinius 13y ago
  And in a comment to that comment: "Using imperial measures in a discussion on Physics?" hehe :-)
  - Uchikoma 13y ago
    :-)
inthewind 13y ago
Related: http://www.isracast.com/article.aspx?id=63 http://www.isracast.com/article.aspx?id=63
- fletchowns 13y ago
  Warning: Audio will start playing on this site. Scared the shit out of me!
usaphp 13y ago
A person can survive in an air bubble but after 13 hours he will start having a trench foot condition: http://en.wikipedia.org/wiki/Trench_foot http://en.wikipedia.org/wiki/Trench_foot
- mistercow 13y ago
  According to the article you linked, trench foot occurs in temperatures up to 60°F. The water temperature off the cost of Nigeria this time of year is closer to 80°F, so I'm guessing trench foot wouldn't be a problem.
  - jessaustin 13y ago
    The temperature at a depth of 30m is certainly not 80°F.
jlgreco 13y ago
Does anyone know how survivable rapidly surfacing from 30 meters would be? Wolfram Alpha has the pressure down there at almost 400 kPa (compared to 100 kPa) so my suspicion is "not at all", but I'm not really familiar with the tolerances and life expectancies with the bends. 30 meters is just agonizingly close to the surface though, well within what most adults could do horizontally (particularly if their life depended on it.) Being that close to the surface, but still so far away, must be absolutely awful.
- fletchowns 13y ago
  Probably not very survivable, given that they stuck the guy in a decompression chamber for 60 hours.
  - jlgreco 13y ago
    Well yeah, but even a slight chance would be worth attempting if you were in such a position, even if it were just a 5% chance of survival, compared with the 100% chance they were probably shooting for with the 60 hour decompression. Of course if attempting it meant certain but excruciating death, then taking a shot at it would not be the way to go.
  - ars 13y ago
    They left him in there for so long because he was in the water for so long. (i.e. plenty of time for nitrogen to dissolve). If he had swum up right away he would not need decompression. I imagine in the dark he would have been too scared of not being able to find the way out in the cluttered sunken vessel.
    - jlgreco 13y ago
      He probably also didn't know how close to the surface he was.
- Udo 13y ago
  It depends on how long you've been down there. If you have just been dragged under water with your boat, it's probably safe to make a rapid ascent (don't hold your breath though) - in fact, diving school teaches emergency ascents for situations where no other options apply, even if the diver is in need of decompression. However, after about half an hour it becomes a serious problem that gets worse over time as gases start to infuse into the tissue. If rescue (and access to a pressure chamber) is available right away, I'd make that ascent immediately even after being down there for a longer time. It beats drowning or CO2 poisoning. Dive tables illustrate pretty well how the relationship between depth and time works: http://www.naui.org/tables.aspx http://www.naui.org/tables.aspx
coldarchon 13y ago
No idea why this is on Hacker News, but the question is wrong, he has to ask when the carbon dioxide poisoning happens. Contrary to the presentation of this situation in all movies from Hollywood, it is more likely to die from carbon dioxide poisoning than from "oxygen running out".
Xcelerate 13y ago
D'oh! Just realized I was a chemical engineer an hour after I posted this :) The steps to solve this problem are pretty simple: 1) Find the diffusion coefficient of oxygen in seawater. This can be found from data on ocean waters near the region the guy was trapped (Nigeria), modified to account for the cooler water under the surface. This link (http://www.unisense.com/files/PDF/Diverse/Seawater%20&%20Gases%20table.pdf http://www.unisense.com/files/PDF/Diverse/Seawater%20&%20Gas...) has these coefficients for various combinations of salinity and temperature. All of that data is for 1 bar so you'd have to modify those values for the pressure at ~30 m. 2) Set up an oxygen mass balance about a bubble of radius R. We'll assume the bubble is entirely spherical. If you consider the fact that the bubble is centered at a room corner, its radius will need to be sqrt(8) times bigger than the calculated value (since diffusion can only occur at the surface of the bubble that has contact with sea water). 3) The rate of change of O2 concentration (d_C_O2/dt) will be zero (in order for one to persist indefinitely in the bubble), and we know its value must be 15-19 vol % according to this site (http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm). 4) Set up a O2 -> CO2 "reaction" (the lungs) just to get the molar ratios of each. This is the tricky part of the problem because this depends quite a bit on human physiology, and probably varies somewhat by the individual. 5) Plug these values into the radial form of Fick's law of diffusion, and solve the resulting equation for R. [If I get more time, I'll do this rigorously.]
- marshray 13y ago
  Is there any reason to think the result would be radically different than for blood? (E.g., hemoglobin). As the first comment points out, the lungs need about 70 m^2 of surface area. So as long as the surface area of the trapped bubble-seawater interface was at least that size, perhaps you could survive indefinitely, down to the limit of air-breathing depths. In smaller bubbles, perhaps you could keep yourself alive by splashing. Like an aquarium bubbler in reverse.
  - Xcelerate 13y ago
    The problem is that the diffusion coefficient in the lungs is different than that for an air-water interface. Consider (as an extreme example) a bubble surrounded by steel with a surface area of 70 m^2. Yes, there is still diffusion of oxygen through the steel, but it's at a vastly lower rate than it is through water.
masklinn 13y ago
> The atmosphere is about 20 percent oxygen. People breathe this in, and breathe 15 percent oxygen out That's standard air pressure though. As you dive and pressure increases, the metabolized oxygen stays roughly constant (metabolic rate is independent of pressure) but the "amount" of oxygen breathed in shoots up because the inspired volume does not change either (and there's more oxygen in the same volume under pressure). Thus the "extraction efficiency" goes down (you proportionally breathe out more and more oxygen which wasn't metabolized). This is why closed-circuits rebreathers are so much more efficient than open-circuit cylinders, and the o2 cylinder is so much smaller (excluding safety cylinders): at atmospheric pressure an open circuit may "waste" 75% of the oxygen, at depth it may be >90%. A rebreather or a closed environment (under pressure) will allow much more efficient oxygen use.
OoTheNigerian 13y ago
Glad to see Nigeria is on Hacker news for positive news :)
- dia80 13y ago
  Not sure if ship sinking and 10 crew dying and 1 one barely surviving is good news... :(
gus_massa 13y ago
There is a spider that does something like this. It picks a bubble and uses it to survive underwater. The bubble exchanges some oxygen from the water, so it last more time (but not indefinitely). Link: Underwater Spider Spins Itself an Aqualung: http://news.sciencemag.org/sciencenow/2011/06/spiders.html http://news.sciencemag.org/sciencenow/2011/06/spiders.html Previous discussion (about the spider): https://news.ycombinator.com/item?id=2643142 https://news.ycombinator.com/item?id=2643142 (93 points, 734 days ago, 9 comments)
- joshschreuder 13y ago
  There's a Studio Ghibli short that they show at the museum in Japan which features a spider like this, see here: https://en.wikipedia.org/wiki/Mizugumo_Monmon https://en.wikipedia.org/wiki/Mizugumo_Monmon
chiph 13y ago
I'm curious how he didn't succumb to hypothermia. Circulating ocean water would conduct heat away from his body pretty quickly. Granted, he's near the equator, not the arctic, but still...
- ars 13y ago
  I don't think the water was circulating all the much - it was inside the vessel. It was rising, but not circulating. Also, he may have been able to stay out of it at least at first, till it rose.
benjamincburns 13y ago
Bonus points: This question assumes the interface between the water and the air is at rest. Think of a bubbler in an aquarium. Would splashing around periodically increase or decrease your survivability? That is, would the increased rate of gas exchange at the air/water interface be greater or less than the increased rate of gas exchange at the air/blood interface? Double super extra bonus points if you can plot this based on credible data. Edit: Or alternatively - what if he just breathed out through a tube placed under the water such that his bubbles were recaptured? Edit 2: I wonder if dehydration due to the salt exposure also played a role in making his situation more survivable. Would dehydration have reduced total air/blood gas exchange in a meaningful way?

196 points by Xcelerate 13y ago

From the comment that explains a lot, but misses the point completely (exchange of oxygen between the bubble and the sea to replenish oxygen in the bubble): Don't ask a chemistry question on a physics board ;-)

adamtulinius 13y ago
And in a comment to that comment: "Using imperial measures in a discussion on Physics?" hehe :-)
- Uchikoma 13y ago
  :-)

inthewind 13y ago

Related: http://www.isracast.com/article.aspx?id=63 http://www.isracast.com/article.aspx?id=63

fletchowns 13y ago
Warning: Audio will start playing on this site. Scared the shit out of me!

usaphp 13y ago

A person can survive in an air bubble but after 13 hours he will start having a trench foot condition: http://en.wikipedia.org/wiki/Trench_foot http://en.wikipedia.org/wiki/Trench_foot

mistercow 13y ago
According to the article you linked, trench foot occurs in temperatures up to 60°F. The water temperature off the cost of Nigeria this time of year is closer to 80°F, so I'm guessing trench foot wouldn't be a problem.
- jessaustin 13y ago
  The temperature at a depth of 30m is certainly not 80°F.

jlgreco 13y ago

Does anyone know how survivable rapidly surfacing from 30 meters would be? Wolfram Alpha has the pressure down there at almost 400 kPa (compared to 100 kPa) so my suspicion is "not at all", but I'm not really familiar with the tolerances and life expectancies with the bends. 30 meters is just agonizingly close to the surface though, well within what most adults could do horizontally (particularly if their life depended on it.) Being that close to the surface, but still so far away, must be absolutely awful.

fletchowns 13y ago
Probably not very survivable, given that they stuck the guy in a decompression chamber for 60 hours.
- jlgreco 13y ago
  Well yeah, but even a slight chance would be worth attempting if you were in such a position, even if it were just a 5% chance of survival, compared with the 100% chance they were probably shooting for with the 60 hour decompression. Of course if attempting it meant certain but excruciating death, then taking a shot at it would not be the way to go.
- ars 13y ago
  They left him in there for so long because he was in the water for so long. (i.e. plenty of time for nitrogen to dissolve). If he had swum up right away he would not need decompression. I imagine in the dark he would have been too scared of not being able to find the way out in the cluttered sunken vessel.
  - jlgreco 13y ago
    He probably also didn't know how close to the surface he was.
Udo 13y ago
It depends on how long you've been down there. If you have just been dragged under water with your boat, it's probably safe to make a rapid ascent (don't hold your breath though) - in fact, diving school teaches emergency ascents for situations where no other options apply, even if the diver is in need of decompression. However, after about half an hour it becomes a serious problem that gets worse over time as gases start to infuse into the tissue. If rescue (and access to a pressure chamber) is available right away, I'd make that ascent immediately even after being down there for a longer time. It beats drowning or CO2 poisoning. Dive tables illustrate pretty well how the relationship between depth and time works: http://www.naui.org/tables.aspx http://www.naui.org/tables.aspx

coldarchon 13y ago

No idea why this is on Hacker News, but the question is wrong, he has to ask when the carbon dioxide poisoning happens. Contrary to the presentation of this situation in all movies from Hollywood, it is more likely to die from carbon dioxide poisoning than from "oxygen running out".

Xcelerate 13y ago

D'oh! Just realized I was a chemical engineer an hour after I posted this :) The steps to solve this problem are pretty simple: 1) Find the diffusion coefficient of oxygen in seawater. This can be found from data on ocean waters near the region the guy was trapped (Nigeria), modified to account for the cooler water under the surface. This link (http://www.unisense.com/files/PDF/Diverse/Seawater%20&%20Gases%20table.pdf http://www.unisense.com/files/PDF/Diverse/Seawater%20&%20Gas...) has these coefficients for various combinations of salinity and temperature. All of that data is for 1 bar so you'd have to modify those values for the pressure at ~30 m. 2) Set up an oxygen mass balance about a bubble of radius R. We'll assume the bubble is entirely spherical. If you consider the fact that the bubble is centered at a room corner, its radius will need to be sqrt(8) times bigger than the calculated value (since diffusion can only occur at the surface of the bubble that has contact with sea water). 3) The rate of change of O2 concentration (d_C_O2/dt) will be zero (in order for one to persist indefinitely in the bubble), and we know its value must be 15-19 vol % according to this site (http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm). 4) Set up a O2 -> CO2 "reaction" (the lungs) just to get the molar ratios of each. This is the tricky part of the problem because this depends quite a bit on human physiology, and probably varies somewhat by the individual. 5) Plug these values into the radial form of Fick's law of diffusion, and solve the resulting equation for R. [If I get more time, I'll do this rigorously.]

marshray 13y ago
Is there any reason to think the result would be radically different than for blood? (E.g., hemoglobin). As the first comment points out, the lungs need about 70 m^2 of surface area. So as long as the surface area of the trapped bubble-seawater interface was at least that size, perhaps you could survive indefinitely, down to the limit of air-breathing depths. In smaller bubbles, perhaps you could keep yourself alive by splashing. Like an aquarium bubbler in reverse.
- Xcelerate 13y ago
  The problem is that the diffusion coefficient in the lungs is different than that for an air-water interface. Consider (as an extreme example) a bubble surrounded by steel with a surface area of 70 m^2. Yes, there is still diffusion of oxygen through the steel, but it's at a vastly lower rate than it is through water.

masklinn 13y ago

> The atmosphere is about 20 percent oxygen. People breathe this in, and breathe 15 percent oxygen out That's standard air pressure though. As you dive and pressure increases, the metabolized oxygen stays roughly constant (metabolic rate is independent of pressure) but the "amount" of oxygen breathed in shoots up because the inspired volume does not change either (and there's more oxygen in the same volume under pressure). Thus the "extraction efficiency" goes down (you proportionally breathe out more and more oxygen which wasn't metabolized). This is why closed-circuits rebreathers are so much more efficient than open-circuit cylinders, and the o2 cylinder is so much smaller (excluding safety cylinders): at atmospheric pressure an open circuit may "waste" 75% of the oxygen, at depth it may be >90%. A rebreather or a closed environment (under pressure) will allow much more efficient oxygen use.

OoTheNigerian 13y ago

Glad to see Nigeria is on Hacker news for positive news :)

dia80 13y ago
Not sure if ship sinking and 10 crew dying and 1 one barely surviving is good news... :(

gus_massa 13y ago

There is a spider that does something like this. It picks a bubble and uses it to survive underwater. The bubble exchanges some oxygen from the water, so it last more time (but not indefinitely). Link: Underwater Spider Spins Itself an Aqualung: http://news.sciencemag.org/sciencenow/2011/06/spiders.html http://news.sciencemag.org/sciencenow/2011/06/spiders.html Previous discussion (about the spider): https://news.ycombinator.com/item?id=2643142 https://news.ycombinator.com/item?id=2643142 (93 points, 734 days ago, 9 comments)

joshschreuder 13y ago
There's a Studio Ghibli short that they show at the museum in Japan which features a spider like this, see here: https://en.wikipedia.org/wiki/Mizugumo_Monmon https://en.wikipedia.org/wiki/Mizugumo_Monmon

chiph 13y ago

I'm curious how he didn't succumb to hypothermia. Circulating ocean water would conduct heat away from his body pretty quickly. Granted, he's near the equator, not the arctic, but still...

ars 13y ago
I don't think the water was circulating all the much - it was inside the vessel. It was rising, but not circulating. Also, he may have been able to stay out of it at least at first, till it rose.

benjamincburns 13y ago

Bonus points: This question assumes the interface between the water and the air is at rest. Think of a bubbler in an aquarium. Would splashing around periodically increase or decrease your survivability? That is, would the increased rate of gas exchange at the air/water interface be greater or less than the increased rate of gas exchange at the air/blood interface? Double super extra bonus points if you can plot this based on credible data. Edit: Or alternatively - what if he just breathed out through a tube placed under the water such that his bubbles were recaptured? Edit 2: I wonder if dehydration due to the salt exposure also played a role in making his situation more survivable. Would dehydration have reduced total air/blood gas exchange in a meaningful way?