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Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

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Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#71

Post by robocat »

MisterTea wrote: post #65
LeifCarrotson wrote: post #6

Earlier quoted context omitted.

Additionally, a bag of air of that volume would not give much time underwater - maybe an extra breath or two. The extra effort and drag of carrying the bag would make it less effective than just diving. A modern steel SCUBA tank is typically pressurized to 200 bar, or about 3000 psi, making it 200x more useful than a bag. An inflatable ball is only inflated to about 0.5 bar/8 psig, human lungs are only capable of abo…

When I was a kid we had an above ground pool that was about 3 feet/~1 m deep. One day in the shed I found a 6 foot/2m length of hose that looked to be about the same diameter as the tube on the my little snorkel. Ah ha! I can attach this to my snorkel, tie the other end to a pool float and breath under water like a diver! My idea did not work out as planned. At the surface I was able to breath through the hose but on…

That was dangerous due to the risk of hypercapnia: "increased CO2 levels could lead to unconsciousness which, if happening while in the water, can result in drowning.". Note that our breathing is regulated by the amount of CO2 in our bloodstream, not the amount of oxygen. There is a fantastic explanation of the danger here: https://blog.daneurope.org/en_US/blog/are-full-face-snorkeli... There are safety regulations to limit the volume of air inside a snorkel (the dead space).

"Snorkels constitute respiratory dead space. When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again, reducing the amount of fresh air in the inhaled volume, and increasing the risk of a buildup of carbon dioxide in the blood, which can result in hypercapnia. The greater the volume of the tube, or the smaller the tidal volume of breathing, the more this problem is exacerbated." —https://en.wikipedia.org/wiki/Snorkel_(swimming)

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#72

Post by spywaregorilla »

dakial1 wrote: post #43
pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

I think it is settled among historians that this is a flotation device. There are multiple descriptions about it around: ( http://www.iro.umontreal.ca/~vaucher/History/Prehistoric_Cra... )

I wonder if the scene depicted is much of an action scene then, or if the archer is just there because they're soldiers. I'd imagine swimming with this goat bag is hardly tactically viable in almost any situation.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#74

Post by mc32 »

muleroid wrote: post #73

One thing I haven't seen mentioned which jumped out to me about the first theory is how would they have inflated the bag with breathable air in the first place? Were air pumps around back then?

I imagine you could have two bags, one big one, connected to a smaller one and squeeze air from the bigger into the smaller (many ways)... but sheepskin isn't going to hold a lot of pressure and would just bust (not sure but not as good as a soccer ball) and given it's "hotdog" shaped and not spherical, it's probably not more than 2 - 4 psi.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#75

Post by bscphil »

robocat wrote: post #71
MisterTea wrote: post #65

Earlier quoted context omitted.

When I was a kid we had an above ground pool that was about 3 feet/~1 m deep. One day in the shed I found a 6 foot/2m length of hose that looked to be about the same diameter as the tube on the my little snorkel. Ah ha! I can attach this to my snorkel, tie the other end to a pool float and breath under water like a diver! My idea did not work out as planned. At the surface I was able to breath through the hose but on…

That was dangerous due to the risk of hypercapnia: "increased CO2 levels could lead to unconsciousness which, if happening while in the water, can result in drowning.". Note that our breathing is regulated by the amount of CO2 in our bloodstream, not the amount of oxygen. There is a fantastic explanation of the danger here: https://blog.daneurope.org/en_US/blog/are-full-face-snorkeli... There are safety regulations t…

> When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again

For a long snorkel, you would want to exhale through your nose.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#76

Post by trutannus »

pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

Given how it's nearly impossible to breathe under water without the air itself being pressurized, I highly doubt option one. If you ever tried breathing out of a tube underwater as a kid, you'll know exactly what I mean.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#77

Post by Gustomaximus »

trutannus wrote: post #76
pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

Given how it's nearly impossible to breathe under water without the air itself being pressurized, I highly doubt option one. If you ever tried breathing out of a tube underwater as a kid, you'll know exactly what I mean.

I've done this with a tube as a kid and get what your saying. But would a goat skin underwater be the same? The tube example is because of the pressure difference. Having a bladder underwater the air would easily come out to breath. IMO the harder thing would be getting the bladder to stay underwater, especially at the picture size, that would have a heap of buoyancy to offset.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#78

Post by sigy »

pbhjpbhj wrote: post #16

Fascinating, the second image attached to https://twitter.com/FedeItaliano76/status/143532682797161267... is good too -- I'm not settled in that confirming the second hypothesis (surface use), as the Twitter user says, it seems to me to also give stronger weight to the first (under water use). In this image the 'goatskin' users appear fully clothed in dresses (could they be scale armour or other weighted clothing), o…

The divers can not inflate it further once submerged, yet have put their mouths on the container.

Even as a "re-breathing" container, having that reserve of air volume would allow for extended lingering time below the surface, as it would take much longer for the CO2 saturation to become a problem than just a lung full of air.

Thus, this likely served two purposes. 1) buoyancy to counter the weight of armor, and 2) additional time underwater by rebreathing (more) stale air than one can hold in their lungs.

Think about it, what would you do?

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#79

Post by nradov »

Retric wrote: post #69
nradov wrote: post #63

Earlier quoted context omitted.

Mindset and breathing technique is certainly important in minimizing open circuit gas consumption, but it's not the only factor. Some people just have a naturally higher tolerance for CO2 loading (the instinct to breathe is driven more by increase in CO2 levels rather than lack of O2). Perfect buoyancy control helps a lot since you're not wasting energy on depth keeping. Equipment configuration should be streamlined…

That’s true, but irrelevant in this case as in the short term people are O2 limited not CO2 limited which is why the world record for holding ones breath goes up by breathing pure oxygen. It’s also one of the reasons I was asking for examples as I assumed you where making assumptions that didn’t apply.

For the vast majority of people that's just wrong. The urge to breathe is driven primarily by increasing blood CO2 levels (hypercapnia). You can learn to tolerate higher levels but to reach the point where pre-breathing pure O2 makes a difference takes extensive dedicated apnea training.

Anyone can extend breath hold times at least a little by hyperventilating first to drive down CO2 levels, thus surpressing the urge to breathe. That can be dangerous underwater as it becomes easier to go hypoxic before the urge to breathe gets overwhelming.

https://pubmed.ncbi.nlm.nih.gov/17274316/

I am pretty well aware of what applies here.

Re: Assyrian soldier diving with an inflatable goatskin bag (ca. 865–860 BC)

#80

Post by nradov »

trhway wrote: post #67
killjoywashere wrote: post #36

Earlier quoted context omitted.

The work of submerging air at atmospheric pressure vastly exceeds the potential energy value extractable from the oxygen in terms of ATP. He's using it to float.

>The work of submerging air at atmospheric pressure vastly exceeds the potential energy value extractable from the oxygen in terms of ATP. He's using it to float. he is wearing some armor, definitely head helmet - that allows to balance the floatation, and would be beyond most human capabilities without the goatskin. So he achieves 2 goals simultaneously - extra air for prolonged diving as well as diving while donnin…

If you think there are no issues then try it yourself with an inflatable beach ball and some weights in the shallow end of your local swimming pool. Be sure to record a video: it's going to be hilarious watching you flail around underwater while making no forward progress.
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