How can a human go deeper than a submarine?

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How can a human go deeper than a submarine?
« on: 07/03/2009 11:30:02 »
Gordon asked the Naked Scientists:

Would you please explain why a human can scuba dive to lest say 100 meters by a submarine requires a very strong hull to go to that depth? Why doesn't get crushed.

thank you

What do you think?



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How can a human go deeper than a submarine?
« Reply #1 on: 07/03/2009 11:57:28 »
The human diver is subjected to all the pressure whilst down there - at 100m, the pressure is more than ten times atmospheric pressure.
A submarine's pressure hull provides atmospheric pressure for its inhabitants and protects them from the ambient pressure. This means that they can stay there indefinitely; unlike the free diver, who is subjected to the effects of gases at high pressure and will get decompression sickness (the bends), various narcoses and also bone damage. The forces on a hull are huge, but not a big deal for modern designs.
Providing a safe environment at greater depths involves many serious technical difficulties; even getting an electrical cable connection through the hull is difficult. Insulation can be squeezed through a gap like toothpaste with the sort of pressures encountered.


Offline ukmicky

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How can a human go deeper than a submarine?
« Reply #2 on: 07/03/2009 14:24:19 »
On a slightly different subject here is a crab bein sucked into a 3mm hole , you can just make out the saw cutting the hole in the pipe line

Shame about the quality



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How can a human go deeper than a submarine?
« Reply #3 on: 07/03/2009 15:49:43 »
How amazing - that'll larn it. [:o]


Offline yor_on

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How can a human go deeper than a submarine?
« Reply #4 on: 07/03/2009 21:03:26 »
It's two different ways of existing under water.
A submarine uses a rigid hull as the barrier separating the water pressure from the people inside it. When a Whale dives the hull will be its own body exhibiting an elasticity that is very different from the concept of an submarine.

"the primary anatomical adaptations for pressure of a deep-diving mammal such as the sperm whale center on air-containing spaces and the prevention of tissue barotrauma. Air cavities, when present, are lined with venous plexuses, which are thought to fill at depth, obliterate the air space, and prevent "the squeeze." The lungs collapse, which prevents lung rupture and (important with regard to physiology) blocks gas exchange in the lung. Lack of nitrogen absorption at depth prevents the development of nitrogen narcosis and decompression sickness. In addition, because the lungs do not serve as a source of oxygen at depth, deep divers rely on enhanced oxygen stores in their blood and muscle. "

You live already under one atmospheres pressure without noticing it at all.
Divers have gone down to around six hundred meters depth surviving the pressures. "A Navy diver submerged 2,000 feet(609.6 m), setting a record using the new Atmospheric Diving System (ADS) suit, off the coast of La Jolla, Calif., Aug. 1 2007" How deep we can dive and survive? Anyones guess. "On of the limiting factors in super-deep diving other than gas/blood chemistry, inert gas absoprtion, etc. is that, at a certain pressure and higher, some proteins tend to denature, which in this case, is most notable and detactable in increasing neuropathy. Give a "perfect" gas mixture, this would eventually be likely to prove fatal"

Diving to below 180 metres of seawater (msw) has been performed both as simulated onshore dives- for example, the Sagittaire and Atlantis series' and as open sea dives. It has been concluded that divers can be safely compressed to depths as great as 686 metres of seawater (msw).' Since 1980 eight simulated deep dives from 350 to 500 msw, corresponding to ambient pressures of 3 6 to 5 1 MPa, have been performed at the Norwegian underwater Technology Centre. The increased hyperbaric pressure influences the nervous system during deep dives. The divers may experience hand tremor, postural instability, gastrointestinal problems, somnolence, and cognitive dysfunction. The neurological symptoms and signs that may occur have been termed the high pressure neurological syndrome (HPNS). This syndrome has been known for more than twenty years."
A recent test of 100 deep divers in the range 22-48 years with an average age of 34 years reported that.

"The divers reported significantly more symptoms from the nervous system. Concentration difficulties and paraesthesia in feet and hands were common. They had more abnormal neurological findings by neurological examination compatible with dysfunction in the lumbar spinal cord or roots. They also had a larger proportion of abnormal electroencephalograms than the controls. The neurological symptoms and findings were highly significantly correlated with exposure to deep diving (depth included), but even more significantly correlated to air and saturation diving and prevalence of decompression sickness. Visual evoked potentials, brainstem auditory evoked potentials, and magnetic resonance imaging of the brain did not show more abnormal findings in the divers. Four (10%) divers had had episodes of cerebral dysfunction during or after the dives, two had had seizures, one had had transitory cerebral ischaemia and one had had transitory global amnesia. It is concluded that deep diving may have a long term effect on the nervous system of the divers."

Did you know that whales also suffers from 'divers bends'

"Michael J. Moore and Greg A. Early of the Woods Hole Oceanographic Institution found evidence of the bends in bones of modern sperm whales, but they also found the same damaged skeletons in whale bones up to 111 years old.

This suggests, said Moore, that sperm whales are neither anatomically or physiologically immune from the effects of deep diving, even though they spend much of their 70-year lifetime at great ocean depths. "

And that one of the reasons for them loosing it, going up to fast, getting divers bends and then possibly become stranded in the process is us :) We use a lot of acoustic devices in our submarines and they react to those. "A study last year found that some beaked whales that beached themselves in the Canary Islands after a military sonar test bore evidence of suffering from decompression illness, suggesting they were rapidly driven to the surface by noxious underwater sounds."
« Last Edit: 07/03/2009 21:25:44 by yor_on »
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