As a newly certified diver and after watching a History channel program about the navy using scuba divers to tap into a soviet phone line 500' below the surface, I got to wondering if there was a limit to the depth a diver can go. So I did a little googleing and ran across this web site.
If you haven't seen this yet, some of you divers might be interested.
I see now that "theoretically" there is no limit.
http://www.wr350.com/intro/default.htm
Bob3
August 3rd, 2003, 11:35 PM
..."theoretically" there is no limit. Not to pop that bubble, but gas mixtures become too thick to breathe somewhere after 2000'. So far the deepest dives (2300') have been done using hydreliox, a hydrogen helium oxygen mix.
RichLockyer
August 4th, 2003, 12:08 AM
Not to mention tank pressures are a tangible limit. A full 3000psi cylinder would be "empty", or equalize with ambient pressure, at a little deeper than 6700ft.
Yes, that is far deeper than the 2000ft gas density limit, but it's still a reduction in available gas, and certainly a hard floor which could never be passed no matter what special gasses would be used. Even at 2000ft, you can cut nearly 1000psi from your available gas supply.
Narcosis, HPNS, O2tox, all present very real physical and logistical challenges.
For a wet dive to 2000ft, an O2 level of 1.6% would result in a PO2 of about 1.0. That would be an extremely tricky tank to mix, given that O2 analyzers are barely accurate to more than 1%, and are pretty inaccurate when you get much below 10%.
Going deeper further compounds the problem, but even a dive to 1000ft on scuba faces similar challenges.
Realistically, few of us will ever see the far side of 350ft and make it back to talk about. Deeper than that and you get into the realm of "why".
Brass bawls have no place in diving, and 300-400ft is the max depth where you can spend enough time to actually accomplish anything without incurring unrealistic decompression obligations.
Doing it to break a record is a reason, but, IMHO, it's a very stupid reason to do a high risk dive with absolutely zero benefit beyond an ego stroke.
Yes, I view freediving record attempts with the same distain, and Audrey's death was a tragic waste of human life.
Keep in mind that the divers in the link you posted were supposed to have done that dive this month.
roakey
August 4th, 2003, 12:15 AM
Here's a datapoint on hydrogem-oxygen mixtures from GUE's "Getting Clear on the Basics: The Fundamentals of Technical Diving" book:
"Furthermore, when used exclusively with oxygen, and at great depth, hydrogen has narcotic effects similar to LSD. Following deep diving trials, this mixture has been implicated in long-term phychological changes in saturation divers."
Scary stuff!
Roak
RichLockyer
August 4th, 2003, 12:20 AM
roakey once bubbled...
"Furthermore, when used exclusively with oxygen, and at great depth, hydrogen has narcotic effects similar to LSD.
Ya, but "the other guys" will say that you can get used to it :devil:
Jeez... LSD effects, HPNS... the only thing left is liquid... way more dense, but the O2 and CO2 carrying ability could allow for extremely slow respiration.
roakey
August 4th, 2003, 12:33 AM
RichLockyer once bubbled...
...the only thing left is liquid...
Ah yes, this link is good at least once a year, usually when questions about the movie "The Abyss" arise:
http://www.allp.com/LiquiVent/lv_fact.htm
Roak :)
DA Aquamaster
August 4th, 2003, 12:33 AM
HPNS is a common problem with Heliox at depths below about 600'. But ironically enough the solution to this problem is to introduce a little nitrogen into the mix. The slight narcotic effect resulting from the small amount of nitrogen prevents HPNS.
Jim Bowden and Sheck Exley attempted a 1000' dive on scuba in April 1994. Bowden dove to 925 ft, before starting his ascent due to concerns for higher than planned gas consumption and then spent nearly 10 hours decompressing. He still sufferred a DCS hit that had to be treated on site with in water recompression. Exley was less fortunate and did not survive.
No recovery was attempted but his body was recovered 3 days later while equipment was being removed from the cave as his body had drifted up and snagged on a line. His dive computer indicated a max depth of 904 ft and HPNS was suspected as the probable cause of the accident.
As far as I know 925' is still the mixed gas record for scuba. Given the level of insanity needed to attempt to break the record, I suspect it will stand awhile.
RichLockyer once bubbled...
Jeez... LSD effects, HPNS... the only thing left is liquid... way more dense, but the O2 and CO2 carrying ability could allow for extremely slow respiration.
You're forgetting about Kevin Costner's gills in "Water World". :)
You say that they should have completed the dive this month? I'm confused. Is it 2004 already?
padiscubapro
August 4th, 2003, 06:10 AM
DA Aquamaster once bubbled...
HPNS is a common problem with Heliox at depths below about 600'. But ironically enough the solution to this problem is to introduce a little nitrogen into the mix. The slight narcotic effect resulting from the small amount of nitrogen prevents HPNS.
Jim Bowden and Sheck Exley attempted a 1000' dive on scuba in April 1994. Bowden dove to 925 ft, before starting his ascent due to concerns for higher than planned gas consumption and then spent nearly 10 hours decompressing. He still sufferred a DCS hit that had to be treated on site with in water recompression. Exley was less fortunate and did not survive.
No recovery was attempted but his body was recovered 3 days later while equipment was being removed from the cave as his body had drifted up and snagged on a line. His dive computer indicated a max depth of 904 ft and HPNS was suspected as the probable cause of the accident.
As far as I know 925' is still the mixed gas record for scuba. Given the level of insanity needed to attempt to break the record, I suspect it will stand awhile.
You're forgetting about Kevin Costner's gills in "Water World". :)
on nov 6 2001 john bennet went to 308m/1010 fsw on open circuit scuba..
he used custom tables and was in the water for almost 9.5 hours
SA-Diver
August 4th, 2003, 06:27 AM
Do you have any more details - just interested.
-boltfish
August 4th, 2003, 06:52 AM
http://www.tech-dive-academy.com/journey.html
the whole story...
Tanto
August 4th, 2003, 07:08 AM
Two italians claim they dove to 320 meters, and are aiming to reach 400 meters, see the link to their web site for more...
http://www.captainnemomagazine.net/home.htm
This would have been a yoyo dive like Bennet's nothing like the cenote cave dive performed by Exley and Bowden.
-boltfish
August 4th, 2003, 10:42 AM
Is there an English translation?
roturner
August 4th, 2003, 01:49 PM
PhishSchticks once bubbled...
<snip>
I see now that "theoretically" there is no limit.
http://www.wr350.com/intro/default.htm
Well that's not quite factual. As soon as the tank pressure is too low to overcome ambient pressure then you're in the soup. Also look up HPNS. The howling kamikazes from that website you quoted will be very luck to survive their dive, IMHO.
R..
medical1
August 4th, 2003, 02:09 PM
"tandem world record scuba dive to -350 meters"
That convers to 1148.294 feet. :confused:
Phoenix
August 4th, 2003, 03:49 PM
Two british divers will be doing the world record open circuit trimix attempt in august this year in Sharm, 333 meters they aim to hit, they have been preparing for years, one of them already holds the red sea depth record, and one holds the deep air record
crazy people :)
RichLockyer
August 4th, 2003, 09:42 PM
Phoenix once bubbled...
Two british divers will be doing the world record open circuit trimix attempt in august this year in Sharm, 333 meters they aim to hit, they have been preparing for years, one of them already holds the red sea depth record, and one holds the deep air record
crazy people :)
Crazy is not the word I would use.
Crazy implies a mental illness.
Stupidity is learned.
Grajan
August 4th, 2003, 10:07 PM
roakey once bubbled...
"Furthermore, when used exclusively with oxygen, and at great depth, hydrogen has narcotic effects similar to LSD. Following deep diving trials, this mixture has been implicated in long-term phychological changes in saturation divers."
Roak
As an ex sat tech I have to wonder how you would measure "long-term phychological changes" in a typical sat diver - I've seen some things........
Bob3
August 4th, 2003, 10:17 PM
I've seen some things........ Yah, I was chuckling over that one myself; some of those buggers work better when they're narced.
boomx5
August 5th, 2003, 12:17 AM
-boltfish once bubbled...
RichLockyer
You say that they should have completed the dive this month? I'm confused. Is it 2004 already?
The date got pushed back a year, that is why he said they were supposed to do it this month.
RichLockyer
August 5th, 2003, 12:24 AM
boomx5 once bubbled...
The date got pushed back a year, that is why he said they were supposed to do it this month.
Thanks... somehow I missed that reply... I wasn't trying to ignore anyone.
jonnythan
August 5th, 2003, 08:14 PM
RichLockyer once bubbled...
Not to mention tank pressures are a tangible limit. A full 3000psi cylinder would be "empty", or equalize with ambient pressure, at a little deeper than 6700ft.
Yes, that is far deeper than the 2000ft gas density limit, but it's still a reduction in available gas, and certainly a hard floor which could never be passed no matter what special gasses would be used. Even at 2000ft, you can cut nearly 1000psi from your available gas supply.
I don't see how that's a "hard floor," since it's quite within the realm of reason that a tank could be filled with more than 3000 psi. I think humanity's engineering skills can manage that ;)
RichLockyer
August 5th, 2003, 09:42 PM
jonnythan once bubbled...
I don't see how that's a "hard floor," since it's quite within the realm of reason that a tank could be filled with more than 3000 psi. I think humanity's engineering skills can manage that ;)
3000psi perhaps... but for any pressure that we are able (or willing) to pack into a cylinder, the sea floor has an equal pressure to negate it. What's max sea floor depth.... 40,000ft? That's nearly 18,000psi.
Theoretically? There may be no limit.
Practically? Not in our lifetime.
jonnythan
August 5th, 2003, 10:54 PM
Well right now it's easy to find cylinders filled to 4500 psi, and that puts us over 10,000 feet. Who's up for it? ;)
RichLockyer
August 5th, 2003, 11:13 PM
jonnythan once bubbled...
Well right now it's easy to find cylinders filled to 4500 psi, and that puts us over 10,000 feet. Who's up for it? ;)
Don't forget... that 4500 will be EMPTY at 10,000. Even though it's full, it's equalized with ambient.
Gotta have something to breathe when you get there :naner:
jeremyrfoster
August 11th, 2003, 10:33 PM
To overcome the lack of air due to tank pressure limitations at extreme depth, couldn't you just take more tanks?
How about filling tanks once their external pressure gets closer to the internal pressure. A tank rated to 3000 psi could hold 3000 psi more once it reaches 3000psi of water, right? I don't know how this would happen... a hell of a hose I guess... or an underwater air compressor? Maybe this is "cheating".
If a support line could be dropped to the bottom of the Marianas trench with tanks all along with pressures that are 3000psi above their _ambient_ pressures, then air supply wouldn't be a limit... just the effects of the high partial pressures of the various gases on the human body.
Gas loading has limits, right? I believe the body can only load so much nitrogen, so it's not like you're looking at 4 days of decompression or something.
Just thinking. I'll think I'll stay a little closer to 1atm for the time being.
Tanto
August 12th, 2003, 02:41 AM
Gas loading has limits, right? I believe the body can only load so much nitrogen, so it's not like you're looking at 4 days of decompression or something.
The limit (saturation) is only at each given pressure, but the higher the pressure the higher the gas intake. Thus yes, you could be looking for four days of deco... or even more!
RichLockyer
August 12th, 2003, 06:18 PM
jeremyrfoster once bubbled...
To overcome the lack of air due to tank pressure limitations at extreme depth, couldn't you just take more tanks?
How many can you carry? Not enough for any significant time.
How about filling tanks once their external pressure gets closer to the internal pressure. A tank rated to 3000 psi could hold 3000 psi more once it reaches 3000psi of water, right? I don't know how this would happen... a hell of a hose I guess... or an underwater air compressor? Maybe this is "cheating".
The logistics of this would practically require a submarine to be with you. An u/w compressor?
If a support line could be dropped to the bottom of the Marianas trench with tanks all along with pressures that are 3000psi above their _ambient_ pressures, then air supply wouldn't be a limit...
Except that the hose and compressor would have to support that pressure all the way to the surface. You would only be pumping 3000psi above ambient at the max depth. For every 500ft the hose rises, it is holding back an additional 223psi compared to ambient. At 30,000ft deep, pumping into 3000psi would require nearly 17,000psi at the surface.
We're not even getting into the volume of gas consumed by the diver. At a respectable SAC rate of 0.50cfm, at 30,000ft the diver's actual inspired volume would equal 455cfm, or just over 7.5cf/second.
Yes... the diver would drain a 14ft pony in less than 2 seconds.
What size of hose is going to be needed to supply that much gas?
just the effects of the high partial pressures of the various gases on the human body.
"just" the effects? HPNS, narcosis, O2 toxicity.... mixing a tank of trimix for a 1000ft dive can be tricky. Mixing for a 5000ft dive would have you blending a tank with an O2 percentage of less than 0.01%... closer to 0.007%. Not 0.7 percent... but seven THOUSANDTHS of one percent.
Im not takin' responsibility for that mix :)
Gas loading has limits, right? I believe the body can only load so much nitrogen, so it's not like you're looking at 4 days of decompression or something.
Look again at the gas laws. The higher the pressure is, the more deeply you can saturate.
You get tired quickly when you go into the mountains because you are currently saturated with inert gasses to the pressure at sea level (roughly, depending on where you live).
You get acclimated to the mountains by.... offgassing! You dump the excess nitrogen load. Now, 5000ft of air is only equivalent to about 7ft of water, so you're in no danger of getting bent, but it still happens.
As far as deep saturation, IIRC you could theoretically spend 4 days decompressing from as shallow as 100ft if you were down long enough. Likewise, depth speeds the process. These record-breaking bounce dives where the diver just touches 900ft for a few seconds require 10-20 hours of deco, and when it was attempted by Sheck Exley, he died (suspected HPNS) and his buddy was STILL bent.
Don Burke
August 13th, 2003, 10:23 PM
You can pretty much forget carrying enough OC gas to do the bottom time and deco for even a bounce dive beyond about 600 feet. To be self-contained, rebreathers would pretty much be it.
The guys referred to in the first message were using MK11 "surface" supplied rigs or something much like them.
I was assigned to the command that had the US Navy saturation diving school and stood watches as staff duty officer. The divers told me that a rule of thumb to bring a guy up from saturation was one day per hundred feet plus a day. The Master Divers had a more exact computation, but the rule of thumb was good enough for us pencil pushers.
I expect 1 ATM suits to be the answer before they can make ambient pressure diving practical really deep.
Doc Intrepid
August 14th, 2003, 01:20 AM
involved with Bennett's dive to 1100' or so, go to the Apeks site, here:
http://www.apeks.co.uk/apekshome.htm
click in the upper left hand corner, and the section of the site regarding Bennett is one of the following bullets.
sasdasdaf
August 14th, 2003, 10:46 AM
RichLockyer once bubbled...
Crazy is not the word I would use.
Crazy implies a mental illness.
Stupidity is learned.
Exactly what I was thinking... I think we have had enough injuries and deaths already from chasing records.
DeepSeaDan
August 25th, 2003, 04:56 PM
Hello folks,
During my 10 year run as a commercial oilfield diver I did about 100 days of sat. ( not much in comparison to other guys I know; ie: numerous years of month in/ month out! ).
My deepest foray was to 720'. All told, I did 55 days stored at that depth & 15 days travelling to surface ( normal deco. from that depth was 5.5 days.)
That pressure was hard on the joints! To this day my shoulder joints still seem to "dry out" at depth & get quite "noisy".
I've talked to numerous hyperbaric physicians/researchers over the years, but it appears there is precious little data available still on the chronic effects of inert gas exchange in our tissues. Apparently, the major commercial diving contractors will not share their data with the medical community thus a major source of information for many aspects of hyperbaric research remains inaccessible.
I'm a shallow water puppy now - I figure I've taken enough risks with my physiological well-being for one life; besides, the waters warm, clear, & the visits are long...
