Thinking about deep-water dives and the movie Abyss.

MrWizzard

Platinum Member
Mar 24, 2002
2,493
0
71
You know the sub launching room with the pool of water. In theory if the underwater habitat were deep enough, wouldn?t jumping into the ?moon pool? or ?sub launching pen? be instant death? The water in those pools would be the pressure of whatever depth the base was at right. So you would jump in and be crushed? Or at least have all the air in your lungs pushed out.


If there were enough pressure from the water the air in the whole habitat would be higher pressure than air at the surface of the ocean because it has to be enough to keep the water out right? Unlike a fully enclosed sub having a launching pen that is exposed like that would cause the air to be 2 to 3x as dense?

Do my ramblings make sense? Any divers able to offer wisdom?
 

PricklyPete

Lifer
Sep 17, 2002
14,714
164
106
I have no idea about that question...but I'm a fan of the movie regardless of how many holes there are in the story.
 

zinfamous

No Lifer
Jul 12, 2006
110,806
29,557
146
Originally posted by: PricklyPete
I have no idea about that question...but I'm a fan of the movie regardless of how many holes there are in the story.

:thumbsup:

The Abyss is awesome.
 

Maiora

Senior member
Oct 9, 1999
370
0
0
It's equalized. This is why if one comes up to the surface they must stay in a decompression chamber. At that pressure and depth it would be days. Too soon and you get the bends.

Remember at the end where Lindsay says "We should be dead. We didn't decompress!"

That's why but of course their "friends" took care of that for 'em.
 

bonkers325

Lifer
Mar 9, 2000
13,077
1
0
assuming the "underwater pool" is open and connected to the surrounding waters, then there the diver would be crushed instantly upon entering the chamber as the air pressure needs to equal the water pressure for the water to be in equilibrium.
 
Aug 23, 2000
15,511
1
81
Originally posted by: bonkers325
assuming the "underwater pool" is open and connected to the surrounding waters, then there the diver would be crushed instantly upon entering the chamber as the air pressure needs to equal the water pressure for the water to be in equilibrium.

But it's already equal as the drilling rig has been down there long enough to equalize pressure with the water depth.
 

skyking

Lifer
Nov 21, 2001
22,215
5,075
146
The pressures are equalized for that pool to exist. The diver is already at that pressure, so he won't be crushed or suffer any ill effects. A dive to a depth 75 feet below the habitat would have a similar effect as a dive to 75 feet below the surface for you and me.
The alternative to an equalized system is really dangerous and insane. Try to maintain a sea-level atmosphere in a hard habitat, and go out in hard suits. If anything goes wrong at all you are dead.
 

tboo

Diamond Member
Jun 25, 2000
7,627
1
81
Great flick.

When are they going to release The Abyss & True Lies on DVD in anamorphic widescreen? Or have they already?
 

CZroe

Lifer
Jun 24, 2001
24,195
856
126
Originally posted by: MrWizzard
You know the sub launching room with the pool of water. In theory if the underwater habitat were deep enough, wouldn?t jumping into the ?moon pool? or ?sub launching pen? be instant death? The water in those pools would be the pressure of whatever depth the base was at right. So you would jump in and be crushed? Or at least have all the air in your lungs pushed out.


If there were enough pressure from the water the air in the whole habitat would be higher pressure than air at the surface of the ocean because it has to be enough to keep the water out right? Unlike a fully enclosed sub having a launching pen that is exposed like that would cause the air to be 2 to 3x as dense?

Do my ramblings make sense? Any divers able to offer wisdom?

Man, you failed hard at comprehending the movie. They weren't at an "insane" depth for equalizing the atmospheric pressure, thus it *was* equal. The underwater rig is beyond the scope of current endeavors, but that was a given, being "experimental" and all.

Anyway, you can't significantly compress a liquid under pressure but you can compress a gas until the pressure matches the force exerted against it* thus, without any sort of chamber-locking systems, the air MUST be equalized or else the water would rush in and fill the habitat. Obviously there were no chamber locks (they would swim in and out) and they out-right reference the higher air pressure, "bends" and other effects, decompression, etc, many times.

*this is the principle in effect in a Larami Super Soaker water cannon and why they say to leave the reservoir tank ~1/3 empty when filling.

Originally posted by: her209
I couldn't get over the whole breathing liquid oxygen thing.

It's not liquid oxygen. It's oxygenated liquid. My teacher told me about that stuff before the movie existed and it blew my 9-year-old mind.

Originally posted by: tboo
Great flick.

When are they going to release The Abyss & True Lies on DVD in anamorphic widescreen? Or have they already?

I'm pretty sure Abyss SE has had anamorphic all along. IIRC, it was selectable in the menus or on one of the other discs. IIRC, you had to dig DEEP to a second set of menus or something. I had multiple versions including the first edition that was $40. Bought it in the '90s. Probably never watched it since it was lost and before that it was on a Sigma Designs REALmagic Hollywood+ decoder card (did not watch it anamorphically).

True Lies though? Wouldn't know, though I'd like to grab that "You're fired" clip from it.

Anyway, despite JC's typical "cheesy over-stated characters," the movie was well acted and pretty ground-breaking in many ways (practical effects, special effects, etc), so I don't know why anyone would be concerned about the "quality" of the story itself, especially the SE.
 

NFS4

No Lifer
Oct 9, 1999
72,647
27
91
Originally posted by: zinfamous
Originally posted by: PricklyPete
I have no idea about that question...but I'm a fan of the movie regardless of how many holes there are in the story.

:thumbsup:

The Abyss is awesome.

Agreed. Is it out on Blu-ray yet?

And is it just me, or does James Cameron have a hard-on for Michael Beihn?
 

biggestmuff

Diamond Member
Mar 20, 2001
8,201
2
0
Originally posted by: tboo
Great flick.

When are they going to release The Abyss & True Lies on DVD in anamorphic widescreen? Or have they already?

I don't think they ever are. It pisses me off because The Abyss is one of my faves. It really looks like ass blown up on my 61" DLP (no braggart).
 

911paramedic

Diamond Member
Jan 7, 2002
9,450
1
76
Originally posted by: skyking
The pressures are equalized for that pool to exist. The diver is already at that pressure, so he won't be crushed or suffer any ill effects. A dive to a depth 75 feet below the habitat would have a similar effect as a dive to 75 feet below the surface for you and me.
The alternative to an equalized system is really dangerous and insane. Try to maintain a sea-level atmosphere in a hard habitat, and go out in hard suits. If anything goes wrong at all you are dead.

Yes, the inside of the habitat and the ocean pressures are the same, it's called saturation diving. They wouldn't be breathing air at that depth though because of nitrogen narcosis. (google it, too much to explain) That's why saturation divers sound funny, they are breathing heliox, tri-mix, or some variant.

And you wouldn't be crushed if you were suddenly at that depth, but your air cavities would if you couldn't equalize them fast enough. (Probably couldn't, so you would end up collapsing some lungs, sinus cavities, and blowing out both ears.) SCUBA equipment senses pressures and that's how you don't feel any different when diving, the air pressure delivered is the same as the surrounding depth.

I don't know what depth they were (also one of my favorites) but you can calculate it at 0.445 psi per foot of depth. It would take them a LONG, LONG time to resurface and decompress from being at that pressure for so long.
 

Modelworks

Lifer
Feb 22, 2007
16,240
7
76
Originally posted by: tboo
Originally posted by: her209
I couldn't get over the whole breathing liquid oxygen thing.

Perfluorocarbons

Yep and the scene they did with the mouse was real. It really did get submerged in the liquid and breathe it.


About the topic.
It is called a moon pool. Don't know why.
http://en.wikipedia.org/wiki/Moon_pool
If a submerged chamber with a moon pool is holed in the floor, there is no change to the moon pool water level or the air pressure inside the chamber ? it has no effect. If such a chamber is holed in its side or roof, many might predict that water would squirt or gush in through the hole and flood the chamber, as it would in a submarine. In fact this scenario is completely incorrect: instead air will leak out of the hole into the water and prevent water coming in, even if the hole is very large, and the surface level of the moon pool will rise up into the chamber until it reaches the top of the hole, at which point it will stop rising, air will stop escaping, and an air space will be left above the hole.

This is because the air in the chamber has a pressure higher than the water on the outside of the hole. The air pressure in the chamber equals the water pressure at the surface of the moon pool, the water pressure at the hole is less than this by an amount determined by the height difference between hole and moon pool surface. If the hole is 2.4 m higher than the moon pool surface, using the divers' rule of thumb, the air pressure will be 0.24 atm (about 3.5 PSI) higher than the water on the outside of the hole. This figure does not vary with the depth of the chamber below sea level. Compare the situation with a submarine having an internal air pressure of 1 atm. At a hole in its hull 20 m below sea level, the seawater will have a pressure 2 atm (30 PSI) higher than the air and will come through the hole as a jet.
 

TheSlamma

Diamond Member
Sep 6, 2005
7,625
5
81
Diving Bells

When I was getting my rescue certification the DM assisting my instructor in training used to be a commercial diver in the Bering Sea, dude did some very deep dives using this kind of tech.
 

tboo

Diamond Member
Jun 25, 2000
7,627
1
81
One of my fears of dying would be to go the way Biehn's character went in that movie.
 

Modelworks

Lifer
Feb 22, 2007
16,240
7
76
Originally posted by: TheSlamma
Diving Bells

When I was getting my rescue certification the DM assisting my instructor in training used to be a commercial diver in the Bering Sea, dude did some very deep dives using this kind of tech.

At one point in my past I considered getting certified for deep sea diving. I have a friend that is a deep sea welder and makes $125 / hour + hazard pay.
 
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