A really noob question...

Xelif · 06-17-07, 07:33 PM

As far as I know, they use a CO2 meter because that's what is most important. When you're underwater for great lengths of time, I believe the buildup of carbon dioxide becomes toxic more quickly than a lack of oxygen. Think of the spacecraft Apollo 13 and the movie about it - CO2 buildup was the problem, not a lack of oxygen.

I know that the human brain detects/signals the need to breathe by sensing rising blood acidity - this is caused by increased carbon dioxide dissolving into ah carbonic acid I believe in the blood. So our brains detect CO2 levels in the blood rather than oxygen levels

GTHammer · 06-17-07, 08:53 PM

Ok this might be a dumb questions/series of questions but...

How do they deal with the CO2? Do they use scrubbers like on space craft? If so then shouldn't they be able to just change the filters and with enough filters etc then shouldn't they be able to stay down as long as they have fresh Oxygen to add to the air?

Xelif · 06-17-07, 09:58 PM

I have no clue about the air systems on WW2 subs. I believe I have read about oxygen candles, and maybe even the use of lime to counteract acidic carbon dioxide in various forms... but I have no references! Whee. How useful. I also think the terms 'oxygen' and 'air' may be used interchangeably in some contexts, further confusing in my mind what exactly is going on - O2 added, CO2 removed, or both?

Perhaps the technology wasn't quite advanced enough by that point to allow full air rebreathers. I know that as a technology for divers, air rebreathers weren't available until some time after the war. By air rebreathers, I mean a technology that processes your exhaled air to remove the CO2 and add in O2, or a technology that strips that pesky carbon and returns O2 directly... It might have been a low priority in research back then.

Nuclear subs generate O2 by splitting water, as far as I know, but I don't know how they get rid of the CO2. Filters can be annoying as they have to be replaced, I know that much, and nuclear subs are legendary for submerged duration. Venting would be a simple option.

Powerthighs · 06-17-07, 10:32 PM

I believe the CO2 in nuclear subs is removed from the air through a chemial process.

Centred75 · 06-17-07, 10:56 PM

Other than the lime absorbant which was usually used only in emergencies (as it was pretty much one time use only, like your brita/pur water filters) submarines of that age just let the CO2 build up in the air (hense the CO2 meter). Subs were designed in such a manner as to allow them to operate submerged long enough that the batteries would run dry before the CO2 levels became dangerous. If situations prevented the sub from surfacing (say they had to sit silent without running engines for over two days) they would crack open the lime to remove the built up CO2.

SteamWake · 06-18-07, 10:10 AM

Quote:

Originally Posted by Centred75

Other than the lime absorbant which was usually used only in emergencies (as it was pretty much one time use only, like your brita/pur water filters) submarines of that age just let the CO2 build up in the air (hense the CO2 meter). Subs were designed in such a manner as to allow them to operate submerged long enough that the batteries would run dry before the CO2 levels became dangerous. If situations prevented the sub from surfacing (say they had to sit silent without running engines for over two days) they would crack open the lime to remove the built up CO2.

Run submerged at 2 or 3 knots untill the batteries are flat see which runs out first O2 or the batteries.

The 'air' is refresed very quickly and its easy to miss the notice that has been replenished. Only a brief surface is needed for a gulp of fresh air.

06-17-07, 08:53 PM	#2
GTHammer Machinist's Mate Join Date: May 2007 Location: Iowa Posts: 127 Downloads: 4 Uploads: 0	Ok this might be a dumb questions/series of questions but... How do they deal with the CO2? Do they use scrubbers like on space craft? If so then shouldn't they be able to just change the filters and with enough filters etc then shouldn't they be able to stay down as long as they have fresh Oxygen to add to the air? __________________ GT USS Hammer

06-17-07, 07:33 PM	#1
Xelif Seaman Join Date: Dec 2006 Posts: 37 Downloads: 0 Uploads: 0	As far as I know, they use a CO2 meter because that's what is most important. When you're underwater for great lengths of time, I believe the buildup of carbon dioxide becomes toxic more quickly than a lack of oxygen. Think of the spacecraft Apollo 13 and the movie about it - CO2 buildup was the problem, not a lack of oxygen. I know that the human brain detects/signals the need to breathe by sensing rising blood acidity - this is caused by increased carbon dioxide dissolving into ah carbonic acid I believe in the blood. So our brains detect CO2 levels in the blood rather than oxygen levels

06-17-07, 09:58 PM	#3
Xelif Seaman Join Date: Dec 2006 Posts: 37 Downloads: 0 Uploads: 0	I have no clue about the air systems on WW2 subs. I believe I have read about oxygen candles, and maybe even the use of lime to counteract acidic carbon dioxide in various forms... but I have no references! Whee. How useful. I also think the terms 'oxygen' and 'air' may be used interchangeably in some contexts, further confusing in my mind what exactly is going on - O2 added, CO2 removed, or both? Perhaps the technology wasn't quite advanced enough by that point to allow full air rebreathers. I know that as a technology for divers, air rebreathers weren't available until some time after the war. By air rebreathers, I mean a technology that processes your exhaled air to remove the CO2 and add in O2, or a technology that strips that pesky carbon and returns O2 directly... It might have been a low priority in research back then. Nuclear subs generate O2 by splitting water, as far as I know, but I don't know how they get rid of the CO2. Filters can be annoying as they have to be replaced, I know that much, and nuclear subs are legendary for submerged duration. Venting would be a simple option.

06-17-07, 10:32 PM	#4
Powerthighs Beach Leaf Join Date: Apr 2007 Location: Seattle, WA Posts: 287 Downloads: 11 Uploads: 0	I believe the CO2 in nuclear subs is removed from the air through a chemial process.

06-17-07, 10:56 PM	#5
Centred75 Watch Join Date: Jun 2007 Posts: 21 Downloads: 0 Uploads: 0	Other than the lime absorbant which was usually used only in emergencies (as it was pretty much one time use only, like your brita/pur water filters) submarines of that age just let the CO2 build up in the air (hense the CO2 meter). Subs were designed in such a manner as to allow them to operate submerged long enough that the batteries would run dry before the CO2 levels became dangerous. If situations prevented the sub from surfacing (say they had to sit silent without running engines for over two days) they would crack open the lime to remove the built up CO2.