It is all the beans that they serve take on a gaseous form.
IIRC …
WWII boats didn’t really have CO2/O2 exchange systems that worked real well or on the early ones worked at all. So on the surface they’d pump up high pressure tanks with air. Then while submerged whenever the air quality got too bad they’d vent some of that fresh air into the boat to dilute the bad air. They had no way to remove the volume of bad air, even if they could alter its chemistry. So this was a purely additive process.
Given they were only submerged for the best part of one day, this was a tolerable system. Obviously it wouldn’t work for modern boats that stay submerged for months.
But it did mean that once surfaced they had to vent the incremental air pressure slowly. Then flush the whole boat with fresh air, refill those tanks, and submerge again before sunrise.
Decompress?
Not to any great degree, although kaylasmom would sometimes complain about me being a little distant for a few days following a long operational run…
In regards to scuba diving, this is really hard to understand intuitively, because every diver knows that you use more air the deeper you go. It’s more difficult to understand because of the way PADI teaches about pressure and depth. I’m not sure if other dive instruction programs are better about this, but PADI illustrates depth with a balloon model. It’s accurate and useful in discussing the dangers of ascending but also confusing. If my lungs are smaller and the tank is sealed, I would expect to use less air, so WTF? The thing is, lungs aren’t passive balloons and regulators are what make diving possible, yet they’re never really explained in PADI OW or even AOW certification training.
If I take a balloon with 6 cubic liters of air at surface (1 atm and average lung capacity) to 2 atm (10 meters or roughly 33 feet) the volume of the balloon will halve to 3 cubic liters. It will halve again at 20 meters to 1.5 cubic liters and by the time I reach 30 meters (very rough limit for recreational diving) my 6 liter balloon is .75 cubic liters or 1/8th of its original size. Your lungs would not be happy with this situation and you would have to hyperventilate to survive, which would not make the your brain happy and you would pass out and die.
The entire purpose of a regulator is to take high pressure air from a tank that usually starts at about 3000psi and make it breathable at all depths. The first stage regulates 3000psi to about 150psi. That’s the easy part, but 150psi is not fun to breath either. The second stage is the brilliant part of a regulator and what makes scuba diving possible. Second stage is the part you put in your mouth and it’s based on a diaphragm system that allows you to breath in one side and then backfills the other side, based on the ambient water pressure, so the pressure in the regulator always feels close to natural breathing.
That was kind of an aside, but the point is that your lungs stay at their natural capacity at any depth underwater. They’re not tiny, they just use a lot more gas as you get deeper. That’s exactly what a regulator allows you to do.
However, all of this explains the difference between a diver and and a person on a submarine. When you’re on a sub, your environment is sealed. There is no immediate pressure on your lungs or the rest of your body like there is on a diver. It’s that physical pressure on a diver’s body that pushes nitrogen from the gas they’re breathing into their bloodstream. It’s also why lower nitrogen breathable gasses like nitrox and tri-mix are sometimes used.
Decompression is completely about off-gassing nitrogen. Decompression sickness happens when you have too much nitrogen in your bloodstream that will stay in solution under pressure, but turn to bubbles under too little pressure. For a practical example, open up a bottle of warm tonic water sometime. Anyway, that’s why submariners don’t have to decompress and divers sometimes do.
Just to be contrarian, I’d like to point out that there are deep-dive research submarines that are pressurized. (Think about the film The Abyss; all the underwater vehicles in that film were pressurized. Yes it was a movie, but the equipment was all based on real equipment that exists today.) And those submarines would require either very slow ascents, or long periods of decompression on the surface.
However, when most people say “submarine” they mean the military type, for which see above discussion.
The emergency equipment the US sent to Argentina while assisting in locating their lost military submarine included a pressurized mini-sub: https://news.usni.org/2017/11/18/u-s-submarine-rescue-equipment-crews-set-arrive-argentina-sunday-u-k-ice-patrol-ship-joins-search-missing-submarine
I’m going to amend my post and say I think that the pressure in the sub stays almost exactly at sea level pressure. I doubt on a modern sub there’s much of a pressure difference when they surface.
The reason is that if you think about how the life support system must work, it’s as follows :
There are 2 main systems. A CO2 scrubbing system, and an oxygen replenishment system.
The CO2 scrubbing system runs cabin air over some type of absorbant material. I have read that the primary method is some kind of amine cycle using urea and that it makes the submariners stink like pee afterwards. Other methods exist.
So now pressure in the sub is dropping, as the crew inhale Oxygen + inert/unused gas and exhale CO2 + inert/unused gas. The consumption of oxygen would reduce pressure in the sub.
Another system has a supply of oxygen. It most likely has both oxygen in compressed gas tanks (or liquid) and electrolyzers to make more from seawater if it is a nuclear sub.
The basic control logic for the machine is going to be :
if ((pressure < sea level pressure) || (partial pressure O2 <threshold))
Open valve to tank.
else
close valve to tank
Technically it’s going to be a slightly more complex method involving derivatives and micro-adjustments to that valve, probably.
So if the sub dives suddenly, temporarily the pressure in the sub is going to rise slightly from the hull compressing, but over time, the crew consuming the oxygen combined with the oxygen replenishment system holding back it’s servo valve until the pressure drops below sea level pressure again will mean the pressure inside stabilizes at exactly sea level pressure.
The reason the control logic also looks at partial pressure of O2 is that if something goes badly wrong and the sub atmosphere gains too much nitrogen somehow (I don’t know how this could happen), you want to make sure the partial pressure of oxygen remains high enough for the crew to remain conscious and functional so they can fix whatever is wrong. So you don’t let it fall lower than about the partial pressure of O2 at 5000 feet or so.
I was a Submarine Sonar Technician during the Cold War. The pressure within the pressure hull was, during my time, maintained at sea level pressure, + or - 1" of mercury. We actually had an aircraft altimeter mounted on the BCP (Ballast Control Panel) that was reset to 0ft when we came up to ventilate. When it read + or - 1000ft it was time to go up and equalize (mission permitting). Basically we surface, equalize, open the hatches. No muss, no fuss, no silly decompression required.
As an addendum. The “floating decks” were primarily for sound isolation. Equipment or decks hard mounted to the hull transmitted large quantities of sound into the water (bad juju for a submarine). However, not all US boats were so built. The Skipjack class (and SSBN’s based on that design) had hard mounted decks and were somewhat less quiet than the later Permit and beyond classes. However, they were still significantly more stealthy than their Soviet counterparts.
An amine system is indeed used that has a pervasive acrid smell that seeps into all of your clothes. Not at all like a urine smell, though, IMHO. You stop smelling it after a few hours onboard.
However, after getting off the boat following time at sea, I would typically lug all my gear (including laundry) home in a bag and throw it into the corner of a room. The next time I did laundry, I’d open the bag, and the smell was unmistakable.
Ah yes, that lovely amine stench. Twas especially lovely when, 3 weeks from end of patrol, the stock of fresh amine runs low and the A-divvers start stretching it. Whole boat starts to smell like a freshly opened bottle of ammonia. Takes a week to wash that smell out of your clothes after making port.
If the CO2 removed from that amine cycle is being tanked or pumped overboard, the net pressure inside the sub is going to drop, right? And then you can add O2 to keep the pressure inside the sub exactly the same as at the surface.
I’m wondering how you ended up with a whole inch of mercury difference between surface pressure and sub pressure. Was the system to do this not automated and controlled by a computer at this point in the cold war?
Of course they have to decompress. That’s why there are so many bars near the ports.
The pressure difference is simple. There are many systems on board that use high pressure air. They vent into the pressure hull. There’s also the added benefit (however small) of a little extra O2 from the compressed air being released into the atmosphere. The HPAC takes that air and puts it back into the air banks. That’s essentially all there is to it. As for automation, these machines (boats) are built for one, and only one purpose. They are NOT pleasure craft. What do you imagine would be the result in battle if the automation is damaged or destroyed? In those situations people are FAR more responsive and reliable. Simpler is better in battle.
Aren’t the newer subs more automated?
So the extra inch of mercury happens when the HPAC fails or is slow?
At least with modern methods, you can seal the electronics that do the automation with the sensors (redundant) and the actual thing it controls all in one water and shock protected housing. It’s going to be working long after all the crew near it are dead.
So I’m going to chase your logic down. . .
Have you not considered the fact that the Captain has protcols to consider atmospheric compression to the crew? Have you not considered the fact that the Captain of the boat may change depth to several hundred feet within moments due to the tactical situation? Everything changes . . .
SamuelA you have absoultely no grasp on the reality of things.
Tripler
I have a clue. And that’s based solely off of experience.
When I was on a sub we ran engineering drills three days a week, at least one of which (typically a reactor scram) would involve coming to periscope depth and running the diesel generator. In addition to reducing unnecessary drain on the ship’s battery running the diesel was an effective means of ventilating the ship and purging the atmosphere of any buildups (since we had freon-based air conditioning and smoking was pretty much allowed anywhere onboard in the 1980s we were frequently educated on nitrosamines).
If the diving officer or planesmen were under instruction (i.e., not yet very good at the job) it wasn’t unusual for the diesel intake snorkel to inadvertantly become submerged. There was an automatic valve that closes in that event, bit since the diesel is still running and exhausting through the snorkel (even if the snorkel is slightly submerged), you can believe that air pressure in the submarine wasn’t equal to surface pressure…
I’m not sure this is the case. This discussion of bathyscaphes (deep sea, but technically not submarines) refers to a huge pressure differential that the crew cabin must withstand. Discussions of the deep sea vehicle Alvin contain no references to decompression.
Here’s why, I think. You gain an atmosphere with every 10 meters (33 feet) of seawater. The Alvin has a test depth of 6500 meters. Compressing the cabin to 10 atmospheres would require a lot of decompression, as well as adjustment of the air mix to avoid nitrogen narcosis and oxygen poisoning. But it would relieve only 100 meters worth of pressure - not very much relative to the sort of depths the Alvin explores.
There are however, underwater habitats used for saturation diving, where Scuba divers spend days or even weeks at a given depth, without having to decompress every day.
Aircraft have these kinds of automated systems…how do you think single pilot fighters are even possible? What are you smoking?
What “experience” are you bringing to play here? Umm, come to think of it, so do ICBMs…
And if you read my post instead of banging your dick down noisily, you might have noticed that I mention the pressure would change if the sub were to suddenly change depth. I just thought it would level out over time, back to 1 atm, as the sub’s compressors and control systems correct the imbalance.
The sub’s depth has substantially zero to do with it. It seems that for whatever reason, various systems vent into the main crew space. As does the crew itself, which converts some fraction of food and water intake into gas.
The sub’s desigers, for whatever combo of reasons that make sense to professionals in the field, have decided there’s no particular reason to care +/- 1" of mercury how well the sub’s interior tracks the surface atmospheric pressure. After all, subs (boomers at least) surface once every couple of months. As long as the changes aren’t rapid enough to cause the crew any adverse symptoms, why bother to manage the tolerances any closer? Surface Schmurface.
Hell, over the course of three months submerged, the atmospheric pressure on the surface at any given spot goes through a delta of +/- 1/2" of mercury naturally just due to temperature and air mass / frontal changes.
The mere fact something could be more tightly controlled does not mean it should be more tightly controlled. especially not in a machine with severe space and reliability constraints.