Submarines Spend Months Submerged - Where Do They Get Oxygen ...

Nuclear submarines can spend months without emerging to the surface. This poses a lot of problems to the members of the crews. For example, where do you get food? Where does the drinking water come from? And how do you get air when there is half of kilometre worth of water above your head?

We will answer these questions within this article.

Air, of course, is very important, but let’s start with water problems. Although sea water is too salty to be consumed, it works perfectly well in the toilet.  You do your business, flush and the waste is collected in a special tank somewhere in the bottom of the pressure vessel. Once it’s full, the waste is ejected using compressed air. Yes, the sailor poop goes straight into the ocean.

USS Annapolis – submarines like this one can spend months without emerging to the surface. Image credit: US Department of Defense photo by Tiffini M. Jones, Wikimedia)

However, you don’t want to shower and cook using salt water, which means it has to be purified before consumption. In fact, nuclear reactors are also using purified water. All particles and salt are removed using a process called reverse osmosis, but other methods can be used as well.

In some cases water may be distilled or it can be made in special reactors that break down CO2 and marry that remaining oxygen with hydrogen to produce water.

You can spend days without water, but you would die within minutes without oxygen. Atmosphere inside submarines is very carefully monitored and controlled. Submarines are huge closed tubes, which do not have very good air circulation. There are no plants to recycle CO2 either, so everything has to be done using some impressive technologies.

How do submarines get air?

Most people who first learn of submarines probably wonder just how do submarines get air? Well, in order to keep the air they have to begin with breathable three important steps must be followed:

• As oxygen is consumed it must be replenished at the same rate to avoid the percentage within the air falling.
• The percentage of carbon dioxide within the air cannot be allowed to rise as the air will start to become thinner.
• Moisture that is exhaled must be removed.

Submarines get oxygen, air, from a few ways in most cases. The first being from an oxygen generator which can form oxygen from the electrolysis of water.

Pressurized tanks are also common on submarines as a way of getting air, as well as, oxygen canisters which release oxygen courtesy of a very hot chemical reaction.

How does a submarine make oxygen?

Oxygen in submarines is produced by putting sea water through a process of electrolysis. Submarines typically have a couple of big oxygen tanks as well, used to quickly raise oxygen concentration if the system fails. Actually, normally oxygen concentration is slightly lower in the submarine than it would be on the land. This allows for reducing the risk of spreading fires. There are many different sensors around the submarine, monitoring the concentration of oxygen and carbon dioxide, which has to be removed.

Interior of the S-189 submarine – smells are something you had to get used to. Image credit: Benjamín Núñez González via Wikimedia (CC BY-SA 4.0)

CO2 removal is not an easy business either. Amines are used – these chemicals absorb CO2 when they are cold and release it once they are heated up. Waste CO2 is released into the sea whenever it’s possible. However, these amines do have an unpleasant smell, but people who served in submarines say that you can get used to that smell.

Actually, you have to get used to a variety of different smells. Living compartments are tight and not that well ventilated. You can smell food being prepared, hydraulic oil, amines, trash and so on. And you can’t open a window, because there aren’t any.