Why Do Submarines Come Up for Air?

Gone are the days when submarines relied solely on the surface for air. Modern submarines have sophisticated systems to produce oxygen from seawater, ensuring a secure and efficient underwater operation. This article delves into the techniques used in submarines to generate oxygen through electrolysis and how they manage carbon dioxide.

Oxygen Production for Submarines

One of the key challenges faced by submarines is maintaining a breathable atmosphere underwater. Oxygen is produced aboard submarines through the process of electrolysis, where seawater is electrically decomposed into its component parts: hydrogen and oxygen.

The electrolysis process involves running direct current (DC) electrical current through seawater, with sulfuric acid acting as a catalyst. This method effectively splits water molecules into hydrogen and oxygen. The hydrogen produced is highly flammable and is vented out of the submarine to prevent buildup, which could be dangerous. In contrast, the oxygen generated is channeled into the submarine's respiratory systems, ensuring crew members have a continuous supply of fresh air.

Handling Carbon Dioxide in Submarines

The primary issue with maintaining a breathable environment in submarines is the buildup of carbon dioxide (CO2). Unlike oxygen, CO2 can accumulate to hazardous levels, posing a serious threat to the crew's health and safety. To address this, submarines are equipped with CO2 scrubbers that continually remove CO2 from the air.

These scrubbers operate through a chemical process that involves reacting with CO2 and converting it into a less harmful substance. The process effectively filters out CO2, maintaining a safe and breathable atmosphere within the submarine.

Alternative Methods for Oxygen Supply

Submarines also have emergency oxygen tanks that can quickly increase the oxygen concentration in the air, should the electrolysis system fail. Additionally, submarines designed with nuclear propulsion use a unique method to manage their air supply. They have a process where seawater is broken down into hydrogen and oxygen, with the hydrogen being vented out and the oxygen being added to the air inside.

In the case of nuclear submarines, a snorkel mast can be raised to allow the submarine to run its auxiliary diesel engine at the surface. This process, though rare, helps in expelling CO2 and re-regenerating oxygen. However, this is not a common procedure as it sacrifices stealth for a short period of time.

Operational Practices on the Surface

While most of the time, submarines operate underwater, they do occasionally surface to use air compressors to replenish air banks, usually for high-pressure applications like ballast tank operations. During periods of near-surface operation, air compressors can be used to charge air tanks to ensure the submarine can submerge safely.

It's worth noting that submarines recycle the air inside before submerging, using filtration equipment to remove all solid debris. If needed, oxygen can be produced by electrolysis of seawater. This ensures a clean and breathable environment, both for the short-term and long-term operations of the submarine.

Conclusion

Submarines have developed advanced methods to ensure a reliable and safe air supply, primarily through the electrolysis of seawater. By continually processing seawater and efficiently managing CO2, these vessels can maintain a habitable environment for their crew without the need to frequently surface. Understanding these systems is crucial for anyone interested in the technology and operation of modern submarines.