Submarines operate for extended periods underwater, often without access to the surface. To sustain their crews, they must provide a continuous supply of breathable air—primarily oxygen—while removing harmful gases such as carbon dioxide. Unlike surface ships, submarines cannot rely on external ventilation, so they use a combination of onboard oxygen generation systems, chemical processes, and storage methods to maintain atmospheric conditions.
Oxygen Requirements in Submarines
- A typical human consumes about 0.84 kg (1.9 lbs) of oxygen per day.
- Modern nuclear submarines carry over 100–150 crew members, meaning several hundred kilograms of oxygen must be produced or stored for long-term missions.
- Oxygen levels must be maintained at roughly 21% concentration, similar to surface air. Too little oxygen leads to hypoxia, while too much can increase fire risk.
Methods of Oxygen Production
1. Electrolysis of Water (Primary Method)
- Nuclear and large conventional submarines generate oxygen using electrolytic oxygen generators.
- Process:
- Seawater is purified into fresh water.
- An electric current splits water molecules into hydrogen and oxygen.
- Oxygen is released into the submarine’s atmosphere.
- Hydrogen is vented overboard.
- This method provides a continuous and renewable oxygen supply, powered by the submarine’s nuclear reactor or batteries.
2. Compressed Oxygen Tanks
- Submarines carry high-pressure oxygen cylinders as a backup.
- These tanks can be used to quickly replenish oxygen levels in emergencies or when demand exceeds generation capacity.
- Stored oxygen must be carefully regulated to avoid over-oxygenation and fire hazards.
3. Chemical Oxygen Generators (“Chlorate Candles”)
- Emergency devices that release oxygen when ignited.
- Typically composed of sodium chlorate (NaClO₃) mixed with an iron powder ignition source.
- When burned, they decompose to produce oxygen and heat.
- These are used as a last resort in case of generator failure.
Air Purification Systems
In addition to oxygen generation, submarines must maintain air quality:
- Carbon Dioxide Scrubbing
- CO₂ buildup is toxic even at low concentrations.
- Submarines use lithium hydroxide canisters or regenerative scrubbers to absorb CO₂ from the atmosphere.
- Carbon Monoxide and Trace Gas Removal
- Catalytic burners break down carbon monoxide and hydrocarbons.
- Activated charcoal filters remove odors and contaminants.
- Humidity Control
- Moisture is regulated to prevent condensation and mold growth.
Nuclear vs. Diesel Submarines
- Nuclear Submarines
- Virtually unlimited energy supply for electrolysis.
- Can remain submerged for months at a time, limited primarily by food supplies.
- Diesel-Electric Submarines
- Must surface or snorkel periodically to run diesel engines and refresh air.
- Still carry oxygen generation systems for extended submerged operations, but endurance is shorter than nuclear vessels.
Safety Considerations
- Fire Risk: Excessive oxygen levels increase combustibility. Submarines carefully regulate oxygen concentration.
- Explosion Risk: Compressed oxygen tanks must be stored securely to prevent catastrophic ruptures.
- Redundancy: Multiple independent oxygen systems (electrolysis, tanks, chemical generators) ensure crew survival even if one system fails.
Historical Context
- Early submarines (19th–early 20th century) relied on surface ventilation and compressed oxygen cylinders.
- By World War II, chemical oxygen candles and soda lime CO₂ scrubbers were standard.
- Modern nuclear submarines developed advanced electrolysis systems, allowing indefinite submersion limited only by crew endurance and food supplies.
Summary
Submarines make oxygen primarily through electrolysis of water, supported by compressed oxygen tanks and chemical oxygen generators for backup. These systems, combined with air purification and CO₂ scrubbing technologies, create a closed life-support environment that allows submarines to operate underwater for months at a time. Oxygen generation is one of the most vital technologies enabling the strategic endurance and stealth of modern submarine fleets.
Last Updated on 5 hours by pinc