How are modern submarines equipped to withstand high pressure underwater and to provide sufficient oxygen for the crew members?

Answer 1

Submarine Engineering to withstand Sea Pressure

The 2 major features of a submarine hull design that helps it withstand sea pressure at extreme depth is the material it's made of, and the design of the hull itself.

Spherical or round-shaped objects can withstand more pressure than other designs. This is why the Teardrop and Cigar shaped hulls of today were designed. The hull's material is also key - the more it can compress and expand, the less vulnerable it is to pressure. This is a problem with old Russian boats like the Alfa - they're made of Titanium. While it's very strong, it's not elastic, and every time it goes to deep depths it becomes more brittle with age.

Submarine Atmosphere Generation, Regeneration, Monitoring and Control

In 1975, the U.S. Naval Research Lab (NRL), developed and began deployment of the Central Atmosphere Monitor System (CAMS) on all U.S. Navy submarines. CAMS, and its successor on the Trident / Seawolf / Virginia class boats, is capable of monitoring key levels of toxic gases (CO, CO2, etc.) and will alert the crew if any level is in the danger range. CAMS readings are taken hourly aboard ship, and it's one of the most critical pieces of gear aboard a modern submarine.

There are several vital machines critical to maintaining the air environment for crew habitation aboard any submarine. Though it differs with the propulsion type (Nuclear or Diesel - Nuke's have more power generating capacity), in general they use the same methods.

The machines are:

1. Oxygen Generator (called the "Bomb") - Uses Electrolysis to separate Hydrogen and Oxygen atoms in distilled water. Hydrogen is bled back to sea as tiny bubbles, O2 is compressed in storage tanks outside the internal pressure hull, and released as needed into the crew areas to maintain a certain O2 level throughout the boat.

2. Carbon Dioxide Scrubber - Uses a chemical called Monoethanolamine to absorb CO2 from the air. The chemical is then heated, which releases the gas, which is then bled overboard. A powdered chemical called Lithium Hydroxide has also been used as a backup CO2 Adsorbent (sic) chemical in case the scrubber is inoperable.

3. Carbon Monoxide Burner - Absorbs CO uses a catalytic process to get rid of the gas.

4. Electrostatic Precipitators - positioned in the main Ventilation system, the ESP's remove particulates from the submarine environment - dust, smoke, etc.

5. Diesel Generator - All modern submarines use diesels for either primary or backup power generation, and also for emergency ventilation, either surfaced or at Periscope Depth using a Snorkel Mast.

6. Low-Pressure Blower - The LPB is essentially a big fan, capable of drawing in air from the surface via the Snorkel and rapidly ventilating the boat. Over time, scrubbed air gets pretty stale, and fresh air is a welcome change.

7. Main Induction Fans are responsible for circulating the air (cooled or heated as required by ocean water temperature outside) throughout the boat. the ventilation system can be configured to draw air in through the snorkel mast, or to just recirculate air. There has, however, been more than one occurrence of the main induction valve (which closes automatically when water hits it) on the snorkel mast failing, resulting in the main induction fans bringing in water at a very high rate.

A submarine environment, however clean air-wise, is still a toxic place to live and work. Most chemicals used to operate systems have their own carcinogens and vapors, e.g., diesel fuel and hydraulic fluid, and can lead to crew members developing lung problems over time.

All boats carry chemicals used to absorb toxic gases as well, and if necessary, the crew can breathe clean air from the Emergency Air Breathing (EAB) system, essentially a system of air manifolds with plugins that attach to full face breathing masks. These are often used during casualties / drills in which the boat hasn't had the time to reach PD yet, but the air is toxic enough to warrant EAB mask use. The system isn't without its problems though - in the '80's, the USS Bonefish, stricken by a Battery Well fire, lost its OOD, Radioman, Helm and Planesman who had remained onboard after the crew had been ordered topside to await rescue. Though they were wearing their EAB masks, they were found to have taken in hydrogen cyanide gas released through the burning of Otto Fuel, used in MK 48 torpedoes.