Submarine Durability and Stealth: Modern Nuclear and Diesel-Electric Subs Explained

Submarines have long intrigued us with their ability to remain submerged for prolonged periods, rendering them almost invisible to their adversaries. This article explores how long modern US Navy submarines, particularly nuclear and diesel-electric models, can stay underwater without resurfacing.

Modern US Navy Submarines and their Capabilities

The endurance of modern US Navy submarines is remarkable. However, the limiting factor is almost always the food supply for the crew. Unlike early models, modern nuclear-powered submarines are equipped with systems that can generate oxygen and fresh water from seawater, allowing them to remain submerged for extended periods.

According to the public record, the longest continuous submergence by a submarine is 111 days, achieved by a UK fast attack submarine in 1982-1983. While this is impressive, the real limits for sustained underwater missions relate more to the crew's provisions than the technical capabilities of the sub.

Nuclear-Powered Submarines

Nuclear-powered submarines, known as SSNs (Attack Submarines) and SSBNs (Ballistic Missile Submarines), are designed to operate for extended durations, often for years without surfacing. The USS Ohio Class SSBN, for example, is capable of deploying for up to 30 years before requiring refueling. Despite this, the crew must still resurface periodically for maintenance, crew changes, and supplies.

USS Ohio Class SSBN

The USS Ohio Class SSBN, also known as "boomers," are the primary nuclear-powered ballistic missile submarines of the US Navy. These submarines are capable of deploying for up to 3 months under a single crew (Blue Crew and Gold Crew), ensuring continuous deterrence at sea. These submarines are equipped with advanced nuclear reactors that provide nearly uninterrupted power, enabling them to stay submerged for up to 180 days before needing resupply.

The Ohio Class SSBN has specific characteristics that distinguish it from other classes:

Displacement: 16,764 tonnes surfaced, 18,750 tonnes submerged Length: 560 ft (170 m) Beam: 42 ft (13 m) Draft: 35.5 ft (10.8 m) Propulsion: 1× S8G PWR nuclear reactor, 2× geared turbines, 1× Fairbanks Morse auxiliary diesel, 1 shaft with a seven-bladed screw Speed: 12 knots surfaced, 20 knots officially reported submerged, 25 knots reportedly submerged RANGE: Limited only by food supplies

Diesel-Electric Submarines

Compared to their nuclear counterparts, diesel-electric submarines (DDGs) have limited underwater endurance. However, advancements in technology have significantly extended their operational ranges. A typical diesel-electric submarine can usually stay submerged for up to 24 hours, while some can remain underwater for up to 12 hours with water and air purifying systems.

For example, the Los Angeles Class SSN is known for its robust capabilities:

Boats in Service: 26 Displacement: 6,082 tonnes surfaced, 6,927 tonnes submerged Length: 362 ft (110 m) Beam: 33 ft (10 m) Draft: 31 ft 9.4 m Propulsion: 1× S6G nuclear reactor, 2× steam turbines, 1 shaft Speed: 20 knots surfaced, over 25 knots submerged Range: 120 days before replenishment required

Challenges and Innovations

The limitations of current technology aside, innovations are being explored to further extend the endurance of submarines. Water-based food production, such as 3D-printed sustenance, is being studied to reduce the need for resupply missions. This would enable submarines to stay submerged for extended periods, potentially even decades.

Furthermore, the US Navy is developing methods for at-sea replenishment. This could involve using helicopters or even specialized aircraft like the V-22 Osprey to deliver supplies, ensuring that submarines can remain operational for as long as necessary.

Conclusion

Modern submarines can remain submerged for extended periods, with some capable of staying underwater for up to 30 years. However, the key limiting factor remains the food supply for the crew and the need for periodic resupply. Advances in technology and ongoing research are continually pushing the boundaries of submarine capabilities, making them formidable stealth assets for extended periods at sea.