air-independent propulsion

Air-independent propulsion (AIP) is a technology that allows submarines to operate underwater for longer periods without needing to surface for air. Traditionally, submarines used diesel engines on the surface to recharge batteries, which then powered electric motors for underwater travel. This meant they had to surface frequently, making them vulnerable to detection.12

The snorkel, introduced during World War II, allowed submarines to draw in air and expel exhaust gases while running their diesel engines just below the surface, enabling battery recharging without fully surfacing.2

Modern AIP systems, such as fuel cells that use stored hydrogen and oxygen to generate electricity, can allow some submarines to operate underwater at low speeds for up to a month. This significantly enhances their stealth and operational flexibility, making them effective for various naval roles. Nuclear-powered submarines, on the other hand, do not require air for power generation and can remain submerged for extended durations, offering a strategic advantage.13