The K-222 had an interesting design feature that made it possibly the world’s fastest submarine.
The K-222 was an extremely fast submarine. The Soviet Navy hoped that the K-222, a prototype and the sole example of the NATO-designated Papa-class, would be used to hunt down American or NATO surface groups through a combination of speed and stealth.
The submarine’s design was purposely restricted to incorporate new technologies and materials. This was a change in Russian submarine design, which traditionally favored slowly incorporating smaller improvements into new hulls, rather than radical redesigns. This new technology design requirement resulted in several pioneering features that made the K-222 one of the fastest submarines ever.
Nearly all submarines are constructed using steel alloys, which are lightweight and resistant to deformation—but K-222 was a bit more exotic. Rather than steel, designers opted to make the hull out of titanium. Titanium is lighter than steel, and better resists deforming, making it a useful metal for deep-sea submarine operations, where the weight of the ocean is crushing. There are a couple of drawbacks to building with titanium, however.
Titanium is orders of magnitude more expensive than steel—three to five times more expensive. Not only is the raw material pricey, it is also more expensive to manufacture. Because it is stronger than steel, purpose-built machinery is needed to manipulate the material. It’s also really hard to weld.
Unlike steel or aluminum, titanium can’t be welded in the open air. When hot, like during welding, titanium can easily absorb whatever elements are in the air, like oxygen, nitrogen, etc. These elements weaken the titanium, and result in a poor-quality weld.
In order to properly weld titanium, the Soviet Union had to build airtight warehouses that could be turned into a vacuum by pumping all the air out, then filled with argon—an inert gas that isn’t absorbed by hot titanium. Welders had to wear special space suit-like protective gear that had oxygen lines attached to allow them to breathe. It was an expensive process, but the results were interesting.
The K-222’s top speed was just over 51 miles, or about 82 kilometers, per hour—making the K-222 possibly the fastest submarine ever, and plenty fast to catch surface ships. There was a drawback though: the K-222 was really loud.
Though the K-222 was powered by two nuclear reactors, which are typically a quiet propulsion design, the sub’s propeller caused a great deal of cavitation—a phenomenon in which small bubbles form along the edge of a propeller and cause noise.
After an accident during routine maintenance, the K-222 was placed in reserve in 1988. In 2010, the K-222 was scrapped—with both nuclear reactors and fuel still onboard. The design had built the hull around the reactors, and apparently lacked a way to remove them. Some of the design sessions were incorporated into other Soviet designs, especially the Alfa-class, another fast, titanium-made submarine.
Caleb Larson holds a Master of Public Policy degree from the Willy Brandt School of Public Policy. He lives in Berlin and writes on U.S. and Russian foreign and defense policy, German politics, and culture.