Key point: Unfortunately it sank on its first deployment.
From a Western perspective, Soviet engineers seemed to approach their Cold War submarine as if they were high-performance jet fighters meant to out-slug, out-run and out-dive their adversaries in a swirling dogfight. Soviet submarines were usually significantly faster than their American counterparts, could take more punishment thanks to their double-hulled designs, and could nearly always dive twice as deep at five hundred meters.
But the Soviet subs also had major weaknesses: they suffered horrifically high accident rates due to deficient radiation shielding and weak safety culture, and were much noisier. This allowed American subs to routinely detect and trail Soviet submarines without being detected in return. That acoustic stealth advantage is generally regarded as more useful in submarine warfare than the ability to execute dramatic maneuvers.
Nonetheless, in 1974 the Rubin design bureau finalized the design of a new submarine intended as a testbed for future fourth-generation submarines. In particular, the 685 sought to literally double the already considerable Soviet diving advantage.
The unique submarine, numbered K-278, was uniquely honored with the name Komsomolets, which more less meant “Communist boy scout.”
Komsomolets’s inner hull was built entirely out of titanium alloy 48T, an extremely expensive metal that is as strong as steel but considerably lighter. Welding together large sheets of titanium for a submarine hull is even more expensive, as it must be done in oxygen-voided buildings flooded with argon gas by workers wearing astronaut-like breathing suits.
The resulting Project 685 submarine, codenamed the “Mike-class” by NATO, was longer than a football field at 117 meters long and displaced 8,000 tons submerged. Its titanium hull allowed it to withstand and incredible 1,500 psi of pressure from the surrounding ocean. Advanced automated systems allowed the large submarine to be operated by a crew of just fifty-seven to sixty-four officers and seamen. Unusually, a unique escape pod was situated in her sail (conning tower). K-685’s single pressurized water reactor provided 190 megawatts of power, allowing a top speed of 30 knots—fast by Western standards, but typical for Soviet submarines.