Soviet engineers developed a unique class of submarines called "Lira" (Project 705, NATO codification: Alfa), which the United States could not replicate. This is according to military expert Brandon J. Weichert in the article "The Soviet Union Built a Titanium Submarine. Why Didn't America?"
During the Cold War, many new submarine projects were created by both US designers and their rivals in the USSR. But the Soviet Navy had more interesting projects, some of which became iconic.
In the US, "there was always concern about new Soviet submarines that could threaten NATO ships, so the Americans often tried to replicate what they were doing in the USSR." However, the US Navy was unable to replicate the innovative development—a submarine with a titanium hull.
The problem is that titanium was hard to come by. That's one of the reasons why the US Navy never tried to develop an Alfa-class submarine. Welding a titanium hull is a technically complex process, which leads to increased production costs.
At the same time, titanium has many advantages: it is stronger and lighter than steel, and less susceptible to corrosion. Submarines made of this material can withstand high pressure, which allows them to dive to greater depths.
These submarines could chase any ship and were stealthy. Thanks to the lighter hull, they had high maneuverability, which in theory meant that they had a better chance of evading NATO's impressive arsenal of anti-submarine weapons.
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