The Virginia-class, also known as the SSN-774-class, is a class of nuclear-powered fast attack submarines (hull classification symbol SSN) in service with the United States Navy. The submarines are designed for a broad spectrum of open-ocean and littoral missions. They were conceived as a less expensive alternative to the Seawolf-class attack submarines, designed during the Cold War era, and they are planned to replace the older of the Los Angeles-class submarines, twenty of which have already been decommissioned (from a total of 62 built). The class was developed under the codename Centurion, renamed to NSSN (New SSN) later on.^[7] The "Centurion Study" was initiated in February 1991.^[8] Virginia-class submarines will be acquired through 2043, and are expected to remain in service past 2060.^[9]