The Project 661 Anchar (NATO: Papa-class) SSGN was a Soviet nuclear-powered cruise missile submarine designed as an experimental high-speed attack platform. Constructed with a titanium hull, it was the fastest submarine ever built, reaching speeds of 44.7 knots (83 km/h) during trials.Armed with P-70 Ametist (SS-N-7 Starbright) cruise missiles, the Papa-class was intended as a prototype for the more advanced Oscar-class SSGNs. However, its high cost, excessive noise levels, and complex maintenance requirements led to only a single unit, K-222, being built.Commissioned in 1969, it served primarily as a technology demonstrator, influencing future Soviet submarine designs. It was eventually decommissioned in the 1980s, but its speed record remains unbeaten among submarines.