1945 – Britain’s Astute-class nuclear-powered attack submarine is so quiet that sonar operators have mistaken its acoustic signature for a baby dolphin or ambient ocean background noise. Engineered around raft-mounted machinery, anechoic tiles, and a pump-jet propulsion system, the boat runs on a Rolls-Royce PWR2 reactor that lasts the submarine’s entire operational life and reaches 30+ knots submerged.