What I'd asked for was a nuclear submarine propeller, better known in the Navy as a screw. It is so secret that when a sub comes in from patrol its propeller is shrouded with a large covering, and if a sub is drydocked for any length of time, it is commonly removed and stored away from the ship for servicing and prying eyes. It is what drives a submarine quickly and quietly through the water, and it is absolutely critical to a submarine's stealth. It is an extremely high-tech piece of equipment, resulting from extensive Navy research and development, and until recently our propeller technology exceeded the Soviet Union's by a considerable margin. As a result of this and other factors, Soviet submarines of the Cold War were noisier, and therefore easier to detect than our own. Within the context of national security and defense, as well as our nuclear deterrence policy, it is easy to see why propeller research and design have been so carefully guarded. The propellers of USS Nautilus, the first nuclear submarine, are an exception. Essentially World War II submarine propellers, they—along with the rest of the sub—are on display at the Submarine Force Museum in Groton, Connecticut, near where she was built in 1955.
But something happened to change all that. Back in the mid-1980s, the Japanese company Toshiba sold propeller milling machinery to the Soviets through the Norwegian Kongsberg firm; this and other submarine intelligence furnished by the Walker spy ring resulted in significantly quieter Soviet subs by the later part of the decade. As writer Neal Stevens wrote about the Akula-class Soviet boats, "The combined results generated a steep drop in broadband acoustic noise profiles."
