[TLAM Strike]

Originally Posted by Bubblehead Nuke

To be quite honest here, the reason they are quieter is due to the MASSIVE improvements in pump impeller designs gained when Toshiba sold them all the fancy metal milling machines. The predominate noise produced by a nuclear sub is not from the screw, but from the gear used to run and support the reactor plant.

While they got the quieter pump impellers, they still have the lousy screw designs that were optimized for speed and acceleration rather than stealth. At a slow enough speed, even these screws were pretty quiet. Thus you have a quiet boat at slow stalking speeds. As soon as they start cranking up the RPM'S they are just as loud as ever. Their reactor plants also have some fundemental differences in operation from the American boats that showed a greater noise impact from the improved impeller construction.

Why did they design the screws for speed and acceleration you ask? The plants were noisy as heck so why not make it a better performer. A quieter screw had no purpose. Thus they were better equipped to runout maneuver a torpedo. If you can get up to top speed fast enough, you could get out of the aquisition cone of the incoming torpedo.

Also, there was a funamentel difference in MISSION between US and the Soviet subs. Ours was a forward offense mission while theirs was more home water defense. A boat had to be able to move QUICKLY to get into an intecept position based on external data. Thier boats works as teams with surface and/or air assets while our boats operated in a more independant ops mode.

Well better screws were a part of it but not as you think, the screws of the 3rd Gen Russian subs (Typhoon, Oscar, Akula, Sierra, Mike) were designed before that, the Japanese and Norwegian “scandals” simply allowed the Russians to build their own designs of better quality and faster.

When I talked about quieting I was thinking of 1st Gen subs. It might be hard to believe but the early Russian subs were stealthy than ours at low speeds thanks to anechoic tiles on that big double hull of theirs. The US 1st gens nucs were noisier than the WWII fleet boats! Nautilus was renowned for its self noise over 8 knots, in fact she was a test bed for experiments relating to that. I know Bill our Master of Defense has shared several stories about their time as a test bed sub.

Back to Russia in the 80's reactors were also quieted the OK-650a was capable of natural circulation for cooling at low speeds. The Sierras used this reactor, the Akula's have a similar plant the OK-650b same as the Oscar. (The Typhoon had the OK-650, the Mike the OK-650b-3) Latter Russian boats also have “Active Noise Cancellation” systems which I've never heard of US boats having.