Why are SSBNs so Quiet?

[Molon Labe]

Originally Posted by Neutrino 123

SSBN are reportedly very quiet, but why is this so? It seems to me in a basic analysis that they really shouldn’t be much quieter then SSNs of similar technology (though all sources say they are, so I would of course expect this to be true).

SSBNs have similar propulsion to SSNs, but they have a lower maximum speed. Approximately speaking, this implies similar machinery to the SSNs (this seems to be the case on cutaways I’ve seen, too…), but since the SSBNs are larger, they need more power to get the same speed, and thus, the machinery would generate more noise for the same effect. Presumably, this would be somewhat mitigated by additional quieting equipment. However, the storage space for the large missiles should limit the amount of space available for other things such as this, especially since the SSBNs usually have a larger crew and a fairly good torpedo armament, too.

In addition, the water noise flow that accounts for a portion of the BB noise (I am not sure how much, but this is something I would like to know…) would be significantly greater in the SSBNs.

…so, when considering the above, why are the SSBNs much quieter? Can they really fit enough quieting equipment to do this? If this is efficient, why not add similar equipment to the SSNs?

I tend to agree that SSBNs will be very close in noise level to SSNs of the same tech level. All the quieting technology that can go into the boomer would have gone into the fast attack. The main reason the SSBN is reputed to be impossible to locate is because, unlike the SSN, it doesn't go looking for trouble. It just finds a huge piece of ocean and crawls at very low speed. You won't find her unless you run her over.

An SSN, on the other hand, has to transit all over the place to complete its tasking, and will often have tasking in such areas that are have military significance.