Submarines, More Submarines

This is a very interesting link on the decision process in India for the next 6 AIP submarines they intend to buy. The Amur submarines at the bottom of the page caught my attention.

In November 2010 it was reported that Russia's Rosoboronexport will offer Amur-1650, its 4th generation diesel powered submarine against the Indian tender.

Amur-1650 Capabilities
Developed by Rubin Central Design Bureau for Marine Engineering, Amur-1650 has acoustic field rate that is many times lower than that of Project 877/636 diesel subs.

Armed with 6 torpedo tubes, the Amur-1650 can go to a depth of 300 meters. It is manned by a crew of 35 hand has an endurance of 45 days.

I believe the "acoustic field rate" being discussed here is being discused in the noise level of the Amur class submarine. According to Yang Xiushui, who might be the Chinese version of Norman Polmar, Project 877/636 (Kilo class) diesel subs noise is 105 decibels.

For comparison, ocean background noise is 90 decibels, and according to Yang Xiushui in the same article linked above, in his opinion the quietest submarine in the world is the Seawolf class with a reported noise level of 95 decibels.

I am not sure I believe the Amur-1650 is significantly quieter than the Kilo class, indeed perhaps only 2-3 decibels quieter at most. When it comes to submarine sounds, there are a number of ways that submarines can be made quieter, but as part of that discussion size does matter. These folks who talk about sound underwater and focus on propulsion really don't know what they are talking about - there are far more significant factors than type of propulsion plant a submarine has that determines the decibel level of a submarine.

In the case of the Kilo, its larger size allows for more technology and design characteristics that make the class remarkably quiet. The Amur-1650 is smaller than a Kilo, and while I believe it is probably quieter, I don't think the difference would be much - and one would have to factor the smaller payload capacity and shorter range the Amur has compared to the Kilo in this decision.

Personally, I think India should go for the French DCNS Scorpene MESMA submarines, because there are savings in the support costs when operating 12 of one type of submarine vs six versions of 2 different types of submarines. The way the Indian Navy buys small batches of different types of ships makes logistics and maintenance look really ugly for the Indian Navy.