Scott Elaurant
Well-Known Member
My understanding of the physics is that the risk of cavitation in a submarine declines as the water depth increases. At deep depths the water pressure is such that the air bubbles that cause cavitation less easily form on the propeller, hence no cavitation unless at a higher speed. Propeller design and devices like impellers also reduce the risk of cavitation. See this video by H I Sutton which explains how impellers work.
So if an SSN goes down below say 150 metres depth, it can scoot along at over 30 knots with only its engine and hydrodynamic noise. Of course that is still a lot noisier than at say 10 knots, so that SSN would still easily be heard at tactical ranges by an enemy sub.
The fastest cold war subs (Soviet Alphas) reportedly could do over 40 knots. These days quick SSNs can probably do 35 knots, the fastest SSKs can do 20-25 knots for a short sprint. I have never heard of any SSN that could do 50 knots.
The point is that the top speed of an SSN (much less than 50 knots) is NOT useful for tactical pursuit of an SSK. But it is very useful for the SSN escaping fire or rapidly redeploying to another location if in deep water. This is one reaspon why SSNs like deep water.
So if an SSN goes down below say 150 metres depth, it can scoot along at over 30 knots with only its engine and hydrodynamic noise. Of course that is still a lot noisier than at say 10 knots, so that SSN would still easily be heard at tactical ranges by an enemy sub.
The fastest cold war subs (Soviet Alphas) reportedly could do over 40 knots. These days quick SSNs can probably do 35 knots, the fastest SSKs can do 20-25 knots for a short sprint. I have never heard of any SSN that could do 50 knots.
The point is that the top speed of an SSN (much less than 50 knots) is NOT useful for tactical pursuit of an SSK. But it is very useful for the SSN escaping fire or rapidly redeploying to another location if in deep water. This is one reaspon why SSNs like deep water.
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