In summary, the Seawolf cannot reach 45 knots, as is sometimes claimed. Plugging in the numbers, we get U=18.16 ms -1 or 35.3 knots. Specific numbers are harder to get for the Seawolf, but I will use a 1963 Electric Boat 85% estimate for pumpjet efficiency and the generally accepted public figure for turbine power. Plugging in the numbers, we get K=0.0108. Rearranging our power equation to solve for K, it becomes, Since 1 m 3 of seawater weighs 1,025 kg and a long ton weighs 1,019 kg, let's say tonnage = displacement in cubic meters. The Permit-class submarine has a similar length-to-beam ratio, and had the following characteristics with a 7-bladed screw (effective power based on Electric Boat estimates of Lafayette-class SSBN with 7-bladed screw), Since we don't have a model basin at our disposal, let's pick a submarine with a similar form to the Seawolf that we know the power and top speed. At top speed, drag and power will be equal so,įirst we must determine K. Since work is force times distance, and power is work over time, power is force times velocity. Where K is a drag coefficient lumping together C, ρ, and the trickery we did with the volume. Taking the cube root of the volume (displacement) gives a characteristic length, and squaring that gives a characteristic area. For a submarine, we can rewrite this in terms of the displacement. Where D is the force of drag, C is the drag coefficient (determined empirically from tests), ρ is the density of seawater, A is the cross-sectional area, and U is velocity. Some theory first, taken from Concepts in Submarine Design by Burcher and Rydill. Of course, this only means that she was faster than the Skipjack or Los Angeles, both of which had top speeds of about 33 knots. The whole "Seawolf can do 45 knots" myth probably started when an admiral said that she had gone faster than any American nuclear submarine had before. Those links are on my reddit profile if you want them, although it's nothing a few minutes of googling and libgen can't find. Sadly, I haven't done much physics, so I can't really do the "back of the enveloppe" computations often mentioned myself. I have found a few hydrodynamics papers explaining why required power goes up with the cube of the speed, or why continuously curved hulls are theoritically better (although harder to manufacture / design) but not much on how to provide an estimate for speed. Obviously this is all pretty sensitive, but I reiterate, I'm only interested in estimates based on public data for displacement / hull shape / shaft horse power. Sadly, I cannot find those comment again, and IIRC it only mentioned the computation being done, but not how. Obviously, it's very rough, but it helped him to debunk the 60 knots Ohios and stuff like that, using a best case scenario for power, and public data for displacement. I remember /u/Vepr157 discussing this on reddit, on how they could provide an upper bound on reactor power using the size of the hull section housing the reactor, and public data on the power density of PWR reactors. īut then I wondered how those public estimate using OSINT data are actually made. I feel like that's unlikely, because the alfas barely did more than 43 with around the same power, for half the displacement / A much smaller wetted surface / (i'm getting more speculative / unsure here) a more efficient hull / sail form (blended sail, body of revolution hull form). Someone on reddit is telling me that SSN21 could do more than 47 knots. I don't own the book, so I can't check, but I wonder how this estimation was computed. The source is Polmar, Cold War submarines, so that's quite trustworthy IMO. The wikipedia article for the Los Angeles class mentions that unclassified estimate of the LA class top speed are around 30 to 33 knots. I am posting this as suggested by /u/Vepr157, so that everybody can see this, hopefully it will be interesting. USS Razorback - SS 394 - Little Rock AR.Veteran's Crisis Lineġ-80 or text "start" to 741-741 Museum Submarines If you don't have any documents you can request a board to verify knowledge.a photo of you in uniform showing pins (Dolphins).Official awards showing your qualification.Message your verification info to The Chief Why Submarines are called boats and not called ships - /u/Vepr157 We are the subreddit dedicated to every machine under the water. "A billion dollar house, and the roof leaks.” - Submarine Mechanic Proverb
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