Why Modern Submarines Have Round Noses?

[Music] why are submarines not shaped like fish after all billions of years of evolution has probably resulted in fish having the perfect shape or has it we're specifically talking about the nose of the submarine or more correctly the submarine's bow why is it round and not pointy like fish looking at various classes of modern submarines compared to various species of fish it's clear that fish have pointy noses while submarines have rounded bows but the reason is not what you think prior to the cold war most submarines had a pointy bow kinda and that's because older submarines were more like ships as they spent more time on the surface than underwater especially when traveling long distances and here's why older submarines could not stay submerged for a long period of time as they needed fresh air intake for their diesel engines to work and once submerged submarines were running on batteries which powered electric motors the thing is the batteries wouldn't last very long just for reference modern nuclear powered submarines can stay submerged for about 90 days and that limitation is mostly due to limited food supplies theoretically a nuclear submarine can run for about 20 years without the need to refuel conversely older submarines could only stay submerged for about 12 hours or so with late war german designs achieving the capability of sync submerged for a few days while traveling at a speed of about 5 knots and that's another thing submarines were very slow underwater for instance an american below class submarine had a submerged top speed of just under 9 knots while it could go in excess of 20 knots when traveling on the surface but modern submarines have top speeds in excess of 30 knots while traveling underwater this is why traveling underwater for long distances for older submarines was just not feasible and that's why they would move to the surface just like ships when traveling long distances submerging was only for attack or escape runs for this reason older submarines had ship-shaped bows as they functioned like a ship for the most part when these older submarines were designed the focus was always on the surface performance and not on the submerged performance but then came nuclear power which made submerged performance a thing and as often happens submarine designers had to learn the hard way in the early 1950s the u.s navy was building two unique submarines which proved to be game changers uss nautilus and uss albacore launched in 1954 uss nautilus was the first nuclear-powered submarine in the world underway on nuclear power meant that from then on submarines could travel long distances underwater both speed and endurance were greatly increased however while nautilus did not have a true ship-shaped bow it had a semi-pointed bell which turned out to be a huge problem the bow was shaped around its ultra-modern sonars however these sonars were more or less useless as nautilus was a very noisy submarine whenever the boat traveled at faster than seven knots her sonars would be deafened by the noise of the submarine itself which rendered the sonars unusable this issue was traced back to serious design flaws in her bow and sail that resulted in extreme vibrations at high speeds by the time nautilus had reached end of life traveling at just four knots would cause enough noise to deafen the sonar clearly there was some design work to be done but that design work was already underway it just happened concurrently as nautilus was being built the diesel-powered uss albacore was a research submarine whose design was derived from extensive hydrodynamic and wind tunnel testing it was the first attempt to design a submarine with a focus on submerged performance as compared to surface performance one of the goals was to minimize submerged resistance albacore's new hull shape was known as a teardrop hull launched in 1953 uss albacore underwent several overhauls where design elements were modified and tested during early sea trials it was found out that she could operate at maximum speed at half shaft power compared to the older guppy type submarines albacore's design proved to be a revolutionary compared to the older ship shaped designs because not only was she much faster she was also more maneuverable her maximum speed was in excess of 25 knots and even though albacore was diesel-powered she was much quieter than nautilus albacore's hull design was eventually implemented on the skipjack class the first class of american nuclear attack submarines in 1959 and pretty much an all-modern american submarine since but there was a downside to all this she was not very stable on the surface around the same time the soviet union also commissioned its first nuclear submarine the k3 leninski comsamol which had a round bow that proved to be much more efficient and spacious compared to older ship-based bows so what is it about the round bow that makes it such a good design choice and why not have a fish-shaped bow the first thing to understand is that during dives submarines are under extreme water pressure modern submarines can dive much deeper than before with most being able to dive over a thousand feet with a record of 3350 feet to withstand such extreme pressures the geometry of the boat makes a huge difference generally the curvier the better and if you ask me that goes beyond submarines [Music] if you've heard of the de havilland comet you'd know that that airplane had problems with square windows generating three times the stress around the fuselage joints after one fatal disaster all future airplanes switch to windows with round corners to eliminate stress concentration round shaped things tend to be stronger than angular frames similar logic applies to submarines with most of the body being cylindrical with a curved bow modern submarines typically have two hulls a pressure hall and a light hole the pressure hall provides an atmospheric pressure for the crew and other devices that need to function at a specific pressure humidity and temperature the light hull provides the space for equipment that can handle the water pressure at depth such as ballast tanks sonars and torpedo tubes the bow of most submarines is part of the light hull since it gives the submarine as shaped for the best possible performance another thing to consider is how noisy submarines can be as the water flows around the submarine the turbulent pressure fluctuation in the flow radiates a noise known as flow noise as was learned from uss nautilus the shape of the bowel makes a big difference in the amount of flow noise generated if there's too much noise it can render the boats sonar unusable moreover it would be much easier to detect a noisy submarine which in combat situations is counterproductive to say the least generally speaking curvier bows produce less drag which results in less flow noise with that said flow noise is also affected by the positioning of the diving planes the size of the sail and the overall shape of the submarine as a submarine travels submerged it encounters resistance from the water that is ahead even though many modern submarines are nuclear power there is still a cap on the amount of power they can generate so minimizing submerged resistance is a key aspect of submarine performance the amount of curvature in the bow impacts resistance and certain shapes will produce less resistance versus others but the question is would a fish-like bow produce less resistance compared to the round-shaped bow of the modern submarines in other words which one got it right millions of years of evolution or a couple of hundred years of submarine design a paper in the journal of scientific and engineering research analyzed the effects of the various bowel shapes on the submerged resistance one of the boughs analyzed was the ogive shaped bowel which in our eyes resembles a fish other bow shapes analyzed included ship-shaped bow elliptical conic and hemispherical not surprisingly the ship-shaped bow has pretty high resistance as it was not designed for underwater performance the hemispherical bow has the highest resistance while fish-shaped and conic boughs have the lowest resistance elliptical and conic elliptical sit in the middle of the spectrum so why is it that most modern submarines don't have fishy bowels or conicals but instead have bows that vary from elliptical to hemispherical clearly there is something else going on under the hood besides minimizing flow noise and submerged resistance while the reduction of resistance and flow noise are important considerations for submarine design the shape of the bow is also dependent on the internal architecture of the boat besides the ballast tanks the bow of the submarine usually features a giant spherical sonar and the torpedo tubes neither of which would fit in a conical or fish-shaped bow passive sonar occupies a huge volume of space inside the bow of the submarine however the sonar is critical for submarine navigation as it's the eyes and ears of the boat having a smaller sonar fitted into a fish-shaped bow simply won't cut it in fact navies would often try to fit the largest sonar possible into the submarine for instance with uss tullibee the u.s navy removed the torpedo tubes from the bow of the boat and placed them on the sides this allowed for more space to install a long-range spherical sonar which enabled anti-submarine hunter-killer missions if you compare the hull shapes of uss tulibi and uss thresher tullibee was more on the hemispherical side compared to the more elongated elliptical bow of the thresher point being that sonars and thus bow volume was a bigger priority compared to the overall underwater performance of the boat graphing the volume coefficients of various bow types demonstrates that conic shaped bows have the lowest volume while the hemispherical boughs have the highest volume with elliptical bowels sitting somewhere in the middle combining the adequate interior volume on one hand with a reasonable submerged performance on the other hand explains why most modern submarines have elliptical shaped bows and not fishbows but if we go one step further and combine the resistance and volume coefficients we'd get a hydro-volume efficiency coefficient when graphing the bow types it's clear that the elliptical bows are as efficient as the fish bells despite this fish bows are not a common practice due to many difficulties in internal arrangements of torpedo tubes and sonar equipment but what about astute class submarines they don't have an elliptical shaped bow they instead have a hybrid conic elliptical valve the royal navy claims that this hybrid bow is a compromise between hydrodynamic efficiency and cost while elliptical boughs would provide better performance it is more costly to produce those curved plates out of a thick high-strength steel so the royal navy chose a less expensive alternative by using thinner and more easily shaped steel sections that can be welded to a pressure hull while this design has a negative effect on performance it does provide additional space and is much cheaper so back to the opening question why are submarines not shaped like fish lucky for fish that don't need to carry sonars except for the ones that do [Music]

Channel: Not What You Think

Views: 3,767,701

Keywords: not what you think, Pressure Hull, Light Hull, Submarine Shape, Flow Noise, Submerged Resistance, US Military, US Navy, Nuclear Submarines, USS Nautilus, USS Thresher, USS Albacore, Astute-Class

Id: exm65Y_LZxw

Length: 12min 54sec (774 seconds)

Published: Fri Feb 25 2022