Since this isn't classified or need to know information, i'll tell you the main reason they hide propellers on submarines. If you can measure the general size, shape, and the number of fins on the screw; you can calculate the sonar signature of the screw. You then add this to your shipboard sonar library to use in helping you identify submarines and ships. It's as simple as that. You wouldn't believe how much time is spent on recording and cataloging sonar signatures.
@@dspates51 Sir,why those sub designer refuse to imitate the way squid travel in water?..I think the jet engine idea was derived from the squid swimming system,thus the phase.out of propeller type plane engine in favor of the jet engine. What happen to the plan to duplicate the design of fish tails,fins, etc in their swimming method?..I think naval engineers had already figure.out how fast swimmer fish do their craft via their amazing tail...Is the fish propulsion system hard to duplicate?..
I thought it was more for design and concepts because a lot of technology and design goes into the blades to help stop cavitations that destroy propellers I didn't realize you could figure out the sonar signature that's truly impressive
@@Loquacious_Jackson Harmonics are integer multiples of the the base frequency. 2, 3, 4, 5, 6 would be the harmonics below 7, and 7 is not divisible by any of them. Would work with 5 too, or 11 - but that's a lot of blades.
Primes are amazing, often come up with very simple applications. In this case I'd assume harmonic waves would cause strengthening of those waves (=constructive interferecens), like pushing a child on a swing at regular intervals would increase kid's speed, whereas pulses with irregular intervals (which you get with primes) would cause non-harmonic waves, causing destructive interference instead
Nobody can knock you for staying on the safe side of the line. It’s understandable that your knowledge also contains official reasoning, instead of just intelligent analysis that can point out multiple characteristics without knowing how important each was in the official decision process
This is next level! Thank you! I was so sick and tired of the typical "content creators", who, much like cheap copies of a Discovery Channel lay the focus on "exciting" and neglected "interesting" and "well researched". With your content, it is exactly the opposite. Highly knowledgeable individual giving an unscripted, in-depth talk with "simple" imagery. Well worth the wait between videos. For me, right up there with Greg's channel on aircraft and engines.
Agreed. One thing I can't stand, is the overly dramatic narration and focus on superlative specs and number of swimming pools, football fields, or elephants. You never really learn much about the core technology and it's just meant to impress.
@@wyskass861 Science is / SHOULD BE boring to listen to, because the exciting bits are the actual facts and not the "dress" in which it is presented. This focus on flashy (and often enough EMOTIONAL) narration also "hypnotises" people into STOPPING TO THINK and there is nothing better than GLOBAL WARMING to showcase it, because the ONLY SOLUTION - thanks to the "green fanatics" - is "reducing CO2", but there are at least TWO OTHERS (and a powerful reason why "managing CO2" WONT WORK): 1. "the tragedy of the commons" explains why reducing CO2 will NEVER work ... and even the most willing of countries - my country of Germany - have broken their promised reduction goals, because they simply cant bring themselves to NOT introduce the 5G phone standard which will require more power than the previous one 2. a few years back there was this volcanic eruption on Iceland, which poured loads of ash into the atmosphere, blocking air traffic over the northern Atlantic Ocean for months, but a year later some scientists speculated that it might have lowered the average temperature by 1° 3. a "solar shield in space" would reduce heat incoming from the sun, so it would even help if THE SUN is causing the increase (which we simply dont know, which is another reason why "reducing CO2" possibly wont do anything). With Elon Musk's improvements in "rocket science" (or rather: application), it should be possible to a) transport a large amount of satellites into space, which provide shade for the earth AND to haul a big asteroid from the asteroid belt into a stationary position between sun and earth. Nobody is "thinking outside the box" like this, because the media like their sensationalised one-track-thinking ... oh and "electric cars" is another one of those topics.
I have a true story to tell you. Many years ago, a professor of Mechanical Engineering at the University of Hawaii, Dr. Karl Ihrig, had engineering students in his classes that were in the US Navy. He was invited to look at some nuclear submarines at Pearl Harbor as his student’s guest. In those days, the submarine screw was exposed. He looked at it and exclaimed “Wow, you can actually do XXX knots top speed?” His students were startled & asked how he did that because his figure was accurate, though classified. He said from the size & shape of the propellor, he did the calculation by eye & in his head. This stunned his students & they reported this up the chain of command. After that, the Navy started covering the propellers so that it could not be photographed, especially by satellite. Dr. Ihrig also help design the underwater BART tunnel in San Francisco in such a way that pressure would remain relatively constant (despite the rapid change in depth) by the movement of the train, making pressurized passenger cabins unneeded. It was his idea. There still is an engineering company that bears his name in San Francisco, though he sold it years ago. He has since passed away.
12:54 The erosion seen on the edges of the props is due to erosion from cavitating flow. Impellers used in hydro turbines (as used to generate power in dams) suffer from the same issue.
Current STS here. Not much I can comment on without having to check classifications, but decent video. Some things to think about from an engineering perspective: Slower screws (lower TPK) require bigger shafts due to the high torque. This is why diesel boats don't really employ any crazy super low TPK screw designs, they don't go very fast in the first place and the extra shaft diameter would just rob them of valuable space. Also, mission matters. Pump jets only work well in one direction. Boats that need to loiter/make very controlled movements dont use them often because reverse thrust is extremely inefficient through a pumpjet.
@@HISuttonCovertShores Seawolf class submarines have propulsors. People often use the term interchangeably with pumpjet but it isn't quite the same. Either way, they are very fast but not great at slowing down.
@@Maverickib On a T boat on patrol in the MIZ (Marginal Ice Zone) we managed to operate for weeks at an average of one knot while maintaining our heading. We had what was in reality a stopped trim. It was supposed that an SSN was deemed too big to achieve a stopped trim., NOT SO, a stopped trim can be achieved, you just have to develop the techniques and put that into practice. UK SSN crews have that ability, the are VERY highly trained.
@@petewilliams.1122 Well yeah, SSBNs hover all the time. Never said boats can't do it. Propulsors just make it more difficult. Hovering (stopped trim) is more a function of expertly controlling ballast than anything. Seawolf has a propulsor and we can still do it (I've been in the MIZ as well), we just have to be very careful when it comes to increasing speed because the propulsor makes it difficult to slow down.
Another video! Great! I love the 'chat' format to be honest-- it's very well delivered. I like the descriptions of the remarkable and interesting features of these awesome machines. Good duration, and topics are well divided between the episodes. Top job. Very much appreciated.
YOU SPEAK SOFTY AND SLOWLY WHICH MAKES listening to you a pleasure and the fact that you don't rattle away like a machine gun means your content is easier to absorb and understand. So very well done and thank you for the upload! BTW didn't know about the prime number consideration but, of course, it makes perfect sense. Subscribed !
The USN experimented with pump jet propulsion on the USS Glover for surface ships in the 60s. Glover was a very heavily modified Garcia class frigate (hence Glover class) testing out a variety of sound reducing technologies. Some of which went on to be widely adopted, like the Prairie and Masker bubble systems, and some not, like the pump jet. It also was the testbed for various sonar systems throughout it's existence.
And the pump jet was actually invented by a new zealander and was actually first used on a boat by an Italian that was funded by the Italian navy , whats your point ?
@@Stevie-J The point is he said the US experimented with jet propulsion on a surface ship clearly trying to say it's a US invention when it clearly is not , that would be like me listening to a lecture on TVs and my lecturing saying the TV was invented by a Scotsman and then i blurt out but the US sells the most TVs ..... it's like yes ??? and ?? your point is what ? The TV was still invented by a Scotsman and jet propulsion was still invented by a Kiwi.
I'd be interested to know when you were on Glover. The last 2.5 yrs I spent in the Navy, I worked in the Vibration Analysis shop (92a) @ 32nd St. in San Diego. We were (supposedly) setting the ground work to reduce or modify the sound signatures of surface vessels (targets😊). That was 76-78. I had never heard of this type of project
I am fairly sure that the prop you showed fitted to the courageous was not an "operational" propeller. Back in the day we used to fit standard props to platforms whilst carrying out non-operational tasks. Prop changes, carried out alongside or in the dock were a normal procedure prior to going out on operational deployments. This was the same for all the V, C & R boats.
Very informative, good sound engineering principles you explained very well. I have never heard such a precise and comprehensive video before. (and I view a good number of technology videos) excellent work! Thank you
if this was unscripted, no matter-- we liked the delivery, smooth and relatively free of ad lib corrections. Clearly, you know the material so well, you do not need a scripted approach.
The chips on the blades are generally the result of erosion rather than strike damage. I cannot comment more on the propulsor but if you can contra-rotate the turbulence within in the wake aft of the screw without using a mechanical contra rotating device, that would reduce turbulent noise from the wake (it can be done). There a a lot of things hidden in good designs that critical for them to work. Stealth is in the silent service better than speed as we discussed. An excellent piece on a very sensitive matter. Regards
@@VistaThaiGuy Yes exactly that; the "bubbles " of cavities particularly at the tip create an explosive decompression that causes significant damage to metal of the blades (not much will resist the force such as ceramics and all sorts of materials) you have to avoid creating them. The prop shown with the chips on I guarantee will have been a noisy prop.
@@johnhargreaves3620 not sure explosive decompression is the correct description. The fluid does vaporize due to localized areas of low pressure, but the formation of pockets of vapor attached to the surface, in & of itself, is not the problem. The problem arises when these vapor pockets split & collapse, creating high velocity jets of fluid & very high pressures & temperatures as the very tiny wall of water impacts the surface, eroding said surface in the process. Or at least that's my understanding 15 years after my last fluid dynamics class, anyway. :)
@@Iceberg86300 Yes the process is very complex and I felt that an explosive decompression would be what the majority of people would understand as a simplification. My academic knowledge of fluid dynamics was learned in the 1970s and refined by experience and testing since; the edge and tip velocities are the problem in the fluid; your objective is to reduce the effect like the curved scimitar blades or other methods we pioneered in the propulsor design. Over the years from concept the propulsor design has been refined with design changes and live test runs on boats to steadily improve the noise levels, we have stayed with the propulsor because we have found by gradual improvements in the design we can reduce the noise signature quite substantially. I was principally a chemist and engineer with a fair amount of corrosion/erosion experience ( with one or two other little specialties thrown in over the past fifty years, yes I am that old now and a little strange). Kind regards
yah i would have said that is cavitation damage. as the tips and front edge seem undamaged. normally if a prop hit bottom its the front and tip that show damage not the following edge as we see in the photo.
Firstly, let me echo all of the positive platitudes expressed before this post. And let me add a BTW, I actually prefer this microphone set-up. I feel that it significantly cut down on some incidental noises (transients?) while not degrading the overall audio quality. Thank you.
Great video as always. But there is one quite important thing, you did not clarify: Now is it true that pumpjet submarines can only stay underwater for 20 minutes?
Good point. Maybe, pitting fore sure. Was thinking that the fact that they are at the leading edge of the first row of blades made me think it's more like impact, which is also a thing obviously. Many nuclear boats cannot bottom out so I guess that they get less damage
@@HISuttonCovertShores With how much crap is dumped into and floating around in the water I doubt it's a requirement to hit the bottom to take leading edge propeller damage. An encounter with some half sunk logs or spilled contents of an overboard cargo container or Phillip the Sea Manatee (R.I.P. lil guy) could do it. That or just the people removing and transporting it to a museum not caring about babying it since it was just a display piece so who cares if the forklift ran into it a couple of times...
Hello H.I. Sutton, thank you for another great video. I appreciate the dense information and related pictures, which are very helpful to visualze that given information. Please keep on making such videos. Regarding the russian doublescrew: may I suggest another reason for the damage on the trailing edges of some of the blades? I think they are caused by cavitation. The notches are forming not on the outermost points of the blades but at the point where the waterstream most likely departs from the surface of the blades. The little bubbles which are forming when the screw is cavitating do not create noise only but are also ripping constantly on the surface of the propeller. I'm not sure about the metal finishing of russain screws after casting, but I highly doubt that those parts were not polished out for leaving as few points of attack for those destructive elements as possible. So if you look at the blade under the right damaged one, the one which is lighted the best/reflects the most, you can see that the surface of the blade gets more "freckled" to the outside of the diameter. The trailing edge here seems a bit uneven but shows no notches on the edge at all.
just thought of something..... I am assuming the submarine can go in reverse obviously not as efficiently but then they would no longer be inlets ... lol
One development I would expect to see is something already used in some helicopter tail rotors. Unevenly spaced blades. When designed properly this reduces greatly the noise caused by the blade hitting the wake of a strut or of the preceding blade, but I suspect they are optimized for a specific RPM regime.
Car tire water-dispersal grooves vary quite a bit in width, you might be surprise to look at one. They used to be all the same width on a give tire (e.g, a groove every 2cm or something) but that creates a strong energy at one specific frequency which is an annoying buzz or drone. The varying groove spacing creates the same amount of energy but spreads it over a lot more frequencies, creating "white noise" more similar to a wind sound. I'm not sure if this has any useful parallel in propeller design.
Well done . I grew up in New London Ct on the Thames River directly across from General Dynamics Electric Boat division with the Navy Sub base just up the river . Seeing subs go by in a almost daily basis was what we grew up with . I ended up working “ the boat “ from 1978 thru 1978 . Anytime we had a sub in dry dock the propellers were always shrouded and those were truly some of the most “ black art “ aspects of the entire machine . Even to this day whenever I am on the water in San Diego i see the props covered at the sub base facility they have there . There is similar science applied with torpedo props as well by the way . Thanks for the excellent explanation .
I was a Navy Diver stationed on an ASR, Sub rescue/towboat, homeported in Charleston. We had to take over the work for the ASR homeported in Groton while it was drydocked. We pulled in during a winter trip and I saw the local Navy Dive boat tied up alongside a sub. When we left the next morning, the tugs that assisted us getting underway and in the river channel had broken thru a layer of ice that had formed on the river overnight. As we passed the sub with the dive boat, there was a diver with a big iron pick bar bashing a hole in the ice so they could dive. In an instant I resolved to never, never, ever, let them station me in this frozen diver's hell. I've seen, cleaned and inspected most of US screw types, except the pump types as they showed up after I got out. I ran the first ever waterborne screw change on a Trident. I probably passed you on that frozen winter morning. Hooya!
@@careyrose6059hey Carey. When were you in Charleston? I was on Orion from 73-78. Trying to remember the ASR we had then, I think it was Petral if I recall correctly.
There is a lot of other noise that they make aside from only the screw, so that would be like putting on a wig, might work for a short while at a distance but would soon be identified and cataloged as the new signature for that particular sub.
This was great. First time I've seen actual pics of that nine bladed screw the earlier RN boats had. Glad to hear the _Courageous_ museum is actually happening too. Shame it couldn't be _Conqueror_ though!
@@rosswhite-chinnery5725 i have no idea and i would suspect its probably classified what the problem is. but she was and has had for along time a contamination issue of some kind. she was supposedly known as a "sick boat" even when still in service.
Sutton when you say you dont think we will see a worm drive in the future, are you referring to the MHD drives such as the ones fitted to Yamato 1? (probably a dead end as quiet but not very efficient energy wise) or an Archimedes Screw (called a worm drive in mechanics), which some small boats use due to higher damage resistance/less chance of fouling and better acceleration. I think with the advances in electric propulsion mounting motors outside the hull these may possibly have a future due to their extreme efficiency and more compact diameter allowing fitting to the sides of submarines.
I too wondered what he meant with worm drive at 19:39. A worm drive is a certain kind of gear and has nothing to do with propulsion. My guess is he mixed it up with what is called caterpillar drive in the film The hunt for Red October (maybe also in the book) which is the fictional name there for magnetohydrodynamic drive like that of Yamato 1. Worms resemble caterpillars so that might have caused a slip of tongue.
I guess what we are talking about here is a pump inducer. These are good for achieving a significant pressure rise with good margin to cavitation. You often see them employed as a pre-stage (before a conventional centrifugal impellor) on rocket engine turbopumps where the power density is huge but cavitation must be avoided. Thing is though, for submarine propulsion what we want is a high volumetric flow-rate device with little pressure rise, not the other way round. So I don't think you'll see them employed here.
Excellent, thank you! I have painted many a model, and not fully understood the various designs, and now I do. I wonder if the designs vary also based on the primary use being blue-water vs littoral? Do you think they could design the propulsion to be in-board, kinda like a jet-ski uses?
The secrecy about pump jets has more of a historic reason. The design principles of pump jets are pretty much universally known nowadays and can be found in textbooks. They look pretty much like a single axial compressor stage of a turbojet, with slightly different blade design to adjust to the fact that water is much less compressible than air. The blade ratio of rotor to stator blades is a tiny secret left, that defines the acoustic signature of a boat, but... there is a very limited number of reasonable combinations available that all naval engineers will figure out very quickly.
It's actually an axial flow water jet like in high speed water craft. The priciples are quite well known but the secret sauce would be the impeller/stator design hence the coverings.
I very distinctly remember the International Bruhaha when 2 Japanese Companies - 1 selling the actual machining equipment, and the other selling the computer control systems, (remember, this was very early in the CAD/CAM era) between themselves sold the USSR all the equipment necessary to manufacture submarine propellers to US/NATO standards.
For the "future" (the outside driven Pumpjets) I'd say there might be one additional huge benefit that it might allow direct electrical drive without gears because the motor diameter is huge, ideal for the required torque.
But woulodn't you still need some sort of gearing to turn Battery electric power into mechanical power to power a submarine? Example Washing amching motor to drive a train car
@@rayRay-pw6gz yes but but Teslas are powered by batteries, and anything that can generate enough electrical power to run a pump jet like that is going to have a nuclear reactor
@@Laotzu.Goldbug I agree with you on the power plant on a submarine. But, the line of thought was the removal of the gear box . The motor and pump jet are on the outer hull. No main shaft thru hull.
thank you for this video Mr Sutton! I learned a great deal! and i will be applying this to my RC submarine builds. I have a 50" Virginia in the works right now that will benefit from this video.
Sounds like a cool project. I know that in scale model airplanes they can't generally fly them with scale propellers because air molecules don't get smaller when you shrink the plane down, but I suppose a scale prop on a sub would just underperform, not fail to work completely.
@@AlRoderick scale props do work on subs decently. However I 3d printed a custom one that’s more like an impeller so we will see how that works once it gets a bit warmer where I live. Too damn cold to primer and paint right now
A lot of Soviet boats had small electric thrusters on their stern planes, but I believe these were more for maneuvering than stealth. In fact I am pretty sure I've heard that the "spinners" were actually noisier than the main propulsion (probably because they operated very high revolutions). I do recall reading in one source a long time ago that the early Soviet nuclear boats like the _Novembers_ and _Hotels_ had electric "creep" motors but these seem to have been an alternative means of driving the main propulsion at low revs rather than being shafted to their own separate set of screws.
First-time watcher. Nice format. I do audio software and am puzzled how it could be that prime-bladed blades have anything special about their harmonics. Any propeller etc. should have a base frequency of the time for 360 degree rotation, with a very strong harmonic at the number of blades. Then that harmonic would itself have many strong harmonic, due to the "swoosh" of the blade going by not being a sine wave. The base frequency would be nearly zero audio strength unless the blades differed (accidents, damage from cavitation, uneven spacing, etc.) But I don't see how say a six- and seven-bladed propeller would have a drastically in any of this. I sensed some hand-waving when the subject came up and would like a more specific explanation.
What he referred to as harmonics is not the harmonic frequency of the screw itself, but how it can cross or harmonize or reinforce when other basic frequencies like 2 or 4 per 360 also exists… if you want to know where 2 or 4 per 360 came from, look at the number of rudders…
@@Skyshade Blade designer for sub must try the "frequency. cancelling system" in reducing noise...Its has been an 80's decade technology: A noise detector will identify the noise frequency number, then the computer will generate a duplicate negative frequency - to cancel the existing noise. Another idea: The substance used by fast swimming fish should be identified - then alloyed to the molten metal of the sub propeller during moulding....Also try to put some boron as alloying additives....The Bible said in book of Ecclesiastes 1:9-10 "There is no new new things under the sun..."...you cant invent a new things,everything has been existing already- all scientist, inventors,designers,etc to do is to imitate God engineering, principles, system,etc found on His created animals,fishes, birds,plants,micro.organism,others creation.... Such Biblical fact is one of many secret of Israel why they are very efficient and prolific when it come to inventions,designings,etc
I found this on Quora (based on this comment I believe "odd" is the the right word to use more than "prime"): The first nuclear powered Albacore hulled submarines had five bladed screws of conventional profile. As the conventional profile propeller blades passed from disturbed and back to undisturbed flow, the propeller blades would flex longitudinally, emitting “blade rate” acoustic energy. To reduce the emitted blade rate acoustic energy, two changes were made to the screw: 1) blade profile was changed from a conventional shamrock leaf shape to a skewed, banana shape - this reduced the blade flexing by having only a portion of the skewed banana blade cutting through each disturbed flow region at a time, stretching out the transitions through the different flow regions to reduce blade flexing. 2) number of blades was changed from five to seven, to reduce individual blade loading and thereby individual blade flexing. An odd number of blades is used so that only one blade at a time will be going through the disturbed flow area behind each of the four control surfaces. A very secondary effect is that for a given shaft RPM, the blade rate of a seven bladed screw compared to a five bladed screw results in greater acoustic energy attenuation (the slope of the attenuation/frequency curve is roughly 7 dB/decade per thousand yards)
@@lqr824 - Like you, I was puzzled by why a prime number of propeller blades should be so significant, and following the same rationale as you provided. The explanation for selection of number of blades probably lies in the response provided by Skyshade and a few other posts in response to this video. So if you stuck a 4 blade propeller behind a typical set of 4 planes at 90 degrees separation, that would be a bad idea due to interaction of the blades with the wake field. An 8 blade propeller would probably also not be ideal for this case. Not that I know of any submarines that only have 3 equally spaced planes aft, but if you stuck a 3 blade propeller (a prime number) behind them, that would also be a bad idea, as would a 6 blade propeller.
There is a good reason for SSK's not to have a pump jet and its the same reason that merchant vessels don't have Kort Nozzles ( a pump jet is simply a very very well engineered type of Kort Nozzle ). The reason is drag , the nozzle/shroud is heavy and produces a fair amount of drag so merchant ships ( even the largest ULCC oil tankers ) have an open propeller as it uses considerably less fuel for a given speed and allows the ship to have a faster cruising speed. On fishing boats only those that tow gear ( trawlers/beam trawlers/scallop dredgers ) have Kort Nozzles as those work at far higher efficiency at medium RPM but low hull speed ( you get about 35% more bollard pull from a well designed Kort Nozzle than an open propeller so when towing gear it saves a lot of fuel which over a year means large fuel savings even considering transit time steaming to and from the grounds ). Those fishing boats built to fish static gear ( pots / gill nets / longlines ) only use an open propeller as that saves them a lot in fuel over a year due to not having the extra weight and drag of a kort nozzle set up
What do you do for a living if you don't mind me asking? I have been building and repairing ship and tugboat propellers for 25 years and I have nothing to add to your comment is why I ask. I've built and repaired propellers from Aircraft Carrier size on down to impellers on Seadoo's.
@@mikebrase5161 I'm a retired ( knackered back sadly ) Fishery Scientist, I was a commercial trawlerman before that. Always been interested in how to use less fuel for a given speed/bollard pull and advances in the design of modern fishing boats means you can build a boat of more than twice the displacement on the same length with a larger engine and use less fuel overall , the new kort nozzles are now around 40% more efficient than an open prop when towing gear at 4knots. A Kort system does cost a lot more than an open prop but trawlers will see fuel savings meaning the nozzle pays for itself within 3 years
@@DavieTait I did something you might find interesting. I took all of the specs for the Queen Elizabeth class Battleship I got lucky when I came across the reduction gear ratio used. I wanted to see how much we could raise its not speed with modern Prop styles. With a modern 5 Blade High skew which was a fairytale back then, the speed increase was 4 knots without a loss in Fuel efficiancy which if I remember was around 80%. I've worked inside more Nozzles than I can count. They were definitely a game changer especially for the Push/ Pull Tug boats which is mainly what I work on currently. The company I work for has built the majority of Tug props on the Mississippi river. My favorite is at least once a year we have to send a tech out to recut the Diameter because a customer will measure the outside of the nozzle not taking into consideration the taper to the inside dia. We even have it in Red on the spec sheet for customers to fill out when they make the order. I had to fly to Tonga before Covid it was awesome hahaha. Best customer paid vacation ever.
Good additional info about Kort nozzles. I had the intuition about this, but you gave the right words to explain it better noting drag. Maybe not mentioned but a very basic statement would be Kort nozzles are best for high thrust needs. So Towboats. Modern port towboats have azimuth thrusters for maximums maneuverability and maximum pull. As you said.. they move slow but move lots of water which the Kort nozzle is good for. Another thought, there is always a single ideal speed and rpm for a propeller, so the choice of propulsion has to take into account a usage profile, maximizing operating conditions and their frequency and importance.
Davie Tait: I would have commented much the same as you on the matter of pump jets / ducted propellers and their use on SSK's, but as far as I am aware from what was in the public domain, the now cancelled Attack Class SSK's intended for the Royal Australian Navy would have had pumpjets fitted. I am left to wonder whether the prospect of a lower signature would have come at the cost of reduced underwater range / endurance compared to an optimised open propeller?
Refreshing change from the normal video that, as an example some guy showing a lake and all you see is a face. This is a learning experience and thank you for that. I was in the USAF and know nothing of submarines. Now I do, thanks.
Thank you, your videos are so interesting. My Dad would have loved watching them, unfortunately he died before the internet age. He was the senior test Engineer for the UK nuke sub program in the early 60's, after getting trained in USA in Pennsylvania. Your videos would have been totally followed by him, and no doubt added to with commentary.
Nice work, I really enjoy all of your videos. A thought on the dubble screw and your comment on the damages on the blades. I believe that the damages on the edges of the dubble screw is wear from cavitation. I'm certainly no expert in hydrodynamics but I do know that cavitation is the result of too low pressure at the trailing edge of the blade which certainly seems to fit with where the damages are located. With a dubble screw setup, the first screw blade will be more susceptible to cavitation issues than with a traditional one screw setup as the next set of blade will decrease pressure between the screws, thus making it even harder to avoid cavitation. Of course the offset of the two screws will mitigate this issue but I can't but think that at some speeds (accelerations) the trail of the first screw will line up with the second. This is where the counter rotating screws come in 😉
to be fair, i found this by accident.however i decided to watch it and i actually learned something worth knowing today. great informative video. thankyou. now subscribed
Red October in the movie used Magneto Hydrodynamic Drives (Caterpillar Drives they called them). This is a drive technology with no moving parts as it relies on moving the water with magnetism. It's actually a real technology but not very efficient if I recall correctly.
@@shaider1982 true the weakness of super conductors has been their need for cryo cooling. Recent advances have brought them temperature up significantly.
A video or article about the concept submarines of Naval Group (formally DCNS) would be really interesting. Between SMX-21 and SMX-31E (shown at the end of th video) they had a lot of creative and differnt ideas.
Something I've not seen here is any mention of unevenly-spaced blades. I remember asking my Dad why the cooling fan on our Ford Cortina had the blades unevenly distributed around the centre. Dad (who is an engineer and used to be editor of OEM design) said that it was to mix up the frequencies of sound produced and to avoid producing a more noticeable constant hum of a specific frequency for a given engine speed. Given the the key to propulsion in a submarine is stealth, has this concept not been tried on submarines?
I think this was touched on when he mentioned skew-back screws having prime numbers of blades to avoid getting a harmonic resonance. You might be able to reduce this even more by having unevenly spaced ones but you would likely significantly reduce the efficiency of the submarine without a commensurate decrease in audible signature making it worthwhile. Since the radiator in your car doesn't have to worry too much about efficiency, and the subjective noise quality is all that matters, it's a good trade-off in that case. Also, I'm not entirely sure so an engineer can correct me if I'm wrong, but I think that in unevenly spaced propeller would create uneven propulsion, requiring a constant steering correction just to go straight. Obviously this is not desirable on a submarine.
Ducts are there to prevent wing tip vortex which creates cavitation.They also camouflage noise source.On submarines any type of vortices are not acceptable they create noise and drop performance.Screw backs are built to prevent wing tip vortices as well. Center of propellers turn slowly while tips of propellers turn at high speed.So foil thickness to chord ratio must be different for efficiency.Higher the speed longer the cord to thickness ratio and higher rake for preventing cavitation performance.Note there are more rake at tips.I am a speed sailor on windsurf so I have spend much time searching fin designs for speeding.New propeller blades are basically twisted fins or foils with asymmetric foil shapes.I shape my fins asymmetrical they do perform better on one way starboard or port ride.I like pump jets they will get better by time ducts will help protecting blades against shocks as well.Counter rotation duo props are good on performance by straight flow instead of vortex flow but counter rotating blades may create more cavitation because of sudden flow change.
This might sound weird but this video reminds me: Have you thought about doing a video on the submarine from SeaQuest DSV? If I recall it had some really unusual but plausible technology at work.
Any chance for a video about the structural considerations of the submarine? E.g. pressure, width to beam ratio, internal frame, do they study things like resonance frequencies of the rooms inside the ship while it's being designed, or there's so much stuff that it's not an issue?
A resonance problem nearly pulled the Nautilius apart on its return from a round the world cruise about 70 years ago. Eliminating a bump on the lip of ballast tank opening beneath the hull turned the tank a police whistle at high speed. Also, cavitation occurs during high activity -- like a hickey;
Hi, Great video. Really interesting. No rubbish music. All pictures identified rather than most which use random anonymous pics. how does the sycle blade cut the noise? I understand large slow turning but......
Thank you for giving me a research term!! I've seen "Annular Screws" on submarine models, or pictures of models, but I never knew what to call it to learn more about it or why it ever existed in the first place. Most of my knowledge comes from airplanes, so my only guess is that the ring is meant to prevent tip-vortices from generating, but as it seems to be rare, and to even have gone out of fashion, I'm guessing it didn't work?
Some LA688Is use/used an annular screw. Not sure if current, but certainly in the late 80s/early 90s was introduced. Proposition was that the connecting ring eliminated tip vorticies and reduced blade flex. Sometimes also called the "ice ring" screw (at least in USN service), and might have had an additional functional use for boats working in icy waters as a means to presumably protect against tip-strike. LA688I annular screw image: www.mulsannescorner.com/models/Submarines/LosAngelesclassSSN/01.jpg
I remember relieving the throttleman for a head call during a northern run and answering bells concurrent with a call from up forward with the instruction to answer all bells until cavitation is noted after which additional turns shall.not be made. Exciting run that one.
No, when a submarine enters dry dock, and sometimes if a boat is in a hard running period (sea time, and even more sea time) the boat below the water line will be cleared of weed and such, particular attention is given to the screw or propulsor. The boat will use its own divers to carry out this task OR if CDs (Clearence Divers, underwater bomb disposal experts, these guys are totally insane - and exceptionally highly trained and their courage is not in doubt) are available then they'll come along and 'dive on the boat' while alongside. If the boat goes into dry dock (about once every year, ish) then the whole boat is scoured of marine growth, old paint is 'harben gunned (think a patio washer on steroids) away from the pressure hull, then 'chocolate coloured "admar" (ADmiralty MARine) paint is applied, when dry the whole shebang is painted a cheerful 'losheen black colour' (it goes on shiny and drys to a cheerful dullllllll black). Measurements are done on the propulsor to check that the rotors inside the duct are within tolerance to avoiding touching the shroud. The shroud was known to move now and again (the whole unit was VERY heavy). Once all work was compleat, inside and outside, the dock was flooded up, the boat moved back to a tidal berth and after a VERY, VERY intense work up, usually taking two months from start to finish, the boat is passed fit to go back to frontline duties. For us that meant back where we truly belonged - inside their back yard and mixing it with the big boys!
@@petewilliams.1122 Thank you Pete for your comprehensive reply. 👍 I'm on holiday right now on the Isle of Cumbrae (Great Cumbrae at the end of the Firth of Clyde) and a few of days ago there was a lot of coming and going from Faslane Naval Base. I saw a Dreadnought class boat, a Los Angeles class boat, but I'm not 100% on either, a destroyer and at least two helicopters. The American submarine was visiting Faslane according to a friend who works there, but with all the commotion I wonder if it was a bit more than that. There's talk of Russians and Western undersea assets. We'll be able to read what's actually going on in a few decades. We're definitely in the Second Cold War, but just like the First, people won't accept it for a while. I hope that you enjoyed your time in the service and I do appreciate it. "in their back yard" sounds great. 👍 Look after yourself.
I find it interesting that flip the skew around and we get basically the history of computer fans. Look at a Phanteks T30, Noctua a12x25, Arctic P12, or some Zalman or Asus annular gpu fans. The reason is exactly the same: lowering the noise.
NO 12:48 I WAS INTERESTED man I love your videos. now I will not die happy unless I figure out what info you were about to provide. I used to hate subs. now I love em, watch these all day at work. thanks boss
I don't believe anything in the water would be immune. Water carries sound way farther than air. Granted if isothermic. But even if there was a temperature chamge and the sub hid below it. We would still drop a temp bouy to get that reading to find it
@@stevenc8140 I think it's like air to air radar guided missiles don't have the ability to attack ground targets , because they don't have a way to separate the target from the earth . So torpedo don't don't work and old fashion depth charges will move the entire mini submarine instead of collapsing the hull. So you can find it on side scan sonar but you can't attack it and it can still attack you.
That would be Senator Pauline Hanson who has been making her own, shall we say "interesting" contribution to the political discourse of this great country since 1998. (Stints in jail and on _Dancing with the Stars_ notwithstanding.)
I worked in Kiel a couple of years ago. Could see the Subs come in from my office. Sometimes one of them was playing the pirates of the caribien theme on speaker when sailing in with crew on deck, (if i remember correctly).
so back in the early industrialized wars, mainly WW1 , surface ships used various paint schemes to thwart visual targeting and identification i wonder if there is an analogy here for the sound signatures of submarines, for example varying the pitch of the static blades, or having an independently rotating vortex diffuser or perhaps even changing the mechanical properties of internal components to alter the acoustic signature of the propulsion, such as bearings which can be repositioned along the length of long shafts, or mounting machinery on dampeners with adjustable tension and stiffness, which could all be actuated electronically and simultaneously so as to obfuscate the submarine's identity, or perhaps even configured in a specific way to mimic another craft
One technology used to reduce sound outside submarines is frequency smoothing. If you have something that makes sound, you deliberately mismatch the parts that make the sound so that they don't sync up. For instance, a tyre tread is made in very uneven arrays, so that the sound generated isn't in one frequency, but across many frequencies. That means that in any frequency you are hearing in, the decibels is much lower. I'm not sure if the secondary blades are all matching perfectly in a prime series or of they also arrange them to be mismatching and breaking up frequencies.
Wow, waaay too long between videos. I’d like to see a video on nuclear submarine detection. Most notably that nuclear reactors specifically release nano particles called anitneutrenos. Many tests have been done to detect anti neutrenos. To what capacity is it feasible to employ these devices to detect nuclear submarines?
Our college Radiation Physics professor said neutrino was very penetrating,any thickness of lead,heavy metal,etc is nothing to its penetrarion power,it can easily pass.thru....So maybe it produced a mutant,abnormally behaving molecules of flying submarine wall materials,also of sea water outside of submarine- thus,if a detector can be invented, all nuclear powered submarine will be tracked in the long run
@@fortunatodeguzman8017 absolutely. Electron-antineutrinos are abundantly produced by the nuclear fission reactions inside the reactor cores (6 νe are produced in the uranium fission induced by neutrons [Way48]). A typical ~ 1 GW standard nuclear plant radiates about 5.1020 antineutrinos per second; their energy spectrum extends to 10 MeV and their mean energy is around 4 MeV. So quite a lot of detectable energy being emitted. The game has changed
@@MrSubmariner76 Neutrinos are notoriously hard to detect.... they carry no electric charge so they have to hit matter that can give off a charge...and the chance of hitting another particle are slim. Is the energy you are mentioning the amount typically released upon hitting another particle or the amount of energy related to its mass? Also, a sub's reactor would be what, 1/20 or 1/25 at speed of your 1 GW reactor?
Maybe electric driven rim pumpjets, could be fitted with deflecting horizontal and vertical fins at the end of the tube ducting channel, plus fitting upto three or four rim pumpjets being installed. With four rim pumpjet of them fitted around the hull, spaced at 90 degrees apart either above and below plus on either side of the hull? Or four rimjets positioned two on either side of the hull, but on near the top of the hull and the other near the bottom of the hull on each side of the hull. Or just three rim pumpjets spaced out 120 degrees apart, but with these rim pumpjet propellor blade, actually having a double or triple propellor blade layout, with 5 blades, then a set of 7 blades plus 11 blades? Also using replacable interchangeable compsite-alloy blades, with these blades maybe coated with a ceramic layers, to protect the blades from damage and from corrosion too. Or maybe in the future submarines and surface ships, will both be fitted with multiple rim pumpjets in a series within an extended ducted housing, along the side of the hull for upto half or three quarters of the hull length, to create a very silent and quite propulsion system at high speeds? In way creating a worm drive like system, as suggested in the novel Hunt for Red October.
Very interesting stuff from the more (well, more than the average) technical side of things. Very good explanations of stuff that's somewhat secretive. I'd love to hear something about the Toshiba-Kongsberg scandal - which saw Western-aligned countries funneling CAD/CAM equipment to Russia to help them make quieter propellors.
I'm curious what is the fastest non-nuclear powered submarine currently in service? And will we see Pump-jet be viable in higher speed conventionally-powered submarines?
What about having a pumpjet inside the hull itself? So you have an intake or multiple towards the from of the sub, that water travels through a system of pipes to the pumpjet and is then expended from a long tube towards the back. Obviously that'd take a ton of space but it would reduce the noise quite a bit, in theory. I'm sure it's totally impractical but I think it's a neat idea.
Reason iits not done is because like ordinary props the bit that creats to biggest noise is in fact tbe water boiling on the very edge of the blade due to compression, the same thing happens with a pump net so this is why its not done. There is a way round this but is so fundimentally different that it has yet to be tried, that is to have the intake at the front of the sub so that the sub itself absorbs much of the noise, also from a damabe control outlook it would be a real headache.
It's not a clear photo and it's difficult to make out the sickle shape. I wondered if it was an attempt to stop tip-vortices by bending the tips over, like with aircraft "winglets". I'm sure blade "winglets" would have been tried but, apparently, not successfully.
Interesting. I am a retired US Navy submariner. I remember the screws well. I recall being told that the number of sickle blades on the screw was classified. There were seven. I always thought that ridiculous since the floating dry dock in Scotland was open at both ends. Even with the screw covered by a shroud, all anyone needed to do was count the peaks on the shroud.
@@parallax9084 I highly doubt it. If you notice in some of the more modern submarine movies, the screws are frequently depicted with seven sickle shaped blades. There's also photos of submarines all over the place im drydocks where the screw is plainly visible.
Allow me to correct a couple of errors. The first of class HMS Swiftsure, and first of class HMS Trafalgar both had nine bladed screws. The rest of the S boats had pump jet propulsors. The rest of the T boats had pre swirl pump jets or PSPJ, ( I am not allowed to quote the number of blades or rotor design because of the OSA). Further... NINE blades does not equal frailty or anything like your suggested weakness. Both Swiftsure and Trafalgar had great success with their very robust 1X9 fit with superb low revs equaling very low turns per knot or TPK. With hardly any revs on at all these boats would fly. Both 1X9 screws were gigantic, 20 feet in diameter and at the time they both had the lowest TPK in the world (I know of what I speak).Becsause of the size of the screws both Swiftsure and Trafalgar were fitted with BIG rudders, the follow on S boats had small rudders. ALL the T boats had big rudders. Both screws were made of nickalium and were true feats of engineering. With exceptionally low revs came the advantage of being able to have an excellent reduction ratio of engine to shaft (once again I am not able to quote numbers because of the OSA). On one occasion during my time on Swiftsure we needed battle short revs astern, we dragged THREE ocean going tugs 100 yards astern with us, the ocean going tugs bully supertankers in their day to day lives, they felt the raw power of an S class SSN that day. One another occasion we needed full ahead revs to get out of a situation faster than we got into it (always have that ability). In no time flat we exceeded thirty knots and we were NOT cavitatting!!!! Like I said, these screws were GIGANTIC± HMS Churchill was the first SSN in the RN to have a pump jet, Once the design was proven she reverted back to a screw. Once the USA saw that prolusors were not going to fail drastically and that the Brits had made them work then they wanted in. PSPJs fitted to the T boats were and are still exceptionally quiet. I expect the same to be said of the A boats and the bombers. I hope this has been informative. 👍
Thanks, yes good info. Was aware re first of class having the screw, just not going into so much detail in a video. Re fragility, interesting. But have got the frailty from somewhere. You might like my article and cutaway of the T-boat. Not intended to be 100% accurate for very obvious reasons, but hopefully captures the feel. Also, mix of individual boats in internal arrangements. www.hisutton.com/Royal-Navy-Trafalgar-Class-Submarine.html
@@HISuttonCovertShores The T boat accommodation ladder (from the main access hatch to the control room), the first nine feet or so is straight up and down fore and aft, and then (the next six feet or so) slants to starboard, well it was when I shipped out on the black pigs! I remember showing some former German U boat captains around. When told that at the bottom of the accommodation ladder they were already fifteen feet underwater, their eyes became wider and wider, I heard a genuine comment, 'what could we have done with one of these...' I'm sure they were all contrite National Socialists! When they saw the bomb shop however...
Since this isn't classified or need to know information, i'll tell you the main reason they hide propellers on submarines. If you can measure the general size, shape, and the number of fins on the screw; you can calculate the sonar signature of the screw. You then add this to your shipboard sonar library to use in helping you identify submarines and ships. It's as simple as that. You wouldn't believe how much time is spent on recording and cataloging sonar signatures.
Being a veteran submariner. I have to say you are correct.
I worked in ASW in the Navy for over 20 years and you are absolutely correct sir
@@dspates51 Sir,why those sub designer refuse to imitate the way squid travel in water?..I think the jet engine idea was derived from the squid swimming system,thus the phase.out of propeller type plane engine in favor of the jet engine. What happen to the plan to duplicate the design of fish tails,fins, etc in their swimming method?..I think naval engineers had already figure.out how fast swimmer fish do their craft via their amazing tail...Is the fish propulsion system hard to duplicate?..
Yup. Wonder if those new 11 blade props will be adaptable to submarine use.
I thought it was more for design and concepts because a lot of technology and design goes into the blades to help stop cavitations that destroy propellers I didn't realize you could figure out the sonar signature that's truly impressive
Prime numbers to avoid harmonics. This is an astonishing revelation to me at my old age. I never thought of that, not once. Fascinating video.
how does it work?
@@Loquacious_Jackson Harmonics are integer multiples of the the base frequency. 2, 3, 4, 5, 6 would be the harmonics below 7, and 7 is not divisible by any of them. Would work with 5 too, or 11 - but that's a lot of blades.
@@u_u4640 yeah, I still don't get it 😂
Primes are amazing, often come up with very simple applications. In this case I'd assume harmonic waves would cause strengthening of those waves (=constructive interferecens), like pushing a child on a swing at regular intervals would increase kid's speed, whereas pulses with irregular intervals (which you get with primes) would cause non-harmonic waves, causing destructive interference instead
Well done, H. I. Sutton. Very well done, Bravo, sir. Thank you for doing a video that I could never create with getting arrested.
HELLO SUB BRIEF!
FBI, OPEN UP
Darrell is getting twitchy!
Nobody can knock you for staying on the safe side of the line. It’s understandable that your knowledge also contains official reasoning, instead of just intelligent analysis that can point out multiple characteristics without knowing how important each was in the official decision process
Turkey, we need you OUT of prison to make more sub briefs and grace us with hilarious cold waters gameplay!.
"Were not supposed to see insde them...so lets see inside them" cracked me up
I have never been so enthralled by an off the cuff, almost fireside style chat about a topic I thought I had absolutely no interest in. Nice Work
Wow, thank you
Fantastic stuff. No annoying dubstep music no needless glitz - right to point and technical. Love it, thank you very much!
This is next level! Thank you!
I was so sick and tired of the typical "content creators", who, much like cheap copies of a Discovery Channel lay the focus on "exciting" and neglected "interesting" and "well researched".
With your content, it is exactly the opposite. Highly knowledgeable individual giving an unscripted, in-depth talk with "simple" imagery.
Well worth the wait between videos. For me, right up there with Greg's channel on aircraft and engines.
Wow, thanks! I think I know the channel you mean. Not sure I am in that league, but I will take the compliment!
Agreed. One thing I can't stand, is the overly dramatic narration and focus on superlative specs and number of swimming pools, football fields, or elephants. You never really learn much about the core technology and it's just meant to impress.
@@wyskass861 🐋 don't forget the blue whales! 🐳🐳
@@wyskass861 Science is / SHOULD BE boring to listen to, because the exciting bits are the actual facts and not the "dress" in which it is presented. This focus on flashy (and often enough EMOTIONAL) narration also "hypnotises" people into STOPPING TO THINK and there is nothing better than GLOBAL WARMING to showcase it, because the ONLY SOLUTION - thanks to the "green fanatics" - is "reducing CO2", but there are at least TWO OTHERS (and a powerful reason why "managing CO2" WONT WORK):
1. "the tragedy of the commons" explains why reducing CO2 will NEVER work ... and even the most willing of countries - my country of Germany - have broken their promised reduction goals, because they simply cant bring themselves to NOT introduce the 5G phone standard which will require more power than the previous one
2. a few years back there was this volcanic eruption on Iceland, which poured loads of ash into the atmosphere, blocking air traffic over the northern Atlantic Ocean for months, but a year later some scientists speculated that it might have lowered the average temperature by 1°
3. a "solar shield in space" would reduce heat incoming from the sun, so it would even help if THE SUN is causing the increase (which we simply dont know, which is another reason why "reducing CO2" possibly wont do anything). With Elon Musk's improvements in "rocket science" (or rather: application), it should be possible to a) transport a large amount of satellites into space, which provide shade for the earth AND to haul a big asteroid from the asteroid belt into a stationary position between sun and earth.
Nobody is "thinking outside the box" like this, because the media like their sensationalised one-track-thinking ... oh and "electric cars" is another one of those topics.
Relavent imagery is really appreciated
I have a true story to tell you. Many years ago, a professor of Mechanical Engineering at the University of Hawaii, Dr. Karl Ihrig, had engineering students in his classes that were in the US Navy. He was invited to look at some nuclear submarines at Pearl Harbor as his student’s guest. In those days, the submarine screw was exposed. He looked at it and exclaimed “Wow, you can actually do XXX knots top speed?” His students were startled & asked how he did that because his figure was accurate, though classified. He said from the size & shape of the propellor, he did the calculation by eye & in his head. This stunned his students & they reported this up the chain of command. After that, the Navy started covering the propellers so that it could not be photographed, especially by satellite. Dr. Ihrig also help design the underwater BART tunnel in San Francisco in such a way that pressure would remain relatively constant (despite the rapid change in depth) by the movement of the train, making pressurized passenger cabins unneeded. It was his idea. There still is an engineering company that bears his name in San Francisco, though he sold it years ago. He has since passed away.
Oh my god. Thank you so much for not using that intro music. You can't imagine how big a relief that is on my ears.
I love how he says his work is unscripted but his presentations are always so professional.
It’s the ultimate flex!
What an excellent and thought provoking video, and as a side note, civil and thought-provoking comment section.
12:54 The erosion seen on the edges of the props is due to erosion from cavitating flow. Impellers used in hydro turbines (as used to generate power in dams) suffer from the same issue.
You know it's erosion becasue of the way the erosion looks.
You can see cavitation damage from Google Earth? You must be looking at a different picture, my friend.
Current STS here. Not much I can comment on without having to check classifications, but decent video. Some things to think about from an engineering perspective: Slower screws (lower TPK) require bigger shafts due to the high torque. This is why diesel boats don't really employ any crazy super low TPK screw designs, they don't go very fast in the first place and the extra shaft diameter would just rob them of valuable space. Also, mission matters. Pump jets only work well in one direction. Boats that need to loiter/make very controlled movements dont use them often because reverse thrust is extremely inefficient through a pumpjet.
Thanks.
Side note. USS Jimmy Carter has a pumpjet
@@HISuttonCovertShores Seawolf class submarines have propulsors. People often use the term interchangeably with pumpjet but it isn't quite the same. Either way, they are very fast but not great at slowing down.
@@Maverickib On a T boat on patrol in the MIZ (Marginal Ice Zone) we managed to operate for weeks at an average of one knot while maintaining our heading. We had what was in reality a stopped trim.
It was supposed that an SSN was deemed too big to achieve a stopped trim., NOT SO, a stopped trim can be achieved, you just have to develop the techniques and put that into practice. UK SSN crews have that ability, the are VERY highly trained.
@@petewilliams.1122 Well yeah, SSBNs hover all the time. Never said boats can't do it. Propulsors just make it more difficult. Hovering (stopped trim) is more a function of expertly controlling ballast than anything. Seawolf has a propulsor and we can still do it (I've been in the MIZ as well), we just have to be very careful when it comes to increasing speed because the propulsor makes it difficult to slow down.
Another video! Great!
I love the 'chat' format to be honest-- it's very well delivered. I like the descriptions of the remarkable and interesting features of these awesome machines. Good duration, and topics are well divided between the episodes. Top job. Very much appreciated.
YOU SPEAK SOFTY AND SLOWLY WHICH MAKES listening to you a pleasure and the fact that you don't rattle away like a machine gun means your content is easier to absorb and understand. So very well done and thank you for the upload! BTW didn't know about the prime number consideration but, of course, it makes perfect sense. Subscribed !
The USN experimented with pump jet propulsion on the USS Glover for surface ships in the 60s. Glover was a very heavily modified Garcia class frigate (hence Glover class) testing out a variety of sound reducing technologies. Some of which went on to be widely adopted, like the Prairie and Masker bubble systems, and some not, like the pump jet. It also was the testbed for various sonar systems throughout it's existence.
Like a rubber-composite exterior to the hull? That unfortunately weathers quite fast and falls off! German U Boats started that one I believe
@@stevenc8140 If it was there, it was long gone by the time I was aboard.
And the pump jet was actually invented by a new zealander and was actually first used on a boat by an Italian that was funded by the Italian navy , whats your point ?
@@Stevie-J The point is he said the US experimented with jet propulsion on a surface ship clearly trying to say it's a US invention when it clearly is not , that would be like me listening to a lecture on TVs and my lecturing saying the TV was invented by a Scotsman and then i blurt out but the US sells the most TVs ..... it's like yes ??? and ?? your point is what ? The TV was still invented by a Scotsman and jet propulsion was still invented by a Kiwi.
I'd be interested to know when you were on Glover.
The last 2.5 yrs I spent in the Navy, I worked in the Vibration Analysis shop (92a) @ 32nd St. in San Diego. We were (supposedly) setting the ground work to reduce or modify the sound signatures of surface vessels (targets😊). That was 76-78.
I had never heard of this type of project
I am fairly sure that the prop you showed fitted to the courageous was not an "operational" propeller. Back in the day we used to fit standard props to platforms whilst carrying out non-operational tasks. Prop changes, carried out alongside or in the dock were a normal procedure prior to going out on operational deployments. This was the same for all the V, C & R boats.
If possible, would you talk a little more about this? I’m really unclear as to whether or not pump jets on submarines use screws or not...
Very informative, good sound engineering principles you explained very well. I have never heard such a precise and comprehensive video before. (and I view a good number of technology videos)
excellent work! Thank you
if this was unscripted, no matter-- we liked the delivery, smooth and relatively free of ad lib corrections. Clearly, you know the material so well, you do not need a scripted approach.
The chips on the blades are generally the result of erosion rather than strike damage. I cannot comment more on the propulsor but if you can contra-rotate the turbulence within in the wake aft of the screw without using a mechanical contra rotating device, that would reduce turbulent noise from the wake (it can be done). There a a lot of things hidden in good designs that critical for them to work. Stealth is in the silent service better than speed as we discussed. An excellent piece on a very sensitive matter. Regards
Like detonation in old cars, cavitation at leading edges cause wear and pitting that result in material wear and fracture?🤔🤨😎
@@VistaThaiGuy Yes exactly that; the "bubbles " of cavities particularly at the tip create an explosive decompression that causes significant damage to metal of the blades (not much will resist the force such as ceramics and all sorts of materials) you have to avoid creating them. The prop shown with the chips on I guarantee will have been a noisy prop.
@@johnhargreaves3620 not sure explosive decompression is the correct description.
The fluid does vaporize due to localized areas of low pressure, but the formation of pockets of vapor attached to the surface, in & of itself, is not the problem. The problem arises when these vapor pockets split & collapse, creating high velocity jets of fluid & very high pressures & temperatures as the very tiny wall of water impacts the surface, eroding said surface in the process.
Or at least that's my understanding 15 years after my last fluid dynamics class, anyway. :)
@@Iceberg86300 Yes the process is very complex and I felt that an explosive decompression would be what the majority of people would understand as a simplification. My academic knowledge of fluid dynamics was learned in the 1970s and refined by experience and testing since; the edge and tip velocities are the problem in the fluid; your objective is to reduce the effect like the curved scimitar blades or other methods we pioneered in the propulsor design. Over the years from concept the propulsor design has been refined with design changes and live test runs on boats to steadily improve the noise levels, we have stayed with the propulsor because we have found by gradual improvements in the design we can reduce the noise signature quite substantially. I was principally a chemist and engineer with a fair amount of corrosion/erosion experience ( with one or two other little specialties thrown in over the past fifty years, yes I am that old now and a little strange). Kind regards
yah i would have said that is cavitation damage. as the tips and front edge seem undamaged. normally if a prop hit bottom its the front and tip that show damage not the following edge as we see in the photo.
Firstly, let me echo all of the positive platitudes expressed before this post. And let me add a BTW, I actually prefer this microphone set-up. I feel that it significantly cut down on some incidental noises (transients?) while not degrading the overall audio quality. Thank you.
Great and informative work.you have become the Scott manly of submarines.
Great video as always. But there is one quite important thing, you did not clarify:
Now is it true that pumpjet submarines can only stay underwater for 20 minutes?
haha. understood
@@HISuttonCovertShores I had no doubt you would ;)
lol, best comment
The most patient Admiral ever.
some people in our governments' man... whoa nelly...
Great brief mate, good to see some of the history behind the design. Keep em' coming!
Those notches and pits in the prop blades at 13:10 are most likely the result of cavitation.
Good point. Maybe, pitting fore sure. Was thinking that the fact that they are at the leading edge of the first row of blades made me think it's more like impact, which is also a thing obviously. Many nuclear boats cannot bottom out so I guess that they get less damage
@@HISuttonCovertShores With how much crap is dumped into and floating around in the water I doubt it's a requirement to hit the bottom to take leading edge propeller damage. An encounter with some half sunk logs or spilled contents of an overboard cargo container or Phillip the Sea Manatee (R.I.P. lil guy) could do it. That or just the people removing and transporting it to a museum not caring about babying it since it was just a display piece so who cares if the forklift ran into it a couple of times...
Hello H.I. Sutton, thank you for another great video. I appreciate the dense information and related pictures, which are very helpful to visualze that given information. Please keep on making such videos.
Regarding the russian doublescrew: may I suggest another reason for the damage on the trailing edges of some of the blades? I think they are caused by cavitation. The notches are forming not on the outermost points of the blades but at the point where the waterstream most likely departs from the surface of the blades. The little bubbles which are forming when the screw is cavitating do not create noise only but are also ripping constantly on the surface of the propeller. I'm not sure about the metal finishing of russain screws after casting, but I highly doubt that those parts were not polished out for leaving as few points of attack for those destructive elements as possible. So if you look at the blade under the right damaged one, the one which is lighted the best/reflects the most, you can see that the surface of the blade gets more "freckled" to the outside of the diameter. The trailing edge here seems a bit uneven but shows no notches on the edge at all.
All hail the king of subs !
15:38 in a gas turbine these stators may be referred to as inlet guide vanes
just thought of something..... I am assuming the submarine can go in reverse obviously not as efficiently but then they would no longer be inlets ... lol
One development I would expect to see is something already used in some helicopter tail rotors. Unevenly spaced blades. When designed properly this reduces greatly the noise caused by the blade hitting the wake of a strut or of the preceding blade, but I suspect they are optimized for a specific RPM regime.
Car tire water-dispersal grooves vary quite a bit in width, you might be surprise to look at one. They used to be all the same width on a give tire (e.g, a groove every 2cm or something) but that creates a strong energy at one specific frequency which is an annoying buzz or drone. The varying groove spacing creates the same amount of energy but spreads it over a lot more frequencies, creating "white noise" more similar to a wind sound. I'm not sure if this has any useful parallel in propeller design.
Perhaps they already do. A reason for the shroud as someome might take a peel at the impeller, stator and nozzle design.
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Fan blades on many newer cars are often done this way as well for the same reason.
Fascinating video. I was a submariner in the Cold War era. Very familiar with many of the older designs.
Well done . I grew up in New London Ct on the Thames River directly across from General Dynamics Electric Boat division with the Navy Sub base just up the river . Seeing subs go by in a almost daily basis was what we grew up with . I ended up working “ the boat “ from 1978 thru 1978 . Anytime we had a sub in dry dock the propellers were always shrouded and those were truly some of the most “ black art “ aspects of the entire machine . Even to this day whenever I am on the water in San Diego i see the props covered at the sub base facility they have there . There is similar science applied with torpedo props as well by the way . Thanks for the excellent explanation .
I was a Navy Diver stationed on an ASR, Sub rescue/towboat, homeported in Charleston. We had to take over the work for the ASR homeported in Groton while it was drydocked. We pulled in during a winter trip and I saw the local Navy Dive boat tied up alongside a sub.
When we left the next morning, the tugs that assisted us getting underway and in the river channel had broken thru a layer of ice that had formed on the river overnight. As we passed the sub with the dive boat, there was a diver with a big iron pick bar bashing a hole in the ice so they could dive. In an instant I resolved to never, never, ever, let them station me in this frozen diver's hell.
I've seen, cleaned and inspected most of US screw types, except the pump types as they showed up after I got out. I ran the first ever waterborne screw change on a Trident.
I probably passed you on that frozen winter morning. Hooya!
@@careyrose6059hey Carey. When were you in Charleston? I was on Orion from 73-78. Trying to remember the ASR we had then, I think it was Petral if I recall correctly.
Individual replacement blades would be an excellent way to change "identities" of subs
Every change in blade would change the subs acoustic signature.
There is a lot of other noise that they make aside from only the screw, so that would be like putting on a wig, might work for a short while at a distance but would soon be identified and cataloged as the new signature for that particular sub.
This was great. First time I've seen actual pics of that nine bladed screw the earlier RN boats had. Glad to hear the _Courageous_ museum is actually happening too. Shame it couldn't be _Conqueror_ though!
isn't the Conqueror to contaminated for the the public to be allowed to walk round in?
@@tommyfred6180 Oh I'd not heard about that. Is it a radiological problem or chemical?
@@rosswhite-chinnery5725 i have no idea and i would suspect its probably classified what the problem is. but she was and has had for along time a contamination issue of some kind. she was supposedly known as a "sick boat" even when still in service.
@@tommyfred6180 No. Courageous just happened to be the best condition boat as far as I’m aware.
@@tommyfred6180 Didn't know she had that reputation. Sounds like she was "that" sister in the class. There's always one!
Im so glad you decided to start a channel Sutton good for you buddy.
Sutton when you say you dont think we will see a worm drive in the future, are you referring to the MHD drives such as the ones fitted to Yamato 1? (probably a dead end as quiet but not very efficient energy wise) or an Archimedes Screw (called a worm drive in mechanics), which some small boats use due to higher damage resistance/less chance of fouling and better acceleration. I think with the advances in electric propulsion mounting motors outside the hull these may possibly have a future due to their extreme efficiency and more compact diameter allowing fitting to the sides of submarines.
It was a reference to Hunt for Red October
I too wondered what he meant with worm drive at 19:39. A worm drive is a certain kind of gear and has nothing to do with propulsion. My guess is he mixed it up with what is called caterpillar drive in the film The hunt for Red October (maybe also in the book) which is the fictional name there for magnetohydrodynamic drive like that of Yamato 1. Worms resemble caterpillars so that might have caused a slip of tongue.
@@HISuttonCovertShores With as little as i know about the subject I am glad I caught that reference lol.
I guess what we are talking about here is a pump inducer. These are good for achieving a significant pressure rise with good margin to cavitation. You often see them employed as a pre-stage (before a conventional centrifugal impellor) on rocket engine turbopumps where the power density is huge but cavitation must be avoided. Thing is though, for submarine propulsion what we want is a high volumetric flow-rate device with little pressure rise, not the other way round. So I don't think you'll see them employed here.
@@n2b998 Like on a torpeodo (aka) The Bedfors Incident? Anyone? Does anyone believe the Bedford Incident occurred? In some form or another?
Excellent, thank you! I have painted many a model, and not fully understood the various designs, and now I do. I wonder if the designs vary also based on the primary use being blue-water vs littoral? Do you think they could design the propulsion to be in-board, kinda like a jet-ski uses?
17:28.
Pump jet system is similar to jet ski
jet skies are extremely noisy pumps
The secrecy about pump jets has more of a historic reason. The design principles of pump jets are pretty much universally known nowadays and can be found in textbooks. They look pretty much like a single axial compressor stage of a turbojet, with slightly different blade design to adjust to the fact that water is much less compressible than air.
The blade ratio of rotor to stator blades is a tiny secret left, that defines the acoustic signature of a boat, but... there is a very limited number of reasonable combinations available that all naval engineers will figure out very quickly.
It's actually an axial flow water jet like in high speed water craft. The priciples are quite well known but the secret sauce would be the impeller/stator design hence the coverings.
@@shaider1982 Well, yes. Pretty much the same in other words.
These videos make me consider the engineering behind these things. What an awesome job.
I very distinctly remember the International Bruhaha when 2 Japanese Companies - 1 selling the actual machining equipment, and the other selling the computer control systems,
(remember, this was very early in the CAD/CAM era) between themselves sold the USSR all the equipment necessary to manufacture submarine propellers to US/NATO standards.
Reviewing what you have learned and learning anew, you are fit to be a teacher.
I’ve also heard about a so called “caterpillar” fitted to a modified Typhoon…
The captain was some Scottish guy
Outdated info, we all know that sub was lost in an accident in the Atlantic!
Magneto hydrodynamic (MHD) propulsion systems? Really bad cryogenic plants, susceptible to damage by goddamn cooks. 😏
Magneto Hydro Dynamic propulsion…sounds like whales humping.
I believe they went down when they were going to conduct miss isle drills while listening to rock and roll
Really learned a lot here. Thanks for putting this together!
For the "future" (the outside driven Pumpjets) I'd say there might be one additional huge benefit that it might allow direct electrical drive without gears because the motor diameter is huge, ideal for the required torque.
But woulodn't you still need some sort of gearing to turn Battery electric power into mechanical power to power a submarine? Example Washing amching motor to drive a train car
Do Tesla cars use gears ?
@@rayRay-pw6gz yes but but Teslas are powered by batteries, and anything that can generate enough electrical power to run a pump jet like that is going to have a nuclear reactor
@@Laotzu.Goldbug I agree with you on the power plant on a submarine. But, the line of thought was the removal of the gear box . The motor and pump jet are on the outer hull. No main shaft thru hull.
A real person speaking? Thank you for your good work. 😎🕊🧡
thank you for this video Mr Sutton! I learned a great deal! and i will be applying this to my RC submarine builds. I have a 50" Virginia in the works right now that will benefit from this video.
Sounds like a cool project. I know that in scale model airplanes they can't generally fly them with scale propellers because air molecules don't get smaller when you shrink the plane down, but I suppose a scale prop on a sub would just underperform, not fail to work completely.
@@AlRoderick scale props do work on subs decently. However I 3d printed a custom one that’s more like an impeller so we will see how that works once it gets a bit warmer where I live. Too damn cold to primer and paint right now
Really liked this format sir,
As we need more of the explanatory videos for the amateur audience.
Most interesting topic!
Any submarines that used different sets?
(I'm thinking of one style for silence and another for speed)
A lot of Soviet boats had small electric thrusters on their stern planes, but I believe these were more for maneuvering than stealth. In fact I am pretty sure I've heard that the "spinners" were actually noisier than the main propulsion (probably because they operated very high revolutions).
I do recall reading in one source a long time ago that the early Soviet nuclear boats like the _Novembers_ and _Hotels_ had electric "creep" motors but these seem to have been an alternative means of driving the main propulsion at low revs rather than being shafted to their own separate set of screws.
Very good video. I learned quite a bit about sub screws. Thank you for that.
First-time watcher. Nice format. I do audio software and am puzzled how it could be that prime-bladed blades have anything special about their harmonics. Any propeller etc. should have a base frequency of the time for 360 degree rotation, with a very strong harmonic at the number of blades. Then that harmonic would itself have many strong harmonic, due to the "swoosh" of the blade going by not being a sine wave. The base frequency would be nearly zero audio strength unless the blades differed (accidents, damage from cavitation, uneven spacing, etc.) But I don't see how say a six- and seven-bladed propeller would have a drastically in any of this. I sensed some hand-waving when the subject came up and would like a more specific explanation.
What he referred to as harmonics is not the harmonic frequency of the screw itself, but how it can cross or harmonize or reinforce when other basic frequencies like 2 or 4 per 360 also exists… if you want to know where 2 or 4 per 360 came from, look at the number of rudders…
@@Skyshade nope, still don't follow.
@@Skyshade Blade designer for sub must try the "frequency. cancelling system" in reducing noise...Its has been an 80's decade technology: A noise detector will identify the noise frequency number, then the computer will generate a duplicate negative frequency - to cancel the existing noise. Another idea: The substance used by fast swimming fish should be identified - then alloyed to the molten metal of the sub propeller during moulding....Also try to put some boron as alloying additives....The Bible said in book of Ecclesiastes 1:9-10 "There is no new new things under the sun..."...you cant invent a new things,everything has been existing already- all scientist, inventors,designers,etc to do is to imitate God engineering, principles, system,etc found on His created animals,fishes, birds,plants,micro.organism,others creation.... Such Biblical fact is one of many secret of Israel why they are very efficient and prolific when it come to inventions,designings,etc
I found this on Quora
(based on this comment I believe "odd" is the the right word to use more than "prime"):
The first nuclear powered Albacore hulled submarines had five bladed screws of conventional profile. As the conventional profile propeller blades passed from disturbed and back to undisturbed flow, the propeller blades would flex longitudinally, emitting “blade rate” acoustic energy. To reduce the emitted blade rate acoustic energy, two changes were made to the screw:
1) blade profile was changed from a conventional shamrock leaf shape to a skewed, banana shape - this reduced the blade flexing by having only a portion of the skewed banana blade cutting through each disturbed flow region at a time, stretching out the transitions through the different flow regions to reduce blade flexing.
2) number of blades was changed from five to seven, to reduce individual blade loading and thereby individual blade flexing. An odd number of blades is used so that only one blade at a time will be going through the disturbed flow area behind each of the four control surfaces. A very secondary effect is that for a given shaft RPM, the blade rate of a seven bladed screw compared to a five bladed screw results in greater acoustic energy attenuation (the slope of the attenuation/frequency curve is roughly 7 dB/decade per thousand yards)
@@lqr824 - Like you, I was puzzled by why a prime number of propeller blades should be so significant, and following the same rationale as you provided. The explanation for selection of number of blades probably lies in the response provided by Skyshade and a few other posts in response to this video. So if you stuck a 4 blade propeller behind a typical set of 4 planes at 90 degrees separation, that would be a bad idea due to interaction of the blades with the wake field. An 8 blade propeller would probably also not be ideal for this case. Not that I know of any submarines that only have 3 equally spaced planes aft, but if you stuck a 3 blade propeller (a prime number) behind them, that would also be a bad idea, as would a 6 blade propeller.
A wonderful piece, as always, Mr. Sutton.
There is a good reason for SSK's not to have a pump jet and its the same reason that merchant vessels don't have Kort Nozzles ( a pump jet is simply a very very well engineered type of Kort Nozzle ). The reason is drag , the nozzle/shroud is heavy and produces a fair amount of drag so merchant ships ( even the largest ULCC oil tankers ) have an open propeller as it uses considerably less fuel for a given speed and allows the ship to have a faster cruising speed. On fishing boats only those that tow gear ( trawlers/beam trawlers/scallop dredgers ) have Kort Nozzles as those work at far higher efficiency at medium RPM but low hull speed ( you get about 35% more bollard pull from a well designed Kort Nozzle than an open propeller so when towing gear it saves a lot of fuel which over a year means large fuel savings even considering transit time steaming to and from the grounds ). Those fishing boats built to fish static gear ( pots / gill nets / longlines ) only use an open propeller as that saves them a lot in fuel over a year due to not having the extra weight and drag of a kort nozzle set up
What do you do for a living if you don't mind me asking? I have been building and repairing ship and tugboat propellers for 25 years and I have nothing to add to your comment is why I ask. I've built and repaired propellers from Aircraft Carrier size on down to impellers on Seadoo's.
@@mikebrase5161 I'm a retired ( knackered back sadly ) Fishery Scientist, I was a commercial trawlerman before that. Always been interested in how to use less fuel for a given speed/bollard pull and advances in the design of modern fishing boats means you can build a boat of more than twice the displacement on the same length with a larger engine and use less fuel overall , the new kort nozzles are now around 40% more efficient than an open prop when towing gear at 4knots. A Kort system does cost a lot more than an open prop but trawlers will see fuel savings meaning the nozzle pays for itself within 3 years
@@DavieTait I did something you might find interesting. I took all of the specs for the Queen Elizabeth class Battleship I got lucky when I came across the reduction gear ratio used. I wanted to see how much we could raise its not speed with modern Prop styles. With a modern 5 Blade High skew which was a fairytale back then, the speed increase was 4 knots without a loss in Fuel efficiancy which if I remember was around 80%.
I've worked inside more Nozzles than I can count. They were definitely a game changer especially for the Push/ Pull Tug boats which is mainly what I work on currently. The company I work for has built the majority of Tug props on the Mississippi river. My favorite is at least once a year we have to send a tech out to recut the Diameter because a customer will measure the outside of the nozzle not taking into consideration the taper to the inside dia. We even have it in Red on the spec sheet for customers to fill out when they make the order. I had to fly to Tonga before Covid it was awesome hahaha. Best customer paid vacation ever.
Good additional info about Kort nozzles. I had the intuition about this, but you gave the right words to explain it better noting drag.
Maybe not mentioned but a very basic statement would be Kort nozzles are best for high thrust needs. So Towboats. Modern port towboats have azimuth thrusters for maximums maneuverability and maximum pull. As you said.. they move slow but move lots of water which the Kort nozzle is good for.
Another thought, there is always a single ideal speed and rpm for a propeller, so the choice of propulsion has to take into account a usage profile, maximizing operating conditions and their frequency and importance.
Davie Tait: I would have commented much the same as you on the matter of pump jets / ducted propellers and their use on SSK's, but as far as I am aware from what was in the public domain, the now cancelled Attack Class SSK's intended for the Royal Australian Navy would have had pumpjets fitted. I am left to wonder whether the prospect of a lower signature would have come at the cost of reduced underwater range / endurance compared to an optimised open propeller?
Enjoyed that bit of education quite a lot. Thank you and well done.
great video man i love your content and i love your website (its one of my bookmarks on my toolbar :))
Refreshing change from the normal video that, as an example some guy showing a lake and all you see is a face. This is a learning experience and thank you for that. I was in the USAF and know nothing of submarines. Now I do, thanks.
Thank you, your videos are so interesting. My Dad would have loved watching them, unfortunately he died before the internet age. He was the senior test Engineer for the UK nuke sub program in the early 60's, after getting trained in USA in Pennsylvania. Your videos would have been totally followed by him, and no doubt added to with commentary.
This chan should have 500k subs with the right production
Nice work, I really enjoy all of your videos.
A thought on the dubble screw and your comment on the damages on the blades.
I believe that the damages on the edges of the dubble screw is wear from cavitation.
I'm certainly no expert in hydrodynamics but I do know that cavitation is the result of too low pressure at the trailing edge of the blade which certainly seems to fit with where the damages are located.
With a dubble screw setup, the first screw blade will be more susceptible to cavitation issues than with a traditional one screw setup as the next set of blade will decrease pressure between the screws, thus making it even harder to avoid cavitation.
Of course the offset of the two screws will mitigate this issue but I can't but think that at some speeds (accelerations) the trail of the first screw will line up with the second.
This is where the counter rotating screws come in 😉
And the Russian engineers 'proofed' that concept for us, iss potato! (doesn't work)
to be fair, i found this by accident.however i decided to watch it and i actually learned something worth knowing today. great informative video. thankyou. now subscribed
Red October in the movie used Magneto Hydrodynamic Drives (Caterpillar Drives they called them). This is a drive technology with no moving parts as it relies on moving the water with magnetism. It's actually a real technology but not very efficient if I recall correctly.
Yup, see the Yamato-1 testbed vehicle. Was slow speed. Perhaps with new super conducting magnets, this might become practucal.
@@shaider1982 true the weakness of super conductors has been their need for cryo cooling. Recent advances have brought them temperature up significantly.
That is the best "unscripted" video I have watched. Well done!
This was very informative and frankly quite interesting. Thank you so much for this content.
A video or article about the concept submarines of Naval Group (formally DCNS) would be really interesting.
Between SMX-21 and SMX-31E (shown at the end of th video) they had a lot of creative and differnt ideas.
"People don't want you to see inside it... So let's look inside it." 😬👍
And lo, a subscription was earned!
Something I've not seen here is any mention of unevenly-spaced blades. I remember asking my Dad why the cooling fan on our Ford Cortina had the blades unevenly distributed around the centre. Dad (who is an engineer and used to be editor of OEM design) said that it was to mix up the frequencies of sound produced and to avoid producing a more noticeable constant hum of a specific frequency for a given engine speed. Given the the key to propulsion in a submarine is stealth, has this concept not been tried on submarines?
I think this was touched on when he mentioned skew-back screws having prime numbers of blades to avoid getting a harmonic resonance. You might be able to reduce this even more by having unevenly spaced ones but you would likely significantly reduce the efficiency of the submarine without a commensurate decrease in audible signature making it worthwhile. Since the radiator in your car doesn't have to worry too much about efficiency, and the subjective noise quality is all that matters, it's a good trade-off in that case.
Also, I'm not entirely sure so an engineer can correct me if I'm wrong, but I think that in unevenly spaced propeller would create uneven propulsion, requiring a constant steering correction just to go straight. Obviously this is not desirable on a submarine.
Ducts are there to prevent wing tip vortex which creates cavitation.They also camouflage noise source.On submarines any type of vortices are not acceptable they create noise and drop performance.Screw backs are built to prevent wing tip vortices as well. Center of propellers turn slowly while tips of propellers turn at high speed.So foil thickness to chord ratio must be different for efficiency.Higher the speed longer the cord to thickness ratio and higher rake for preventing cavitation performance.Note there are more rake at tips.I am a speed sailor on windsurf so I have spend much time searching fin designs for speeding.New propeller blades are basically twisted fins or foils with asymmetric foil shapes.I shape my fins asymmetrical they do perform better on one way starboard or port ride.I like pump jets they will get better by time ducts will help protecting blades against shocks as well.Counter rotation duo props are good on performance by straight flow instead of vortex flow but counter rotating blades may create more cavitation because of sudden flow change.
This might sound weird but this video reminds me: Have you thought about doing a video on the submarine from SeaQuest DSV? If I recall it had some really unusual but plausible technology at work.
Many thanks for this great content. Any chance you will do a feature on the Cosmos midget submarines?
Any chance for a video about the structural considerations of the submarine?
E.g. pressure, width to beam ratio, internal frame, do they study things like resonance frequencies of the rooms inside the ship while it's being designed, or there's so much stuff that it's not an issue?
A resonance problem nearly pulled the Nautilius apart on its return from a round the world cruise about 70 years ago.
Eliminating a bump on the lip of ballast tank opening beneath the hull turned the tank a police whistle at high speed.
Also, cavitation occurs during high activity -- like a hickey;
Hi, Great video. Really interesting. No rubbish music. All pictures identified rather than most which use random anonymous pics. how does the sycle blade cut the noise? I understand large slow turning but......
Interesting with the side mounted ring driven on the rim what kind of thrust bearing would be used?
An excellent presentation. Great talk on a very interesting topic.
Thank you for giving me a research term!! I've seen "Annular Screws" on submarine models, or pictures of models, but I never knew what to call it to learn more about it or why it ever existed in the first place. Most of my knowledge comes from airplanes, so my only guess is that the ring is meant to prevent tip-vortices from generating, but as it seems to be rare, and to even have gone out of fashion, I'm guessing it didn't work?
Some LA688Is use/used an annular screw. Not sure if current, but certainly in the late 80s/early 90s was introduced. Proposition was that the connecting ring eliminated tip vorticies and reduced blade flex. Sometimes also called the "ice ring" screw (at least in USN service), and might have had an additional functional use for boats working in icy waters as a means to presumably protect against tip-strike.
LA688I annular screw image: www.mulsannescorner.com/models/Submarines/LosAngelesclassSSN/01.jpg
I remember relieving the throttleman for a head call during a northern run and answering bells concurrent with a call from up forward with the instruction to answer all bells until cavitation is noted after which additional turns shall.not be made. Exciting run that one.
Do pumpjets foul easier than non shrouded propellers, or is fouling not a big issue for submarines?
Ducts may foul faster I guess.
No, when a submarine enters dry dock, and sometimes if a boat is in a hard running period (sea time, and even more sea time) the boat below the water line will be cleared of weed and such, particular attention is given to the screw or propulsor. The boat will use its own divers to carry out this task OR if CDs (Clearence Divers, underwater bomb disposal experts, these guys are totally insane - and exceptionally highly trained and their courage is not in doubt) are available then they'll come along and 'dive on the boat' while alongside. If the boat goes into dry dock (about once every year, ish) then the whole boat is scoured of marine growth, old paint is 'harben gunned (think a patio washer on steroids) away from the pressure hull, then 'chocolate coloured "admar" (ADmiralty MARine) paint is applied, when dry the whole shebang is painted a cheerful 'losheen black colour' (it goes on shiny and drys to a cheerful dullllllll black).
Measurements are done on the propulsor to check that the rotors inside the duct are within tolerance to avoiding touching the shroud. The shroud was known to move now and again (the whole unit was VERY heavy).
Once all work was compleat, inside and outside, the dock was flooded up, the boat moved back to a tidal berth and after a VERY, VERY intense work up, usually taking two months from start to finish, the boat is passed fit to go back to frontline duties.
For us that meant back where we truly belonged - inside their back yard and mixing it with the big boys!
@@petewilliams.1122 Thank you Pete for your comprehensive reply. 👍
I'm on holiday right now on the Isle of Cumbrae (Great Cumbrae at the end of the Firth of Clyde) and a few of days ago there was a lot of coming and going from Faslane Naval Base. I saw a Dreadnought class boat, a Los Angeles class boat, but I'm not 100% on either, a destroyer and at least two helicopters. The American submarine was visiting Faslane according to a friend who works there, but with all the commotion I wonder if it was a bit more than that. There's talk of Russians and Western undersea assets. We'll be able to read what's actually going on in a few decades. We're definitely in the Second Cold War, but just like the First, people won't accept it for a while.
I hope that you enjoyed your time in the service and I do appreciate it. "in their back yard" sounds great. 👍
Look after yourself.
"this is my drawing, its not very good"
The drawing, made in paint:
*detailed and perfectly fine infographic of a rare type of screw*
I find it interesting that flip the skew around and we get basically the history of computer fans. Look at a Phanteks T30, Noctua a12x25, Arctic P12, or some Zalman or Asus annular gpu fans. The reason is exactly the same: lowering the noise.
NO 12:48 I WAS INTERESTED
man I love your videos. now I will not die happy unless I figure out what info you were about to provide. I used to hate subs. now I love em, watch these all day at work. thanks boss
Have you done a video yet on bottom crawling submarines ? I seem to remember hearing that they were virtually immune to most forms of attack.
interesting suggestion
I don't believe anything in the water would be immune. Water carries sound way farther than air. Granted if isothermic. But even if there was a temperature chamge and the sub hid below it. We would still drop a temp bouy to get that reading to find it
@@stevenc8140 I think it's like air to air radar guided missiles don't have the ability to attack ground targets , because they don't have a way to separate the target from the earth . So torpedo don't don't work and old fashion depth charges will move the entire mini submarine instead of collapsing the hull. So you can find it on side scan sonar but you can't attack it and it can still attack you.
@@robertlackey7212 hey thanks for the info!
@@stevenc8140 Your welcome
I love these insights you are giving us. thank you!
All I can think of when people talk about pump jets is the Australian politician in the defence committee a few years back.
Yeah classic
That would be Senator Pauline Hanson who has been making her own, shall we say "interesting" contribution to the political discourse of this great country since 1998.
(Stints in jail and on _Dancing with the Stars_ notwithstanding.)
The props amd shafts are also hollow, and filled with fine sand and light oil, to help dampen any noise that *is* generated.
I found it interesting that the number of blades had to be a Prime Number to reduce vibration. Go figure!
Untrue.
I just watched a 218SG return to Kiel harbor from some kind of sea trial a few weeks ago, cool that you used it as an example here!
I worked in Kiel a couple of years ago. Could see the Subs come in from my office. Sometimes one of them was playing the pirates of the caribien theme on speaker when sailing in with crew on deck, (if i remember correctly).
@@theacme3 oh like in the beginning scene of the first movie? That's amazing
so back in the early industrialized wars, mainly WW1 , surface ships used various paint schemes to thwart visual targeting and identification
i wonder if there is an analogy here for the sound signatures of submarines, for example varying the pitch of the static blades, or having an independently rotating vortex diffuser
or perhaps even changing the mechanical properties of internal components to alter the acoustic signature of the propulsion, such as bearings which can be repositioned along the length of long shafts, or mounting machinery on dampeners with adjustable tension and stiffness, which could all be actuated electronically and simultaneously so as to obfuscate the submarine's identity, or perhaps even configured in a specific way to mimic another craft
One technology used to reduce sound outside submarines is frequency smoothing. If you have something that makes sound, you deliberately mismatch the parts that make the sound so that they don't sync up. For instance, a tyre tread is made in very uneven arrays, so that the sound generated isn't in one frequency, but across many frequencies. That means that in any frequency you are hearing in, the decibels is much lower.
I'm not sure if the secondary blades are all matching perfectly in a prime series or of they also arrange them to be mismatching and breaking up frequencies.
RaDAR and SoNAR absorbing materials are cutting edge tools in the ongoing naval arms race.
Fascinating. I have a friend, but he is very opsec oriented. My memory is, "do not cavitate" 50 years ago. LOL thanks fo rposting.
Interestingly the centreless propeller was being used in a experimental seabed electrical generator in the Bay of Fundy.
This is awesome, was always fascinated by the technology behind these
Wow, waaay too long between videos. I’d like to see a video on nuclear submarine detection. Most notably that nuclear reactors specifically release nano particles called anitneutrenos. Many tests have been done to detect anti neutrenos. To what capacity is it feasible to employ these devices to detect nuclear submarines?
Our college Radiation Physics professor said neutrino was very penetrating,any thickness of lead,heavy metal,etc is nothing to its penetrarion power,it can easily pass.thru....So maybe it produced a mutant,abnormally behaving molecules of flying submarine wall materials,also of sea water outside of submarine- thus,if a detector can be invented, all nuclear powered submarine will be tracked in the long run
@@fortunatodeguzman8017 absolutely. Electron-antineutrinos are abundantly produced by the nuclear fission reactions inside the reactor cores (6 νe are produced in the uranium fission induced by neutrons [Way48]). A typical ~ 1 GW standard nuclear plant radiates about 5.1020 antineutrinos per second; their energy spectrum extends to 10 MeV and their mean energy is around 4 MeV. So quite a lot of detectable energy being emitted. The game has changed
@@MrSubmariner76 Neutrinos are notoriously hard to detect.... they carry no electric charge so they have to hit matter that can give off a charge...and the chance of hitting another particle are slim. Is the energy you are mentioning the amount typically released upon hitting another particle or the amount of energy related to its mass? Also, a sub's reactor would be what, 1/20 or 1/25 at speed of your 1 GW reactor?
Maybe electric driven rim pumpjets, could be fitted with deflecting horizontal and vertical fins at the end of the tube ducting channel, plus fitting upto three or four rim pumpjets being installed.
With four rim pumpjet of them fitted around the hull, spaced at 90 degrees apart either above and below plus on either side of the hull?
Or four rimjets positioned two on either side of the hull, but on near the top of the hull and the other near the bottom of the hull on each side of the hull.
Or just three rim pumpjets spaced out 120 degrees apart, but with these rim pumpjet propellor blade, actually having a double or triple propellor blade layout, with 5 blades, then a set of 7 blades plus 11 blades?
Also using replacable interchangeable compsite-alloy blades, with these blades maybe coated with a ceramic layers, to protect the blades from damage and from corrosion too.
Or maybe in the future submarines and surface ships, will both be fitted with multiple rim pumpjets in a series within an extended ducted housing, along the side of the hull for upto half or three quarters of the hull length, to create a very silent and quite propulsion system at high speeds?
In way creating a worm drive like system, as suggested in the novel Hunt for Red October.
Very interesting stuff from the more (well, more than the average) technical side of things. Very good explanations of stuff that's somewhat secretive. I'd love to hear something about the Toshiba-Kongsberg scandal - which saw Western-aligned countries funneling CAD/CAM equipment to Russia to help them make quieter propellors.
A very interesting video of a topic that is shrouded in mystery!
Glad you enjoyed it. I should have used that pun!
@@HISuttonCovertShores Oh Gawd! I didn't even realise that I made that pun. Must have been the hIeat, hot and muggy, 30 ish degrees C.
I'm curious what is the fastest non-nuclear powered submarine currently in service? And will we see Pump-jet be viable in higher speed conventionally-powered submarines?
They call them “ The Silent Service “. For a reason . Submarines built for war need to be undetectable first and foremost . Speed not as important .
Excellent submarine video, I learned a lot. Thanks.
What about having a pumpjet inside the hull itself? So you have an intake or multiple towards the from of the sub, that water travels through a system of pipes to the pumpjet and is then expended from a long tube towards the back. Obviously that'd take a ton of space but it would reduce the noise quite a bit, in theory.
I'm sure it's totally impractical but I think it's a neat idea.
Reason iits not done is because like ordinary props the bit that creats to biggest noise is in fact tbe water boiling on the very edge of the blade due to compression, the same thing happens with a pump net so this is why its not done.
There is a way round this but is so fundimentally different that it has yet to be tried, that is to have the intake at the front of the sub so that the sub itself absorbs much of the noise, also from a damabe control outlook it would be a real headache.
This was very interesting, thank you!
Great video on a fascinating topic! I wonder what design choices led to the 212 screw having squared off tips? Or was it a trick? lol
It's not a clear photo and it's difficult to make out the sickle shape. I wondered if it was an attempt to stop tip-vortices by bending the tips over, like with aircraft "winglets". I'm sure blade "winglets" would have been tried but, apparently, not successfully.
Great info 😀 thank's....Do these exsist for yachts too ?
Interesting. I am a retired US Navy submariner. I remember the screws well. I recall being told that the number of sickle blades on the screw was classified. There were seven. I always thought that ridiculous since the floating dry dock in Scotland was open at both ends. Even with the screw covered by a shroud, all anyone needed to do was count the peaks on the shroud.
Did you just leak classified information?
@@parallax9084 I highly doubt it. If you notice in some of the more modern submarine movies, the screws are frequently depicted with seven sickle shaped blades. There's also photos of submarines all over the place im drydocks where the screw is plainly visible.
@@robr2389 is there any classified information you would tell me?
@@parallax9084 No. Nothing that's not already publicly available.
@@robr2389 Unfortunate. I wish you luck, goodbye
Awesome. Enjoyed the video very much.
Allow me to correct a couple of errors. The first of class HMS Swiftsure, and first of class HMS Trafalgar both had nine bladed screws. The rest of the S boats had pump jet propulsors. The rest of the T boats had pre swirl pump jets or PSPJ, ( I am not allowed to quote the number of blades or rotor design because of the OSA).
Further... NINE blades does not equal frailty or anything like your suggested weakness. Both Swiftsure and Trafalgar had great success with their very robust 1X9 fit with superb low revs equaling very low turns per knot or TPK. With hardly any revs on at all these boats would fly. Both 1X9 screws were gigantic, 20 feet in diameter and at the time they both had the lowest TPK in the world (I know of what I speak).Becsause of the size of the screws both Swiftsure and Trafalgar were fitted with BIG rudders, the follow on S boats had small rudders. ALL the T boats had big rudders. Both screws were made of nickalium and were true feats of engineering. With exceptionally low revs came the advantage of being able to have an excellent reduction ratio of engine to shaft (once again I am not able to quote numbers because of the OSA).
On one occasion during my time on Swiftsure we needed battle short revs astern, we dragged THREE ocean going tugs 100 yards astern with us, the ocean going tugs bully supertankers in their day to day lives, they felt the raw power of an S class SSN that day.
One another occasion we needed full ahead revs to get out of a situation faster than we got into it (always have that ability). In no time flat we exceeded thirty knots and we were NOT cavitatting!!!! Like I said, these screws were GIGANTIC±
HMS Churchill was the first SSN in the RN to have a pump jet, Once the design was proven she reverted back to a screw.
Once the USA saw that prolusors were not going to fail drastically and that the Brits had made them work then they wanted in. PSPJs fitted to the T boats were and are still exceptionally quiet. I expect the same to be said of the A boats and the bombers.
I hope this has been informative. 👍
Thanks, yes good info.
Was aware re first of class having the screw, just not going into so much detail in a video. Re fragility, interesting. But have got the frailty from somewhere.
You might like my article and cutaway of the T-boat. Not intended to be 100% accurate for very obvious reasons, but hopefully captures the feel. Also, mix of individual boats in internal arrangements. www.hisutton.com/Royal-Navy-Trafalgar-Class-Submarine.html
@@HISuttonCovertShores The T boat accommodation ladder (from the main access hatch to the control room), the first nine feet or so is straight up and down fore and aft, and then (the next six feet or so) slants to starboard, well it was when I shipped out on the black pigs! I remember showing some former German U boat captains around. When told that at the bottom of the accommodation ladder they were already fifteen feet underwater, their eyes became wider and wider, I heard a genuine comment, 'what could we have done with one of these...' I'm sure they were all contrite National Socialists!
When they saw the bomb shop however...