# Submarines vs whales vs fish: are propellors more efficient than flukes or tails? **URL:** \ **Category:** Factual Questions\ **Created:** [May 7, 2012, 12:22am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111 "2012-05-07T00:22:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 7, 2012, 12:22am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/1 "2012-05-07T00:22:56Z")
Submarines have propellors; whales have flukes; fish have tails. Which is the most efficient? And what about quietest and least-easy to detect? (I’m not sure if there are any fish large enough to really count, even if you include the whale shark.) ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [May 7, 2012, 1:02am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/2 "2012-05-07T01:02:58Z")
> [@Quartz](#): > > Submarines have propellors; whales have flukes; fish have tails. Which is the most efficient? And what about quietest and least-easy to detect? > > (I’m not sure if there are any fish large enough to really count, even if you include the whale shark.) I thought penguins were the most efficient. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 7, 2012, 2:01am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/3 "2012-05-07T02:01:49Z")
I’d expect flukes and fishtails to be about equivalent, since they’re basically the same thing, just turned on its side. As for either versus propellers, it depends on what the thing they’re driving is. A flexible-tailed submarine would be an engineering nightmare, and likewise a free-spinning propeller would be an evolutionary nightmare. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 7, 2012, 2:36am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/4 "2012-05-07T02:36:46Z")
> [@Chronos](#): > > As for either versus propellers, it depends on what the thing they’re driving is. Are we not able to measure the noise, energy, and other efficiencies of a whale’s fluke? > [@](#): > > A flexible-tailed submarine would be an engineering nightmare That’s for another thread. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [May 8, 2012, 1:24am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/5 "2012-05-08T01:24:02Z")
I’ve watched several PBS shows where some college puts on a challenge to design a better sub propulsion system. Invariably many entries feature some form of mechanical fin or flipper. At one of them a Navy egghead basically dismissed all of these entries as fancifully impractical, that it’s been proven long ago that a rotating propeller is by far the most efficient marine propulsion method. It’s similar to the wheel. No life form has evolved one, but on a reasonably smooth surface its the best transportation system. ---
**Author:** ![Gagundathar](https://avatars.discourse-cdn.com/v4/letter/g/a183cd/32.png) [@Gagundathar](https://boards.straightdope.com/u/Gagundathar)\ **Post date:** [May 8, 2012, 1:29am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/6 "2012-05-08T01:29:20Z")
> [@kanicbird](#): > > I thought penguins were the most efficient. Maybe so, but they are absolutely the coolest things in the ocean. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [May 8, 2012, 1:35am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/7 "2012-05-08T01:35:25Z")
Modern submarines, I have read, are dead silent. Often described as black holes in the water. Mind you this is due to high tech design of propellers. I have a recollection of (I think Toshiba) getting into deep doo-doo in the 80’s because they sold hi-tech milling equipment to the Soviets which would allow them to manufacture silent propellers. Most propellers cavitate when spinning (they form little bubbles along the edges of the propeller which implode and make sound). Flukes and tails do not do this…whether the design prevents it or merely because they do not churn water as fast as a propeller does I have no idea (I am guessing the latter). A spinning propeller moves much faster causing the bubbles (hence noise). Super hi-tech submarine propellers these days do not do that. Or rather I should say are a lot less prone to it. IIRC if the sub goes to full power there is a point where there is no avoiding it. If you watch the movie _Hunt for Red October_ there is a scene where the American captain tells the helmsman to go to full speed. The sonar operator complains they are cavitating (making noise). Of course the captain knows this and it was his intent to make the noise to let the other sub know they were there. Till that though the other sub had no clue the US sub was near them. Movie I know but accurate as far as it goes for that bit. ---
**Author:** ![DHMO](https://avatars.discourse-cdn.com/v4/letter/d/ecc23a/32.png) [@DHMO](https://boards.straightdope.com/u/DHMO)\ **Post date:** [May 8, 2012, 4:41am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/8 "2012-05-08T04:41:51Z")
I have heard that when Tom Clancy was writing the book, \*\*\*[The Hunt for Red October](http://en.wikipedia.org/wiki/The_Hunt_for_Red_October), \*\*\*he used publicly-known “Popular Science”-type information about state-of-the-art modern submarine design, and extrapolated and filled in the blanks some. His information on top-secret propulsion technologies hit a little too close to home, some government agents came to see him, and he had a bit of 'splainin to do before they were satisfied that he had no access to restricted information. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [May 8, 2012, 5:11am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/9 "2012-05-08T05:11:24Z")
> [@DHMO](#): > > I have heard that when Tom Clancy was writing the book, \*\*\*[The Hunt for Red October](http://en.wikipedia.org/wiki/The_Hunt_for_Red_October), \*\*\*he used publicly-known “Popular Science”-type information about state-of-the-art modern submarine design, and extrapolated and filled in the blanks some. > > His information on top-secret propulsion technologies hit a little too close to home, some government agents came to see him, and he had a bit of 'splainin to do before they were satisfied that he had no access to restricted information. I forget the exact story but supposedly during WWII some story was published in a sci-fi magazine describing a bomb remarkably similar to an atomic bomb. As I recall the government freaked a bit and had people investigate. They realized it was just someone’s creative imagination and figured it would seem odd if the stories (the story was a serial) suddenly stopped for no good reason so allowed them to continue. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [May 8, 2012, 5:20am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/10 "2012-05-08T05:20:41Z")
> [@Hail\_Ants](#): > > At one of them a Navy egghead basically dismissed all of these entries as fancifully impractical, that it’s been proven long ago that a rotating propeller is by far the most efficient marine propulsion method. This was true for airplanes, too, until jet engines were developed. Could a marine jet be designed the same way, to be more efficient? I believe there are marine animals that move by jets rather than tails or flukes (squid, for example). > [@Hail\_Ants](#): > > It’s similar to the wheel. No life form has evolved one, I believe there are microscopic life forms (protozoans?) that have evolved a wheel form of propulsion. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [May 8, 2012, 5:37am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/11 "2012-05-08T05:37:03Z")
> [@t-bonham@scc.net](#): > > I believe there are microscopic life forms (protozoans?) that have evolved a wheel form of propulsion. Perhaps you’re thinking of propeller-type propulsion? As I recall flagellates are known to whip their tails around in a circular motion, effecting a crude propeller. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [May 8, 2012, 5:42am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/12 "2012-05-08T05:42:14Z")
> [@t-bonham@scc.net](#): > > Could a marine jet be designed the same way, to be more efficient? I believe there are marine animals that move by jets rather than tails or flukes (squid, for example). Significantly different, I’d say. Aircraft jets provide constant thrust, with (if I’m not mistaken) the intake air providing oxygen for combustion. Doing that with water is a whole 'nother proposition. Squid do it one squirt at a time via muscular contraction; I suspect a mechanism to do that would be terribly unwieldy. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 8, 2012, 9:20am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/13 "2012-05-08T09:20:20Z")
[Dolphins](http://jeb.biologists.org/content/185/1/179.short) have a propulsive efficiency of 0.81. Not sure what propulsive efficiency subs have. If you want a detailed explanation of the differences between swimming modes in fish read [this](http://www.mor-fin.com/www.mor-fin.com/Science-related-links_files/http___www.ece.eps.hw.ac.uk_Research_oceans_people_Michael_Sfakiotakis_IEEEJOE_99.pdf). Short version pertinent to the op: > [@](#): > > Thunniform mode is the most efficient locomotion mode > evolved in the aquatic environment, where thrust is generated > by the lift-based method, allowing high cruising speeds to be > maintained for long periods. It is considered a culminating > point in the evolution of swimming designs, as it is found > among varied groups of vertebrates (teleost fish, sharks, and > marine mammals) that have each evolved under different > circumstances. In teleost fish, thunniform mode is encountered > in scombrids, such as the tuna and the mackerel. Significant > lateral movements occur only at the caudal fin (that produces > more than 90% of the thrust) and at the area near the narrow > peduncle. The body is well streamlined to significantly reduce > pressure drag, while the caudal fin is stiff and high, with a > crescent-moon shape often referred to as lunate [Fig. 7(d)]. > Despite the power of the caudal thrusts, the body shape and > mass distribution ensure that the recoil forces are effectively > minimized and very little sideslipping is induced. The design > of thunniform swimmers is optimized for high-speed swimming in calm waters and is not well-suited to other actions such > as slow swimming, turning maneuvers, and rapid acceleration > from stationary and turbulent water (streams, tidal rips, etc.) ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [May 8, 2012, 9:59am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/14 "2012-05-08T09:59:07Z")
> [@Gary\_T](#): > > Perhaps you’re thinking of propeller-type propulsion? As I recall flagellates are known to whip their tails around in a circular motion, effecting a crude propeller. They don’t just whip around in a circular motion–they actually rotate on an axle. Hard to imagine the same principle working on a large animal, though. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 8, 2012, 10:25am UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/15 "2012-05-08T10:25:40Z")
A [relevant article](http://jeb.biologists.org/content/214/9/v.full): > [@](#): > > Do fish and jellyfish swim better than submarines? It depends a lot on what you mean by ‘better’. Some people have argued that fish are more efficient than subs, meaning that they waste a smaller fraction of the total propulsive energy. Others have argued that efficiency isn’t all that important; instead, it’s just the total energy that matters, regardless of what fraction of it is wasted. > > One major difference is that jellyfish and fish produce thrust in pulses, whereas propellers on submarines produce thrust more or less continuously. > > There’s good reason to suppose that pulsed propulsion (jellyfish) might be more efficient than steady jets (propellers). For example, pulses produce vortex rings, which tend to pull in extra fluid because of their rotation, resulting in a jet that’s effectively larger than an equivalent steady jet. But pulses may also take more energy to produce. … > > … the group found that pulsed propulsion was almost always 20–40% more efficient than the baseline steady jet. At low pulse rates, though, the energy saved through increased efficiency didn’t make up for the extra energy required to spin the ring to make the pulsed jet. But at high pulse rates, the group saw an overall energy saving. > > So jellyfish, and maybe also fish or biomimetic submarines with flapping fins, may in fact swim better than subs, but only if they’re clever about how they produce their pulses. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [May 8, 2012, 12:47pm UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/16 "2012-05-08T12:47:57Z")
> [@t-bonham@scc.net](#): > > This was true for airplanes, too, until jet engines were developed. Could a marine jet be designed the same way, to be more efficient? The Russians have a [supercavitating rocket torpedo](http://en.wikipedia.org/wiki/VA-111_Shkval) - it goes fast enough that the cavitation bubble from the (specially designed) nosecone extends over the whole torpedo (with some small control vanes extending out into the water for steering). There is minimal surface friction, so it more efficient, but it has to go 200+ knots to do it. Si ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 8, 2012, 1:53pm UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/17 "2012-05-08T13:53:52Z")
> [@t-bonham@scc.net](#): > > This was true for airplanes, too, until jet engines were developed. Jet engines are generally less efficient than recip engines with props. Indeed, attempts to make jet engines more efficient often entail high bypass ratios (basically, the jet engine incorporates blades that move air, like propellors). In many cases the blades are inside a cowling; in some, they are [unducted](http://en.wikipedia.org/wiki/File:Nasa_ge_udf.jpg). ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [May 8, 2012, 2:09pm UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/18 "2012-05-08T14:09:30Z")
> [@Whack-a-Mole](#): > > Mind you this is due to high tech design of propellers. I have a recollection of (I think Toshiba) getting into deep doo-doo in the 80’s because they sold hi-tech milling equipment to the Soviets which would allow them to manufacture silent propellers. A thumbnail description from Wikipedia: > [@](#): > > In 1987, Tocibai Machine, a subsidiary of Toshiba, was accused of illegally selling CNC milling machines used to produce very quiet submarine propellers to the Soviet Union in violation of the CoCom agreement, an international embargo on certain countries to COMECON countries. The Toshiba-Kongsberg scandal involved a subsidiary of Toshiba and the Norwegian company Kongsberg Vaapenfabrikk. The incident strained relations between the United States and Japan, and resulted in the arrest and prosecution of two senior executives, as well as the imposition of sanctions on the company by both countries.[5] The US had always relied on the fact that the Soviets had noisy boats, so technology that would make the USSR’s submarines harder to detect created a significant threat to America’s security. Senator John Heinz of Pennsylvania said “What Toshiba and Kongsberg did was ransom the security of the United States for $517 million.” ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [May 8, 2012, 3:10pm UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/19 "2012-05-08T15:10:06Z")
There’s a lot more difference between a fish and a submarine than flukes and propellors. And efficiency has different definitions. Fish (and fish like mammals) are more maneuverable than submarines, and power themselves by consuming other fish and plants in the sea. They have flexible bodies made out of stuff like meat and bones, not rigid metal. The effectiveness of their propulsion is based on their entire body shape, not just the shape of their flukes and fins. Some studies indicate their skin contributes to laminar flow reducing drag. OTOH submarines have torpedos, which even way cool fish don’t have. ETA: Also fish don’t implode if they spring a leak. Though they kind of explode if they’re rapidly depressurized. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [May 8, 2012, 3:54pm UTC](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111/20 "2012-05-08T15:54:16Z")
Jet-type propulsion in boats: Jets have been used to jet water to power boats and Waverunners, but be wary of the results, because jet boats will show worse fuel economy and top speeds, because the props on boats intended to plane also create lift, resulting in less wetted hull (less resistance). Jet boats don’t get this lift, so to do an apples to apples test, you need to power some non-planing hulls (displacement hulls) with jets and compare to displacement hulls with props. . [Next page](https://boards.straightdope.com/t/submarines-vs-whales-vs-fish-are-propellors-more-efficient-than-flukes-or-tails/621111.md?page=2)