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Hot hulls might mean slipperier ships


June 3, 2011

A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water

A scientist has proposed that ships could move through the ocean with less friction, if their hulls were heated to above the boiling point of water

Want to make a ship move faster through the water? Well, one thing that you can do is paint its hull with low-friction or anti-biofouling paint, to keep barnacles and other marine organisms from growing on it. According to Prof. Derek Chan, from the University of Melbourne's Department of Mathematics and Statistics, another approach that should work is to heat that hull up to a temperature of over 100C (212F). His proposed method is based on a 255 year-old principle known as the Leidenfrost effect.

Named for its discoverer, German doctor Johann Gottlob Leidenfrost, the Leidenfrost effect is the phenomenon wherein a liquid, when exposed to a solid that is significantly above that liquid's boiling point, forms an insulating vapor layer between itself and that solid. This is the reason that water droplets dance across a sufficiently-hot skillet, instead of just evaporating on the spot.

Applying that principle to a ship, Chan believes that a hull kept at an outer temperature significantly above the boiling point of water, should cause a low-friction vapor layer to form between that hull and the water. He tested the theory by analyzing high-speed footage of polished balls being dropped through liquid - their drag was reportedly greatly reduced when they were heated to the point at which the Leidenfrost effect occurred.

Not only could this be used to reduce transportation costs and greenhouse emissions from shipping, he suggests, but it could also be used to speed the flow rate of liquid through pipes.

Chan does, however, admit that keeping the hull so hot could increase the rate of corrosion, and is further researching that possibility. There is also the question of whether the energy required to heat the hull (and keep it hot, as it's exposed to cold ocean water) would be significantly less than the amount of energy that would be saved through the reduction of friction.

The University of Melbourne worked with Saudi Arabia's King Abdulla University on the research, which was recently published in the journal Physical Review Letters.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

ok thats good but do not forget that you need more fuel and more just to heat the hull

Mohamed Zeid

Great idea, fascinating forward-looking technology. And thankfully without a word of eco-Kool-Aid or C02.

Todd Dunning

What about the incredible amount of steam that would presumably envelop the ship when it is at stand still!!


Any hull much bigger than a personal watercraft will need a huge amount of fuel to create that much heat. It\'s not only exposed to cold water, it has to boil that water instantly, and the heat of vaporization of water is enormous. Schemes already being researched using air bubble lubrication would be far less energy intensive.


I\'m struggling to recall a more stupid idea.

Maybe the one idea that was more stupid was to dump particles into the atmosphere to reflect heat and combat global warming - by flying hundreds of planes 24/7 (I heard a professor at Stanford describe it).

Vast amount of energy required to keep a hull above 100deg, especially when it\'s constantly being quenched by the ocean.

Much easier to do something like a hydrofoil.


There is also the question of whether the energy required to heat the hull (and keep it hot, as it\'s exposed to cold ocean water) would be significantly less than the amount of energy that would be saved through the reduction of friction.

This must be the understatement of the year. While academically interesting you really don\'t need to have a clear understanding of the huge thermal capacity of water as well as very high heat conductivity of metal nor and advanced physics degree to quickly conclude that the idea that you could save energy this way is ludicrous.


and 6 months after navies adopt this technology, the first heat seeking torpedoes will be deployed...

Mark Temple

I also think (apart from cooking the sailors) the other major problem would be bouyancy.

Metal doesn\'t float as well in steam as it does in water.

If the hull were able to be kept hot enough to continue vapourising the water around it, I think it would sink straight to the bottom of the ocean.

Kinda like trying to swim in the aerated water at the bottom of a waterfall.


They may be able to pipe the excess heat from the engines up to the bow and heat it that way. Maybe it doesn\'t have to boil to be effective? Say 50% or less is better than nothing. Maybe heated air bubbles would be better than heating the water?

Robert Burke

@Robert Burke

They may be able to pipe the excess heat from the engines up to the bow and heat it that way.

Good idea to harness \"waste\" heat. This wouldn\'t increase the overall energy consumption since it would be utilising heat from fuel which has already been consumed. (Same as using heat from an internal combustion exhaust to run a stirling engine or a thermocouple (eg Peltier device) to generate electricity.)

This could possibly be useful in making a combat craft more stealthy by reducing its atmospheric heat signature. I think the rise in water temperature would be far less than venting to atmosphere, because of water\'s greater latent heat capacity.

But a simpler thought, why not have a couple of Venturi tubes which would take in cold water, use the waste heat to warm it and increase its velocity as it is expelled, thus giving a minute propulsion power boost?

Simpler still, heat up the hull and thus \"cook\" any barnacles to death, and thus you\'ve got a \"self anti-fouling hull\" which doesn\'t rely on chemicals, thereby reducing drag.

(And Barnacle Chowder? ;-) )


Nobody even mentioned that the viscosity of water is lower at higher temperatures but heating the hull above the boiling point of water is totally impractical because of the energy consumption, problems with heat distribution and the fact that the ship would have to be insulated inside to keep from cooking the crew and cargo. Development of better anti-fouling, lower friction nano-particle coatings would be a better project investment. Obviously, the scientists in this article have not spent much time around a real ship nor ever had to clean one.


Won\'t someone please think of the algae? :(

Seriously though this would wreak havoc on sealife.

Michael Zarli

It\'s way past april 1st


A lot of ideas that changed the world seemed crazy until it was proven they worked. Like aeroplanes. But this will most likely never become more than an idea that didn\'t work. Maybe even just a silly idea, but not even close to how silly some of the commentary here are! Like \"it would sink straight to the bottom\" as metal doesn\'t float well in steam. So you mean the forces from the water around the steam would be magically neutralized because there is no physical contact? Or \"Won\'t someone please think of the algae?\" Joking, right? Assuming that the idea had worked, i promise hot hulls would be way better for the algae and other sea-life than the millions of tons of poison now applied to boats to prevent algae growing on them.

As mentioned I strongly doubt this idea has a future, but not everything is against it. Heating a hull would take a huge amount of energy, partly because the water surrounding it would be a very efficient coolant medium, but the moment it was hot enough to create the desired layer of steam, it would not only remove surface friction but also form an insulating layer, as steam has way lower density than water and thus doesn\'t transfer as much energy. So, having achieved the hot hull state, the heating energy would be much lower, but it would still need a LOT of energy.

Another problem is that the resistance met by a hull moving through water isn\'t only surface friction. Depending upon speed, shape and size, various pressure patterns, vortexes and resulting waves are normally more important elements in the total resistance of the hull. The imagined steam layer would not at all influence those elements. Considering a tiny steel ball though, as was the experiment, the steam layer would have a total volume not much smaller than the steel ball. Moving it quickly through water would then shape the steam bubble to a droplet shape, which has way better flow characteristics than a sphere. The main reduction in resistance of the hot steel balls would be due to this apparent shape change. Of course this has no effect with larger objects, unless the heat is extreme and creates enormous amounts of steam, AND the object is completely submerged and at significant speed, so the steam has a low pressure field with no surface \"leak\".

Stein Varjord

Turning the cold water off and the boiling water on gets my sister out of the shower really fast.


What the Prof says IS true. It\'s just that bit about keeping 10\'s of thousands of square meters of ships hull heated to WAY above 100*C, and to compensate for the heat loss of enormous amounts of ocean passing at what? Now 100KMH or 60MPH?

That is the tough bit.

I mean forget about heating a cast iron fry pan to 140*C, and swilling a few drops of water around in it...

Try keeping the heat up to a few billion cast iron fry pans and swilling them around in the ocean.

Big ask.

Mr Stiffy

At the Disney company they have a policy of there being no stupid ideas, because even an idea that won\'t work may lead to other ideas that will. Folks here are asking the right questions, and this may lead to solutions for those problems. Others are already making leaps to things like utilizing waste heat, other forms of speeding propulsion, anti-fouling, etc.

\"and 6 months after navies adopt this technology, the first heat seeking torpedoes will be deployed...\"

Along Disney\'s lines: what if this isn\'t practical for ships, but IS practical for the much shorter running times of... torpedoes? This could be a simple way to attempt to approach the performance of Russia\'s supercavitating Shkval torpedo which essentially creates a bubble of air around itself to travel through the water in excess of 200 knots (described as \"like firing a bullet underwater\" compared to regular torpedoes by one submariner).

Perhaps this also has more applicability to nuclear submarine hulls and/or would only be needed when attempting to evade an incoming torpedo?

See, there\'s lots of potentially fruitful ideas that spring off of Prof. Chan\'s original idea, even if his initial idea doesn\'t prove viable.


I see there\'s a lot of objection to the idea. There\'s nothing to say that the WHOLE hull need to be above boiling point. What\'s to say that just heating the bow may have a positive effect enough to offset the increase in fuel usage? Heating the leading edge of the prop?? Only time, experimentation and thermodynamic models on supercomputers will tell.

Of course it\'s just an idea. I\'m glad he threw it out there... even if it doesn\'t get used in the manner described, it may just be the inspiration for a future engineering solution. This is kind of the point of universities and academia, is it not?

Andrew Rockefeller

My favorite comment was Michael Zarli above who is worried that we\'re not \"thinking about the algae\", and \"wreaking havoc on sea life\".

This is why Global Warming died - in a nutshell. We on the right have been subjected to comedy statements like those above for our entire lives. And when the exact same folks came up with global warming, there was absolutely no way we were going to go for it. Not ever, no how.

I can predict Mr. Zarli\'s opinions on other future technologies, from genetically modified foods to nuclear power as well. All well meaning, and all putting politics before science.

Todd Dunning

I know many reserachers tend to get wrapped up in their work without seeing the bigger picture, but do they all have no common sense at all? There are just so many things wrong with this idea I would be embarrassed to put my name to having come up with it.

Mr T

Who said they had to do this with the ships hull?

Just think how fast a white hot torpedo could travel if it were surrounded by nothing but a thin layer of boiling water.

And if you are in combat with ships and/or other submarines it might just be enough to heat the surface of your torpedoes up just enough so they travel through a low friction layer of steam as they are launch toward your enemy.

You all need to think beyond the end of your nose.


Is the idea to create a scenario that makes the ship perform as if it is traveling through air/steam? Why don\'t we just reconsider the airplane for such a task?


It\'s possible to simulate the Leidenfrost Effect without heat through the use of Extremely High Frequency (EHF) sound waves generated against the outer shell of the vessel. Net result is safer, easily on/off, far less energy consumed.

Outside Looking In

jjgg38 - June 6, 2011 @ 06:31 pm PDT

If AGW was real there would not be the secrecy, and fraud at the core. Nor would there be the extortion to keep research with differing results out of the peer reviewed journals. And the ten year predictions that they made ten years ago would have come true.


It astonishes me that complete ignorance of physics and the apparent inability to actually read the article in no way inhibits the offering of indignant opinions!


I agree with quax, even if (and it is a really big IF) you could make it more efficient than just adding more hp to the propulsion, it would be pointless for military applications. I know that probably wasn\'t this researchers primary goal, but ships have a hard enough time masking their IR signature now, hate to complicate the problem. Thermal masking would become a bigger chore than RCS-ing a ship.

Tyler Totten

Why aren,t fish hot to touch? No free lunch


The basic idea is to use vapor or gas to provide lubrication between the hull and the water. The hull itself coud be redesigned in layers with the outermost layer in contact with the ocean separated with insulation from the inner and thicker hull. The outside layer might incorporate small holes to permit the passage of compressed air, hot air or steam. Since the layer would be thin, it would not require vast amounts of energy.

Adrian Akau

@gizmag... your comment posting scripts suck, I\'m writing this for the second time, than you very much @outside thinking in, I think that would certainly harm sea life @everyone else ... stop hating so much, if you\'re all that smart why don\'t you come up with a better idea

From principle this is a great idea, now from practicality, it just might not work. Or it will work but it might turn out to be more fuel inefficient as just having a normal cool hull. Now here\'s what I thought about, generally ships engines generate a lot of extra heat that just gets dissipated into the atmosphere, obviously having cooler and more thermodynamical engine is what everyone has been working on for the past decades, BUT what if we would develop smaller engines, working at much higher rpms that would heat up a lot more then what we have today, then we could use the hull as a coolant for them, thus enabling us to use both the heat and the engine output more efficiently. If this effect would for example make ships run twice as faster on engines half or less the size of the others then it would surely be an improvement in fuel efficiency not to mention in cargo hold space (because of less space needed for the engines and less fuel needed for trips).

This was my take on the idea, and I\'m sure that Dr. Chan also took these factors into consideration before publishing this idea. So just stop hating on other people, that is easy, coming up with ideas and being constructive is hard.

Stefan Padureanu

apart from the bubbles, a neoprene type \'paint\' could dampen viscous turbulence layer from gaining beyond a certain thickness/distance from hull\'s surface. The inspiration taken from dolphins skin\'s, they presumably swim 20 % faster than would be mathematically be expected,.


modena, emilia, romagna, italy, ea.eu.

Søren Algreen-ussing

It is well known that it takes a large amount of energy to boil a given amount of water, compared to just raising the temperature of the same amount of water for instance. Also well known from experience is that the rate of mineral accumulation on the hull surfaces would increase tremendously, decreasing the rate of transfer of heat through the hull and thus requiring even more heat energy to maintain the boiling.

Facebook User

As many have already alluded, from a thermodynamic standpoint, this is undoubtedly the silliest posting I\'ve ever read at Gizmag. Why even post it? Wormholes are more probable than this. Supercavitating torpedos already exist. I would think that technology applied to shipping would have a greater chance. If not that, the tried and true hydroplane. Just because somebody has a daydream, that should not constitute a litmus test for publication. Geesh!


How can someone trained in the sciences be so removed from reality? Silliest EVER.


What about the small surfaces used by hydrofoils? Would it work for that application?

Tony Medlin

How about less buoyancy though. When the water approaches the boiling point, you will get air vapor and thus no medium for which the ship is to float. Hence why the great doctor saw a less drag coefficient with the marbles. they likely sank. If we utilize Nature and find a way to harness the great potential of the hungry fish who regularly clean sharks teeth, I believe it would work to a better advantage. Rather than fight nature believe in it! God had it first!

The Tech Bandit

There might be some advantage to heating the leading edges and high drag points of a ships hull. The energy cost might work out. Heating the propellers would be counter productive you don\'t want the prop to cavitate, you need the prop to push against the water not an air /vapor pocket. The idea of a very hot Torpedo full of explosives concerns me especially if you plan to warm it prior to launch. Heat and Torpedoes don\'t mix so well.

David Cole

I agree that this is perhaps the silliest idea ever, but it did generate some lively discussion, and I agree that sometimes a silly idea can lead to real possibilities. However, the most utterly and completely foolish utterances in this series came from Todd Dunning.

\" This is why Global Warming died - in a nutshell. We on the right have been subjected to comedy statements like those above for our entire lives. And when the exact same folks came up with global warming, there was absolutely no way we were going to go for it. Not ever, no how.\"

Todd, please take the trouble to read the book \"Storms of My Grandchildren\" by Dr James E Hansen. He has been an eminent climate scientist for NASA for many years, and reading his book will give you the facts to understand the problems of Climate Change that you totally lack at this point.

You have mistaken opinions for facts, and substituted right wing arrogance for understanding. Quite seriously, read the book. You will be astonished at how much is known, and how much is being ignored by so many. I feel confident that you would not willfully subject your children and grandchildren to a disastrous and dangerous future, but if you do not correct your lack of information, you will do just that, and not just to your children and grandchildren, but to the entire world.

Global Warming has not died. If only it had. Instead it is inexorably coming toward us like an extremely large and slow global tsunami. To check this fact, refer to the recent articles about the increased melting of permafrost and the accelerating melting of the Greenland Ice Mass. Parts of the coastline of Alaska and other regions in the Arctic are literally falling into the ocean because the sea ice is disappearing and the formerly frozen ground is melting. We all need to wake up and face the facts, because to fail to do so will be hugely dangerous.


jjgg38, The ground does not melt, it thaws out. Any ice crystals melt out of it and evaporate and it\'s cyclic in nature. We have been having global warming and cooling cycles for millions of years. It\'s just a recent development that man thinks he is important enough to affect change either direction! I\'ve got two snipes I have been keeping all these years just for this moment. I got em way back when hunting was still allowed! Remember snipe hunting? Boy, those were the good ole days. I\'ll sell them to ya cheap! 8-)

Will, the tink

@jigg38 Go read the e-mails from the CRU. You can read the AGW fraud in James E. Hansesn\'s own words, along with the rest of the \"Hockey Team\". One especially damning file is the 15,000 line HARRY_READ_ME.TXT file. That\'s a journal of programmer\'s notes about everything he had to do to make their HADCRUT 3 program spit out the fraudulent hockey stick shaped plots.

When terms like \"false WMO codes\" (for temperature monitoring stations that never existed) \"fudge factor\" and \"apply artificial correction\" and \"apply very artificial correction\" turn up in program source code and programmer\'s notes - it\'s not at all science, it is FRAUD.

The \"science\" of anthropogenic global warming has been proven to be a fabrication of Dr. Hansen and his buddies - proven by their own words and deeds they never expected a whistle blower on the inside to let out.

Gregg Eshelman

Wow. Worms crawl out here... This article isn\'t about global warming, and I strongly doubt I\'ll be able to convince an ignorant of his ignorance, but I guess I should try... Proper scientist in this field do disagree on a lot of topics, but ALL OF THEM AGREE on some basics: 1. Global warming is real and a serious threat to the stable climate conditions the Earth had for about 10 000 years. 2. Human activity has at least increased the problem significantly. 3. Changes significant enough to be irrevocable and not accidental have been measured, making it not theory but facts.

The changes have been compared extensively with data from millennia of history, and the change that has already happened now is totally beyond anything that has ever happened when considering the speed of the change and the number of species becoming extinct. When the dinosaurs \"died out\", (they actually didn\'t, as birds are dinos) it happened way slower and with way fewer species.

Believing that vigorous denial or voting Bush or so will fix this, is even more stupid than it seems. I have no respect for stupidity coupled with intolerance/aggression. It\'s capable of making me intolerant. That\'s all I\'ll say on this. Now buzz off! Stick to the topic! Hot hulls, not hot sculls.

Stein Varjord

\'Slipperier\'? Is that even a word?

Rahmat Shazi

Not going to happen... Because you would have to heat the hull even hotter than 212deg... Good luck heating the hull. Take a skillet what happens when you keep pouring cold water on it????

Alvaro Perez

Probably one of the silliest ideas posted on Gizmag (second only to the robotic sweaty armpit; and before you ask, yes, it exists!!) Lots of good ideas in the comments section: hydrofoils, airplanes(I prefer zepplins) or let\'s not forget wind power: the humble sail! Why people waste any energy traversing the ocean when there are sails, is beyond me... Most of the things you\'d want to ship over an ocean can survive the time it takes to get there under sail-power. Food which has an expiry date should whenever possible be grown locally, and not shipped to begin with!!

Jeremy Nasmith

If the energy-loss to heat from surface drag was greater than the energy requirement for heating the hull to Leidenfrost effect inducing temperatures, wouldn\'t the friction itself heat the hull to these temperatures, thus eliminating the need for additional heating?

Silly unworkable idea, and silly commenters for taking it seriously.


This idea is not a dumb one although it quite likely will not work. The mistake most people are making is that the hull is not being continuously cooled by the sea. Well, it is, but the heat transfer from metal hull to sea would be orders of magnitude higher than the heat transferred through a layer of steam. Probably the biggest challenge would be reaching the Leidenfrost point initially while the hull is still in direct contact with liquid water. Also retaining the steam layer. If it had to be continually boiled out of the ocean, then yes this would consume many times more energy than a traditional hull.

@Newsjunkie - No. The energy lost to heat from surface friction would rapidly be transferred to the sea water preventing temperatures required to reach Leidenfrost. Once you pass that point the heat requirement will drop hugely.

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