Future Ships Could Float On Bubbles

MattSparkes writes, "Creating a layer of bubbles underneath a ship's hull could improve fuel efficiency by 20%. When you consider that 90% of the world's goods are transported by sea, the importance of this discovery is obvious. 'Conjured up from thin air at the flick of a switch, this slippery blanket will help transport a fully laden tanker or container ship across the ocean at higher speed, and using far less fuel, than ever before... There is currently no other technique in naval architecture that can promise such savings.'" The article looks in some detail at the engineering problems that will need to be overcome before this technique is practical.

Comments

other options

[User 956]

Creating a layer of bubbles underneath a ship's hull could improve fuel efficiency by 20%

But have they tried rainbows and/or fairie dust?

Re:other options

[Marxist Hacker 42]

The difference is in the thickness of the air and the direction.

Large Bubbles from the sea floor of a lighter-than-air variety=very bad.

Small bubbles surrounding a torpedo= Good for the Russian Navy (look up supercaviated torpedos, which basically encase the torpedo in a bubble to speed it up).

Microbubbles that allow some of the hull to stay in contact with the water=good for fuel usage.

Re:other options

[Jah-Wren Ryel]

Whether you're a sailer or whether you're a freighter,
You're stayin afloat, stayin afloat.
Feel the bubbles breakin and everybody shakin,
And were stayin' afloat, stayin' afloat.
Ah, ha, ha, ha, stayin' afloat, stayin' afloat.
Ah, ha, ha, ha, stayin' afloat.

Well now, I get low and I get high,
And if I can't get either, I'm still dry .
Got the winds of heaven on my shoes.
I'm a bubblin' man and I just can't lose.
You know it's all right. It's ok.
I'll sail to see another day.
We can try to understand
The disco science effect on man.

Boat's goin nowhere. somebody help me.
Somebody help me, yeah.
Boat's goin nowhere. somebody help me.
Somebody help me, yeah. stayin afloat.

Well, you can tell by the way I use my walk,
I'm a sailin' man: no time to talk.
Bubbles loud and waves are warm,
I've been tossed around since I was born.
And now it's all right. It's ok.
And you may look the other way.
We can try to understand
The disco science effect on man.

But how will it affect buoyancy?

[with_him]

Since methane hydrates releases are still suspected in the sinking of ships, how do the researchers account for the loss of buoyancy? Since this research calls for redesign of current ship building know-how, how are they planning on addressing the buoyancy part of the equation? To read more check out this http://www.newscientist.com/article.ns?id=dn1350 and http://jbj.wordherders.net/archives/000992.html someone trying to weaponize the buoyancy concept. http://www.nexusresearchgroup.com/fun_science/buoy ant1.htm A fun science experiment for the kiddies, or others that want to understand it better.

no other technique???

[DerekTomes]

"...There is currently no other technique in naval architecture that can promise such savings..."

Except sails.

Re:no other technique???

[AK Marc]

They go great together. When you have the wind, you raise the sails and turn the engines down. When you don't have the wind, you take the sails down. You have the same speed either way and are never off schedule. The difference is that you get there using less fuel when you use the sails in addition to the engines.

Re:no other technique???

[dubbreak]

..sale systems..

Wow, just got a great idea: They could put Walmarts on large container ships and use the everyday low prices to offset the high price of fuel.

Re:Have they factored in....

[Daniel_Staal]

Have they factored in the amount of energy required to create the layer of bubbles? Seems like creating a layer of bubbles around the hull of a giant ship would take quite a bit of energy.They are moderately intellegent people. They do think of these obvious things...

(For reference: It is a major problem for one of the approaches being researched, but only one. Another approach already has a 40% reduction in friction by diverting 3% of the ship's power. Well worth the expendeture.)

Bzzzt

[Dan East]

When you consider that 90% of the world's goods are transported by sea

Bzzzt. The submitter misstated the article, so this statement is flat out wrong.

From the article (emphasis mine):
in 2003 more than 90 per cent of all goods that were sent around the globe went by ship

So in the context of global shipping, 90% of goods are transported by sea. Obviously far, far less than 90% of the world's goods are transported globally in the first place.

Dan East

In case anyone is interested

[noewun]

In what

The idea of air cavities has much in common with supercavitation, in which a submerged object such as a torpedo creates a single large bubble around itself. This slashes skin friction, bringing remarkable speeds within reach (New Scientist, 22 July 2000, p 26). Perhaps not surprisingly, Russian engineers who first developed supercavitating torpedoes have not only done plenty of research on air-cavity lubrication for ships, but have also put their ideas to work.

refers to: Shkval. Scared the bejesus out of the U.S. Navy.

Re:In case anyone is interested

[phayes]

refers to: Shkval [fas.org]. Scared the bejesus out of the U.S. Navy

Uh, no. To see underwater you use sonar, but the shkval's propulsion is so noisy that it is essentially blind once launched. It's major utility was as a nuclear tipped revenge weapon. Don't forget that when the shkval was being developped, russian subs were relatively deaf & noisy compared to the US & the UK. In that scenario, when a Russian sub discovered that it was being targeted by an unavoidable torpedo, launched from a sub they hadn't detected, they would launch a few shkvals back up the vector that the torp was detected on. Hopefully one of them would take out the opposing sub or at least cut the wires that are used to direct the torp from the sub. An autonomous torp is easier to shake than one that has a subs sonar directing it so cutting the wires gives the russian sub a better chance. Once Nato was aware of the shkval, attack doctrine was changed to include a quiet swim out & dogleg so that the shkval would be targeting the empty sea & not the Nato sub.

Using a shkval also means nuclear first use, which both sides wanted to avoid.

This works best at slow speeds

[nels_tomlinson]

I haven't yet read the fine article. I do know just a bit about naval architecture. This should help with skin friction, which is the big deal at low speeds. For higher speeds, the resistance which comes from making the wake is the big deal, since the wave-making resistance increases roughly as the square of the speed.

So, what's ``low speed?'' That's probably going to be any speed much below sqrt(waterline length in feet), with units of knots. So, for a 400-foot long ship, anything less than 20 knots is in the speed range where this is likely to matter. For a 900 footer, anything less than 30 knots. Most ships travel in that low speed range, so this could be practical.

Re:Don't some military ships use this?

[drinkypoo]

Uh, creating bubbles by cavitation is entirely different, happens for an entirely different reason, and has nothing whatsoever to do with this. YOU WIN TEH PRIZE!

Barking up the wrong tree

[Control Group]

What they ought to do is replace the oceans with frictionless liquid helium. That would be way more effective.

Yes and it has been in use for a while

[LWATCDR]

http://www.fas.org/man/dod-101/navy/docs/swos/stu2 /NEWIS9_7.html
Some people will confuse the idea of bubbles with cavitation. Cavitation is loud and is avoided but it is caused when a screw manages to cause a phase change. The water turns to vapor and the the bubble collapses making a lot of sound and can even erode the metal on the screw.
The bubble of air that the navy uses don't collapse so no noise instead it acts like an insulator.

I wonder if you could use the exhaust gases of the ship for the bubbles for shipping application? You would have to cool the gas first but it might be a bit if a free lunch.

Bathtub bubbles

[kitzilla]

"Junior! What are those bubbles in the bathtub?"

"Just reducing drag, Ma."

Re:Not really the same.

[PWNT]

The supercavitation bubble negates the need for torpedoes that can steer.

Ships move slower than traditional torpedoes, however the relative difference is not huge, so a ship can attempt to evade the torpedo.

These new torpedoes travel so fast, that any amount of evasion is useless! IIRC the new torps are travelling at 200 knots, like 400 km/hr or something. This is a huge difference compared to older slow torpedoes travelling at 50 knots.

These very fast torpedoes would be used to sink the larger fleet carriers from submarines. Get under or anywhere near the carrier, shoot 3 at the carrier and go on a silent run to creep away.

Actually it floats HIGHER

[Ungrounded Lightning]

What they are talking about here us just surrounding the hull with a thin layer of bubbles.....maybe the ship sits a couple inches (to pull a guess out of my rear) lower in the water....but there's not going to be any danger of sinking a ship...

Actually it floats HIGHER - by about the thickness of the air film. (It would float higher by EXACTLY the thickness of the air film except that the film is compressed slightly by the higher water pressure at the bottom of the boat.)

To understand it:
  - The film displaces water, just like the hull.
  - If the hull sinks marginally, the film stays about the same thickness and it's the water below that is displaced.
  - So the film of air acts like part of the hull.
  - The total amount of water displaced is the amount displaced by the hull PLUS the amount displaced by the air.
  - But the air under the boat is about the same density as the air above the boat. So only the craft's weight (plus any surplus weight of air from its compression by the higher pressure below the hull) is supported by the displaced water.
  - Thus, to displace its own weight the hull plus air system must have the hull higher than the hull-only system by about the thickness of the air barrier.

Re:Not really the same.

[Anonymous Coward]

These new torpedoes travel so fast, that any amount of evasion is useless!

They are so fast you can't "see" them coming on sonar. LIDAR doesn't have very good range under water and RADAR doesn't work at all. If it was fired from enough below the surface that the shock wave doesn't hit the surface before you're hit, you'll never know it was coming.

Flapping Tails

[Garrett Fox]

It's also worth looking at MIT's RoboTuna and RoboPike, robotic fish, and the penguin boat Proteus. These projects demonstrate that fish-like fins or flippers substantially improve propulsion efficiency vs. propellers, because they generate vortices of water that actually push a vehicle forward. MIT sees these vortices as the answer to Gray's paradox, which said that a dolphin would have to be stronger than it is to swim as fast as it does. (That article disagrees.)

A flapping drive would also have the advantage of looking cool.