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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.
I thought putting millions of bubbles around a ship was a good way to hide it from SONAR?
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.)
'Sensible' is a curse word.
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
Better known as 318230.
The Russians already use it, but mostly for speed. It isn't all that usefull for stealth. (As already mentioned.)
So it's not useful for submarines, but for many surface ships it is very useful. And for torpedos it is killer. IIRC, they have a couple of rocket-powered supersonic torpedos that panicked the US Navy when first demonstrated...
'Sensible' is a curse word.
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.
Learn to love Alaska
Believe you are taking about the Prairie-Masker system http://en.wikipedia.org/wiki/Prairie-Masker
Putting bubbles around a ship will decrease its displacement, thus making it sink more to compensate for the loss of displacement, it will sink until it displaces exactly the same weight in water as the ships weight.
A thin layer of bubbles will not do that. They will be at the pressure of the surrounding water and provide the necessary force to support the ship. To sink lower, the ship would have to move them aside - which it is already doing - but are limited in their ability to move by the resistance of the surrounding water. Meanwhile they are continuously replaced from the air source.
Now if you have a DEEP foam of bubbles beneath and around the ship - allowing the air to move sideways rapidly - the ship would indeed drop as if it were in midair - or (if the foam is only partly air) attempting to "float" on something less dense than itself. But a layer of bubbles against the hull will not do that.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
Democracy is a sheep and two wolves deciding what to have for lunch. Freedom is a well armed sheep contesting the issue
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.
SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
Well it is basicly forced Cavitation of the hull and while there is no reason why this wouldn't work there are a few issues why you might not want to do it.
first the noise - normal ships going throught water don't make that much noise - but a cavitation prop does.. this is bad for sea life..
the second issue would be that a cavitating prop doesn't propel very well.. infact a prop running in backwash doesn't work well. How are they going to keep the air from effecting the props efficence - if you pump that much air into the water then the prop isn't going to be as effctive.. unless you position it below the cavitation but then you are increasing the ships draft.
thrid would be Bouyency - pumping the air into the watter will chance it's density - making the ship sit deeper - again increasing it's draft..
when you increase a ships draft it increases the amount of energy to move as you have to displace that much more water. - i like the idea with sails better my self..
'...if only "Jumping to a Conclusion" was an event in the Olympics.'
I wish I had mod points. Hmmm - haven't had any for months. But you are spot on. The trials with putting modern sale systems on large container ships look most promising.
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http://www.newscientisttech.com/article/mg1852488
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.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Or kites?
About Cavitation Torpedoes:e nt_applications
http://en.wikipedia.org/wiki/Supercavitation#Curr
On a sidenote:
Vikings already used bubbles to lessen the drag. They constructed the wooden boards on a ship's bottom on a special way, basicly overlapping them downwards and thus trapping air in the pockets to create a vortex and ultimately decrease friction with the water.
To my shock i can't find any solid online references to vikings using this approach.
I've seen it on TV (i guess Discovery) once.
Hivemind harvest in progress..
What's the point of worrying about it? The ships will never be built to use this technology. I honestly cannot remember a single prediction made on slashdot of promising new technologies, which actually came to fruition. They always have "just a few hurdles left" before they transformed our lives. In this case, it is literallly and figuratively vaporware.
Ok, I just found a use for the quote tags- there's a new button beside submit. Actually, this technology is already pretty well understood and proven- it just hasn't been applied to a hull the size they're talking about yet. It's usually used in warfare either for defeating sonar (the bubbles mask the sound of submarines) or for speeding up torpedos (the Russians have used it for years to make their torpedos more accurate).
SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
You might be looking for this.
Free beer is never free as in speech. Free speech is always free as in beer.
FTFA linked by grandparent:
Gas. Not vacuum. The first thing I thought when I heard about the Shkval is "I wonder if the technology could be useful at ship-sized scales?", the first thing I thought when I saw the article here on slashdot was "Woo, supercavitating!"
j'ai découvert une démonstration vraiment admirable (de ce théorème général) que cette si
I remember a book about the Bermuda triangle that pointed out that the number of ships lost in the triangle was proportionate to the amount of shipping in that area. There is no mystery.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
You've just described a hovercraft or surface effect ship. Contrary to the grandparent post, wave drag for a ship does not increase as the square of speed. It increases as a complex function of the ship's dimensions vs. speed. It initially loops up sharply with increasing speed, but then dips asymptotically to zero. The initial mathematical research characterizing wave drag for this type of ship was done by L. J. Doctors at the University of Michigan in 1970 for his Ph.D thesis.
Hovercraft and SESes as well as smaller watercraft which can get "on plane" take advantage of this - once you get over the initial hump, you are traveling fast enough that the water doesn't have time to react to the pressure of the ship on top of it. The water doesn't have time to try to "get out of the way" thereby creating waves which sap away energy. The water behaves almost as a solid, generating very little wave drag. At these high speeds, most of your drag comes from skin friction and air resistance.
I should note that TFA refers to methods of making the bubbles "stick" to the hull, rather than using overpressure to release a steady stream of bubbles (air lubrication) or contain a single large bubble (hovercraft or SES).