already been patented
What? China want the rest of the world to respect THEIR patents....
Ignoring the propaganda and "capability inflation", how about the rest of us ignore these patents.....
The Ministry of National Defense of the People's Republic of China this week reported the first successful test of a magnetohydrodynamic drive that could let ships and submarines sneak around almost totally silently. The system, built by the imaginatively named state-owned China Shipbuilding Industry Corporation, was …
Silent propulsion isn't that hard - regular low speed props with modern CFD design and precise CNC machining are very quiet.
Harder is getting silent high power engines to drive them. The MHD drives used so much power you need a nuke, which is far from silent. The Swedish boats used a liquid oxygen + diesel Stirling cycle engine - one moving cylinder but very slowly and smoothly.
"Harder is getting silent high power engines to drive them. The MHD drives used so much power you need a nuke, which is far from silent."
RIght, for higher power levels, nuclear reactors make quite a bit of noise. Higher power means you need more coolant flow. At low power you can get away with slower/fewer pumps [or in the case of SOME submarines, no pumps at all]. Given that the magnetic drive needs a SHIPload [ha ha ha] of power, you'd run lots of or faster speed pumps, meaning noisy power plant.
So yeah. This is probably why U.S. subs use "a different kind" of propulsion.
/me recalls a rumor from back in the 1980's, that the Trident missile boats were SO quiet, you could only find them if you were lucky enough to find "a sound hole in the water' the size of a Trident submarine.
[and I expect that technology has improved considerably since then]
I also remember a story from a few years back where the USA where have a massive sea battle simulation / training exercise in the middle of the Pacific and right in front of the US command carrier a Chinese Submarine surfaces, opens their hatch waves at the carrier and subsequently submerges without a trace.
It really upset the naval manoeuvres especially since they couldn't track the boat with the multitude of tracking ships / submarines at hand.
I work in the submarine industry and hear all the nuggets of cat and dog 'cold war' antics, which most of them are VERY amusing, with lots of captains just plain showing off.
The new Australian subs are rumoured to be even quieter than the swedes and have underwater endurance ratings that rival nuke boats (which kick out a shitload of heat thanks to the nuke and may be possible to detect because of that, if someone doesn't develop a mobile neutrino detector in the meantime)
> The new Australian subs are rumoured to be even quieter than the swedes
Do you mean the ones that are still pretty much on the drawing board, where doubts have been publicly raised/leaked to press about the feasibility of the refit (the one it's based on is a nuke and in spite of Australia being incredibly well endowed with uranium, we seem incapable of countenancing anything more radioactive than a banana). Getting nailed together in south Australia because there's a bunch of seats that will swing to NXT if they dare buy something off the shelf (not saying that they should be built elsewhere, but it shouldn't be to prop up a local candidate because your party is on the nose). Oh and apparently can't keep our military secrets secret either.
The ship used liquid helium-cooled superconductors to get up to speeds of 15KPH (9MPH) and later prototypes couldn't beat that speed.
A prototype is a prototype is a prototype. Something later than a prototype is no longer a prototype. A "later" prototype is a development.
According to wikipedia, there are various types of err prototypes
Paper Prototype, Proof-of-Principle Prototype, Form Study Prototype, Visual Prototype, User Experience Prototype, Functional Prototype, Working Prototype
Lets hope the sub isn't a paper prototype, it might get a bit soggy.
"But there can be only one prototype"
No, because there is nothing in the definition that specifies that there can only be one "proto", unless you can prove otherwise. A prototype simply means it's a pre-production unit. If you want to get more technical, if you make another one, the previous one may no longer be considered a prototype and is instead a reject.
Does this prove otherwise?
original or primitive.
first or earliest.
So it means original, first or earliest. Now if you think you can have more than one first-type, or more than one original-type, or more than one earliest-type, your understanding of English is wrong.
Your understanding of reality is wrong. Two different ways.
Firstly, I can make a prototype. And then, if I need to, I can make an exact duplicate. Why would I need to? I might damage the first one. Or I might wish to speed up testing and development by allowing more than one team to have a prototype to investigate. Since they're identical, and even you agree that one of them is a prototype, by all the laws of logic and English the second must also be a prototype.
Secondly, I can make a prototype. And then I can make something which is similar to that prototype but which differs in significant ways. Call them A and B. "A" may have been a prototype for "B." But "B" may be a prototype for "C." And perhaps further down the alphabet until we get to a pre-production model (which can still be regarded as a prototype): we've proved the concept, now we're trying to optimize how we make it. Until finally we get to a production model. Production items are not prototypes, but that which precedes the production item is a prototype.
" 1. a combining form meaning “first,” “foremost,” “earliest form of,” used in the formation of compound words (protomartyr; protolithic; protoplasm), specialized in chemical terminology to denote the first of a series of compounds, or the one containing the minimum amount of an element."
You forget. "First", "foremost", and "earliest" can be applied to a collective, so there can be more than one prototype as they can be referred as a group. The importance of the singular in the word really only applies in chemistry where it refers to the first step in things like a reaction chain.
Then I suppose a 'protocol' must be a first 'col', whatever that is. And there can be only one protozoan, all the other amoebas, paramecia, stentors etc. must be that protozoan's descendants. And only one thing can be prototypical, all the others are imposters.
I could go on, but I think you get the idea. You're arguing from the etymology: in Greek, protos (προτος) means 'first', but that doesn't mean it always (or even ever) means that in English.
There can be a series of prototypes testing various configurations and designs for a project like this. The key is the power consumption requires a power source. It sounds like a trade off between an extremely quiet engine with a noisier power source. This ignores other sources of noise like propeller cavitation which can be significant at speed. Also, one has to generate the electrical power on the sub which implies a reactor with a turbine driving a generator. This the area that makes nuke boats noisy not the propeller (at low speeds at least)
The rule for subs has been to be stealthy one must be moving relatively slowly as higher speeds mean more noise is generated from something.
KINAWA – The Japanese Navy today announced a comprehensive plan to retroactively rename its vessels, including famous ships from history, to avoid confusing them with the popular online game Kantai Collection.
“This is all quite frustrating,” said Admiral Yamada, who is spearheading the renaming effort, during a press conference at the Okinawa Naval Headquarters. “It’s bad enough that most people think the Yamato is a space ship. ...
El Reg, you're linking to an article stating that the sub uses a permanent magnet motor. That's a very ordinary motor, though they're usually not submarine sized because big magnets are insanely dangerous. It says nothing about magnetohydrodynamic drive.
Magnetohydrodynamic drive needs to use AC unless you want giant foaming and corroding electrode contrails behind your sub. That AC would make more noise and EM than a permanent magnet motor.
"Wouldn't magnetic anomaly detectors have a rather easy time spotting this sort of thing, or is there a submarine-friendly way to shield giant magnetic fields? Lots of mu metal?"
MAD systems aren't as popular as they once were. The old P-3 Orion had a MAD, but the newer P-8 Poseidon (UK is buying these) does not. MAD requires a low pass over the water as well. It is not clear how effective MAD really is or was. I might have to brought back if magnetic drive becomes popular.
Let's see. With just one tube, the field lines from the magnet poles should be fully contained within the water channel, with soft iron cores used to form the poles themselves and conduct the field either side (the iron in a transformer or a motor "conducts" the magnetic field, and is used to close the magnetic circuit). Without that the field just splays outwards like the classical magnetic field pattern, and that's a big inefficiency.
However, I've an inkling that iron cores and superconductors don't mix; something to do with high strength magnetic fields (i.e. concentrated by an iron core) quenching the superconductor. So if there is no iron core shaping the field around the water duct, then the field will go everywhere, and it will show up more.
Basically, I don't know for sure. I've actually seen the Japanese drive unit that's on display in Japan. As you can see there's 6 thrust tubes in the unit arranged in a circle. I strongly suspect that the magentic field is also circular, with field coils in between the tubes. The field is probably quite well concentrated in the tubes, so any leakage is probably quite small.
The unit itself is quite large; it's about 5'6" across. Certainly a propeller of the same diameter would have moved a much larger ship much faster than the Yamato for the power it had. I couldn't see any reason to think that the unit was anything other than "as good as was physically achievable". I'm fairly sure that the physics of passing a large current through salt water in the presence of a large magnetic field to form a propulsive jet is too limiting to be useful.
From the article:
Because no moving parts are involved, the system is pretty much silent running but for the sound of water. As a result, it could be perfect for stealthy submarines or naval ships doing secretive work.
As others have already pointed out, the total noise emission of a vessel comprises machinery noise and propulsive noise. With MHD being so massively inefficient, you need a lot of machinery with attendent noise generation. The Yamato 1 was essentially all engine (so lots of machinery noise), and it could barely move.
For a submarine it's far better to have a small nuke on tickover (I think the modern ones can rely on convection at low power settings, so eliminating the machinery noise caused by the coolant pump) gently driving a well designed propulsor (a shrouded fan; propellers aren't as good). That will drive the submarine at quite low speed whilst making hardly any noise.
There's little point going fast; the water flow noise ruins your own sonar, so you can't hear anything, so you've no idea where anything else is or whether they're attacking you. Submariners don't like not being able to hear...
You're right about flow noise ruining your own sonar; however, high speed is very important tactically and strategically, as it allows you to rapidly change the location of your sub.
Tactically this is important to e.g. outrun a torpedo or quickly get a 2nd bearing on a contact in order to estimate its distance. That's why a common submarine tactic is "sprint and drift". It also allows you to move ahead of your target and stealthily sit and wait on its predicted path.
Strategically, sustained speed allows you to quickly reposition your subs within or among theaters, often without your opponents noticing.
"Lots of mu metal?"
Might not be necessary; consider hard drive voice coil magnets. You arrange opposing pairs of magnets so their magnetic fields effectively negate each other (when observed from the outside). That being said, I have found a few laptop drives that will attract magnetic materials; I suspect these to only contain a single magnet (though I have not opened any).
Disclaimer: not an expert on magnetism, or any other aspect of physics; this post could be completely untrue.
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