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Acoustic "Superlens" Could Make Subs Invisible
Al writes "Nicholas Fang and colleagues at the University of Illinois at Urbana-Champaign have created the first acoustic superlens, which could be used to create high-resolution ultrasound images, and perhaps ultimately make subs and ships invisible to sonar. Researchers have previously developed materials that bend light in ways that appear to violate the laws of physics, creating so-called optical superlenses. The acoustic superlens consists of an aluminum array of narrow-necked resonant cavities filed with water — the dimensions of the cavities are tuned to interact with ultrasound waves. When ultrasound waves move through the array, the cavities resonate and the sound is refocused."
Title should be "Acoustic superlens could make subs inaudible".
Thanks to this ground-breaking scientific research, submarines will be even better equipped to collide with each other.
I haven't RTFA, big surprise, but just a thought...
If the cavities have to be tuned to match the sound, then what happens if somebody comes up with a sonar that uses variable pitch?
Or even just two separate sonar systems on a ship/sub/whatever, that use two different frequencies, with no matching harmonics.
If something shows up on one, and not the other, then somebody's trying to hide.
"City hall" in German is "Rathaus" Kinda explains a few things......
When I saw "subs invisible" I thought "Cool, I can get rid of those 2 huge black boxes hooked up to the receiver" but no...
Trolling is a art,
thank you star trek :)
Theorists have been working on materials that bend sound waves backward for several years.
So you mean, if this technology moves forward, and ends up getting incorporated into conventional home/portable audio systems, we may be able to settle once and for all whether or not Paul is dead?
The claim of "invisibility" sounds like exactly what one would write in a grant proposal to the Naval Research Lab.
Never mind it's very very unlikely.
Any practical cloaking device is almost certainly going to work in only one linear direction and at one temperature and frequency.
And imperfectly at best.
And probably be larger than what it's trying to cloak.
But sonar pulses are spread in frequency and can arrive from any direction, making such a cloaking device useless.
This just sounds like the perfect phrase to put in a grant proposal to get some Admiral to sign off on it.
Passive sonar, on the other hand, still works fine.
After all, the thing's got to have a tailpipe.
How can I believe you when you tell me what I don't want to hear?
Oh noes! Teh whales! You're right - the entire western Navy should just pack up and go home. I'm sure our enemies, being the reasonable and thoughtful people they seem to be, will follow suit.
Another day, anther Slashdot cloaking device story.
I think there's room for the GP on Obama's cabinet! Mr. Prez seems to like people who make knee-jerk decisions/comments without thought to their long-term ramifications.
It's the ostrich philosophy - if you can't see it, it can't see you. If all incoming waves (light or sound) are diverted around the object, then it can't "see" anything. If it absorbs some, then it will appear dark against it's background. Granted, it doesn't take much light to feed a camera, but how do you make an exception for a little bit of it?
If they have developed materials that bend light in ways that appear to violate the laws of physics, then it means the laws of physics need to be redefined. That's what science is. Formulas made from observations. New observations may modify your existing understanding of how things work.
And if you can't accept that, you shouldn't call yourself a scientist.
Their acoustic meta-material uses resonant cavities. The problem with it is that resonance works perfectly for a specific frequency and not at all for different frequencies.
A sonar cloak made of this material would be the equivalent of an invisibility cloak for people that are only capable of seing in a very narrow spectrum of Red: worthless if your enemy can "see" in more than one frequency.
No, you are missing the point. We will liberate the whales, and then equip them with lasers, so we won't need a Navy!
They should make the subs sound like whales... Imagine the face on sailors of Japanese whaling ships when they fish out a nuclear sub. Woot!
My first thought (aside from "invisible" submarines) is what this could do for kidney stones... Somebody with more knowledge on the subject may want to check my reasoning (the best part of /.), but I would think that better-focused ultrasound could really cut down on "collateral damage" from breaking up kidney stones, possibly allowing the technique to be used more effectively on a wider variety of cases.
Yeah, you're right - because we can't be guaranteed that everyone else won't also do the right thing means we should never undertake any actions to behave responsibly ourselves.
When did Americans' morals get so fucking twisted?
They've already managed to vanish the subs from the original article it seems. Must be the refracted light and sound that completely goes around it. Or have they dived? I think I saw a periscope!
Maybe they are just hiding from the sharks.
They will still have to de-cloak to fire their torpedoes ...
its just waves. if they can create antiwaves in noise canceling headphones on the fly, surely they can create antiwaves in water near the "tailpipe", especially since the noise source is probably relatively unchanging and well characterized
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Wrong again. We equip the whales with the lens-thingy, sonar gets bent around them, they won't get hurt, the environmentalists are happy. Then we equip them with lasers. Stealthed killer whales with friggin' lasers, dude. World domination, here I come. Muhahhahahahhaaaaa.....
Ubi solitudinem faciunt, pacem appellant.
who thought this was about Speakers for car stereos?
Thank god its friday... my thought process is shot.
Oh and I didn't bother to RTFS
Stupidity only gets you so far, then you've gotta try
I fold, you win the Internets.
It's pretty rare that submarines are identified through active pinging, because, once you ping, everyone knows where you are. Instead you try and listen for other people, and that means machinery and cavitation. I could see using this technology to dampen expected sounds from internal machinery, but that would only work so long as the machinery actually makes predictable sound and one has to wonder if this technology would actually be better at damping than other technology. In any case, its certainly not going to hide that propeller!
This is my sig.
Submarines use electric motors. Non-atomic subs use diesel generators when they are near the surface. They only use the generators when they aren't worried about being detected by sonar. The loudest noise they make is the swishing of their propellers through the water. A diesel-electric sub is nearly inaudible. The Soviet subs on the other hand; everybody in the Atlantic knew the moment those subs left port.
A wily submariner is already an expert at being invisible by hiding below abrupt changes in the water's density (caused by temperature or salt concentration).
BTW. The reason we use mostly passive sonar is that if you are pinging, everybody knows exactly where you are.
I share a similar view. There's so much of "do as I say, not as I do" coming from the mouths of political leaders.
The lack of solid logic is distressing, For example:
"Our enemies might be developing nuclear weapons." "Aye, then we must do so. We can't be at a disadvantage." has always sounded to me a lot like:
"Our enemies might be doing naughty things with farm animals." "Aye, then we must do so. We can't be at a disadvantage."
*grin*
"Ultrasound" (generally understood as meaning sound of a frequency too high to hear... i.e. more than 20khz) is pretty well useless in submarine detection, as high frequency sound has a very, very short propagation range in water. If they get to the point where they can do this with some frequency range that can go more than a few meters without being attenuated, then color me interested. But I'm guessing that would require an apparatus so huge that you wouldn't be able to deploy it anyway - the resonant cavities have to have a size of the same order of magnitude (maybe 1/4 wavelength?) of the sound wavelength... and for frequencies with any hope of propagating far (you're typically talking from 60 Hz to a few Khz), the wavelengths are HUGE - around 25 meters for 60 Hz. Bear in mind that you apparently need an array of these cavities, so you're talking about a rather enormous system.
Someone's already come up with it - the AN/SQS-53. No link, as for obvious reasons the Navy is not keen on talking about the operating frequencies of its gear, but it's well known that it uses multiple frequencies around 3.5 KHz for active sonar, and it's got a passive sonar capability to detect between very low and rather high frequencies.
I know, replying to myself is bad form, but... various navies also use anechoic coatings that are conceptually similar to this. The difference is that they are tuned to absorb incoming active sonar pulses of a frequency that you think your enemy is likely to use. They also have an effect of muffling any sounds radiating from your own boat.
Sounds great! Now, can we make sure we don't have any spies in the Navy or the Military Industrial Complex who will sell the technology to the Israelis, the Iranians, the North Koreans, the Chinese, the Russians or anyone connected to Toshiba?
Nothing to see here but us trolls...move along...
You need to consider two cases: active sonar (in which the searching ship is attempting to ensonify the target ship with sonar pulses, and then detect returning echoes) and passive sonar (in which the searching ship is just listening for sound emanations from the target). In the first case, you typically wouldn't be able to identify the submarine from a gap in return from the seabed - most of the energy in a sonar pulse ends up being entrapped in one or more "sound channels" in the water column, and never makes it to the seabed (exceptions apply, for certain water depths, etc, but still, so much sound is lost all the time that you couldn't use this... you'd get false alarms continually). In the second case, there are no real independent sources of sound that could be blocked by a passing submarine that you could use to detect them (or we'd be doing this already). So realistically, this is probably not a viable means of detecting a submarine.
At frequencies actually usable for submarine detection, this apparatus would have to be freakin' enormous - the cavities would need to be on the order of the same size as the wavelength... so you're talking meters in diameter. And you apparently need an array of them. I don't think that's something you can drag around on your submarine.
Not to get into a credentials war, but (former surface ship ASW evaluator) (have a masters degree in anti-submarine warfare from the Naval Postgrad School)
You don't need a metamaterial based apparatus like this to accomplish that - you just need an anechoic coating... which we already have.
I have it on good authority - I know someone who, in the early eighties, was in the "Hunt for Red October" command (COMOCEANSYSLANT) - who tells me that all a sub needs to do is drop below a cold current in the ocean, and they're invisible.
What's more important is silence on the sub - she also told me about them finding a Soviet sub because of a noisy coffeepot (for real).
mark
If I could do something to make loud subwoofers on the street inaudible from my house, I'd pay probably $15K to install it on my property. Should operate on the same principle, though I imagine the wavelength could be a problem due to the targeted frequency band.
If I could do something to make loud subwoofers on the street inaudible from my house, I'd pay probably $15K
12 gauge shotgun. I'll let you know where to send the money.
Have gnu, will travel.
One of the primary functions of government is to provide for the common defense of its citizens. Nice try, but FAIL.
If you suspect a threat is on a given axis, you fire a shot (or war shot) down that bearing. The target (if real) will either sit there or move, or return fire and move under the cover of noise of the real and decoy torpedoes.
However, if you suspect a threat is in your baffles, release SAND. Not just sand spray, but sand dispersed from trailing tubes to CLOG UP THEIR TUBES. This might only work if the threat is within the dispersal cone of the tubes.
Fire noise makers operating on various wavelengths/frequencies. Either the personnel will be affected to the point of being pissed of enough to move quickly , or someone will make some costly mistake.
Release oil (if the threat is on the same plane or slightly above (assuming your own sub has no detection gear atop the sail/mast) to clog up those acoustic-reshaping tubes.
Periodically release "sentries" that are tethered to and powered by trailing wires, and which will detonate if multiple nodes (operating on different sets of search parameters so as to not be deceived in multiple, simultaneously) detect a penetration of the boundary. These, obviously, will create a security "bubble" around the boat and offer such protection as detection and exposure, or detection and damaging. If said charges are properly "tuned" they then will damaging the otherwise advantageous "tuning pipes" of any sneaky-ass boats getting within range that the wire-trailing sub's government can afford to deploy. Such damage inflicted on the enemy sub need not sink it initially - just make the fucker WHISTLE at evasive speeds so as to make the fucker back of and go home, or start a war by aggressive/annoying posture.
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
When we realized that the world was a very harsh place, and that survival meant making tough decisions based on pragmatism instead of a kumbayah ideology and pacifying the citizens of San Francisco.
There already is technology that can help you there. Its called Active Noise Cancellation: http://en.wikipedia.org/wiki/Active_noise_control
They already have the ability to do that for your house, I have no idea how much it would cost or what it would involve, though. You could try to get yourself a noise cancelling headset. That might work.
Imagine letting em see you, then quickly tuning the lens, moving in closer, then firing a torpedo just as they see the whites of your eyes? Classic.
It doesn't help when your entire room shakes from subs in the apartment next door...
Thanks...Noise canceling headsets don't work for that variety of sound. I have found that earplugs (like those used in industrial settings) work very well. Of course, earplugs or noise-canceling headphones make it more difficult to carry on a conversation with your wife during dinner...
Batman is not gonna like it, that's for sure.