New Meta-Material Could Render Submarines Invisible to Sonar Detection

[gambit]

heh, that was a joke about this:

So where is the 'discrimination'?

Racism - Wikipedia, the free encyclopedia

In the case of institutional racism, certain racial groups may be denied rights or benefits, or receive preferential treatment.

Can you answer the question, particularly the highlighted words?

hypothetical question huh? ok, to humor you, i'll ally with which country i think is the lesser of 2 evils

Nice try at evading. But expected of a coward. By the way...

USS Chung-Hoon (DDG-93) - Wikipedia, the free encyclopedia

USS Chung-Hoon (DDG-93) is an Arleigh Burke-class Aegis destroyer serving in the United States Navy. Chung-Hoon was named in honor of Rear Admiral Gordon Pai'ea Chung-Hoon (1910–1979), recipient of the Navy Cross and the Silver Star.

 

[casual]

So where is the 'discrimination'?

Can you answer the question, particularly the highlighted words?

ya, here's your answer:
Joke - Wikipedia, the free encyclopedia
i said there was no real discrimination then i made a joke about the resent viral video on youtube. quit being all anal over a joke k?

Nice try at evading. But expected of a coward. By the way...
USS Chung-Hoon (DDG-93) - Wikipedia, the free encyclopedia

sorry dude, but i hate hypothetical questions. and if you want an serious answer, at least give some background info on how this hypothetical war started.

 

[MastanKhan]

New Meta-Material Could Render Submarines Invisible to Sonar Detection

New Meta-Material Could Render Submarines Invisible to Sonar Detection - Defense-Update

A research team from the University of Illinois, led by mechanical science and engineering professor Nicholas Fang, have demonstrated a technology that renders underwater objects invisible to sonar and other ultrasound waves.

This kind of an ‘acoustic cloak’ could be used in the future to mask submarines from enemy sonars.

While materials that can wrap sound around an object rather than reflecting or absorbing it have been theoretically possible for a few years, a prototype demonstrating such process was never realized – until now. In a paper accepted for publication in the journal Physical Review Letters, Fang’s team describe the principles used in constructing such prototype.

The cloak is made of metamaterial, a class of artificial materials that have enhanced properties as a result of their carefully engineered structure. Fang’s team designed a two-dimensional cylindrical cloak made of 16 concentric rings of acoustic circuits structured to guide sound waves. Each ring has a different index of refraction, meaning that sound waves vary their speed from the outer rings to the inner ones.

“This is not just a single wavelength effect. You don’t have an invisible cloak that’s showing up just by switching the frequencies slightly,” Fang said. The acoustic cloak demonstrated its ability to cover a broad range of sound wavelengths, from 40 to 80 KHz, although with modification could theoretically be tuned to cover tens of megahertz.

“Basically what you are looking at is an array of cavities that are connected by channels. The sound is going to propagate inside those channels, and the cavities are designed to slow the waves down,” Fang explained. “As you go further inside the rings, sound waves gain faster and faster speed.” Since speeding up requires energy, the sound waves instead propagate around the cloak’s outer rings, guided by the channels in the circuits. The specially structured acoustic circuits actually bend the sound waves to wrap them around the outer layers of the cloak.

The researchers tested their cloak’s ability to hide a steel cylinder. They submerged the cylinder in a tank with an ultrasound source on one side and a sensor array on the other, then placed the cylinder inside the cloak and watched it disappear from their sonar. Curious to see if the hidden object’s structure played a role in the cloaking phenomenon, the researchers conducted trials with other objects of various shapes and densities. “The structure of what you’re trying to hide doesn’t matter,” Fang said. “The effect is similar. After we placed the cloaked structure around the object we wanted to hide, the scattering or shadow effect was greatly reduced.” The geometry is not theoretically scaled with wavelengths.

Thomas---sir,

The american subs have been quiter than a dead man lying in his grave for a hundred years----the issue is ----how to cover for the HOLE IN THE OCEAN----THE SUBS SEARCH EACH OTHER ON THE BASIS OF THE NOISE THE OTHER ONE CREATES---I believe that this research is a diversion from the real stuff----.

Sub hunting is like the job of a sign tracker on land----. A modern sub of today may not need to use its sonar today----even if making a torpedoe shot at the opponent---.

The more important thing is to talk about the american sub technology where the operator of a sub can see in front back and on the sie of the sub in 3D in a live mode on his TV screen of what is happening outside of the sub-----that is the break through technology----not this metal thing.

 

[gambit]

Thomas---sir,

The american subs have been quiter than a dead man lying in his grave for a hundred years----the issue is ----how to cover for the HOLE IN THE OCEAN----THE SUBS SEARCH EACH OTHER ON THE BASIS OF THE NOISE THE OTHER ONE CREATES---I believe that this research is a diversion from the real stuff----.

Sub hunting is like the job of a sign tracker on land----. A modern sub of today may not need to use its sonar today----even if making a torpedoe shot at the opponent---.

The more important thing is to talk about the american sub technology where the operator of a sub can see in front back and on the sie of the sub in 3D in a live mode on his TV screen of what is happening outside of the sub-----that is the break through technology----not this metal thing.

First...About the 'hole in the ocean'...

Passive Sonar - Sonar - Core Skills - Kaon Ltd

Lofargrams - a spectral display collected over time, showing the temporal evolution of the spectral content of a signal. They generally employ high levels of temporal integration with large FFT sizes in order to extract accurate spectral content and low signal levels. These are typically displayed as waterfall spectrograms.

LOw Frequency Analysis and Recording (LOFAR). In passive sonar detection of any non-natural object, meaning something like a submarine, background noise is very important, just like the background noise in radar detection. In both situations, background noise are usually discarded in active seek mode. However, same for both situations, background noise are considered when in passive detection mode. The problem for both situations is increased data processing over time due to the amount of background noise itself.

What happens in sonar LOFAR detection is that the marine background noise literally flows over the non-natural object and through it as well. The object's material make up will create delays in propagation that will stand in contrast from the typical marine environment. Hence there is the impression of a 'hole'. This impression is partially correct as there will be some 'loss' of sort of the background noise because of absorption by the non-natural object, then some of the background noise are delayed as the signals flows over the surface of the non-natural object.

Two major issues with LOFAR are time and omnidirectional requirement. For the latter, we can live one passive detector but it will require even more time. That is why we develop something like this...

AN/SSQ-57 Low Frequency Analysis and Recording (LOFAR) Sonobuoy

The AN/SSQ-57B Low Frequency Analysis and Recording (LOFAR) sonobuoy is an A-size, expendable, non-repairable, calibrated sonobuoy. It uses the AN/SSQ-41B platform, substituting a calibrated hydrophone for frequencies in the 10Hz to 20,000Hz range. The LOFAR sonobuoy provides omnidirectional passive acoustic signature data to the monitoring unit(s). The sonobuoy is calibrated and can be used to accurately measure ambient noise, and through post event analysis, provides Sound Pressure Level (SPL) measurements.

The more of these things over an area of interest, the better the background noise analysis, especially if this non-natural object is in the middle of the array. It takes skills that must be developed over a long time to decipher the 'waterfall' lofargram to assert, really more like an opinion, that a submarine is present.

Second...This research into metamaterial for subs to escape sonar detection, even against LOFAR, is not a 'diversion'. The material can be made or 'tune' to have no delays in signal propagation on its surface AND to prevent any 'pass through' of any signals into the sub's interior, or absorption. Absent these factors, the sub is essentially 'invisible' to sonar in either passive or active mode.

 

[gambit]

I'd be far more impressed if it was a thin surface coating. As is, it would be far too large and far too structurally fragile to be used on a submarine that moves. I also think that this person, by developing a militarily relevant weapon for the US, is committing a crime against humanity. It would be like designing gas chambers for Nazi Germany.

You are still in school under daddy's money, never had a real job, and never served in the military. You are the type we do not need to 'impress'.