Posted on 01/05/2011 8:49:16 PM PST by decimon
CHAMPAIGN, Ill. — In one University of Illinois lab, invisibility is a matter of now you hear it, now you don’t.
Led by mechanical science and engineering professor Nicholas Fang, Illinois researchers have demonstrated an acoustic cloak, a technology that renders underwater objects invisible to sonar and other ultrasound waves.
“We are not talking about science fiction. We are talking about controlling sound waves by bending and twisting them in a designer space,” said Fang, who also is affiliated with the Beckman Institute for Advanced Science and Technology. “This is certainly not some trick Harry Potter is playing with.”
While materials that can wrap sound around an object rather than reflecting or absorbing it have been theoretically possible for a few years, realization of the concept has been a challenge. In a paper accepted for publication in the journal Physical Review Letters, Fang’s team describe their working prototype, capable of hiding an object from a broad range of sound waves.
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.
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The cloaking technology also may affect nonlinear acoustic phenomena. One problem plaguing fast-moving underwater objects is cavitation, or the formation and implosion of bubbles. Fang and his group believe that they could harness their cloak’s abilities to balance energy in cavitation-causing areas, such as the vortex around a propeller.
(Excerpt) Read more at news.illinois.edu ...
Not from my training and experience. Our subs are VERY quiet, too quiet for our OWN sonar if they are running deliberately 'quiet.' They do that any time they are in tactical combat.
But sure - if they are doing 'flank speed' underwater, they do make a whine that is audible - IF your ship is listening with the right equipment (rarely done continuously.) But, you won't find any sub captain doing flank speed in most combat situations - because he knows he would be a fool to do so.
Noise created by a sub is not even part of sub detection now-days - surface ships worry far more about temperature layers beneath the surface that bend sound waves - and even hide subs altogether - for long enough to 'get away.'
Tomorrow’s headline — “President Obama signs order to scrap all US submarines.”
Why bother to repeal DADT if you're going to scrap submarines?
You’re only saying that because they’re [old joke omitted to avoid getting banned].
Is the FleetASW base still around in San Diego?
Hey guys, thanks for the info.
I’m glad to know how that ping thingy works. I think my pings here on FR are broke, sometimes, LOL.
Seriously, the only thing I know about submarines is what I’ve read in novels or seen in movies. (Yeah, I know - great source for factual info, right? LOL)
I love stories about subs. That started when I was a teenager and read “Run Silent, Run Deep” and “Up Periscope”.
And one of my favorite movies is “The Hunt for Red October” with Sean Connery.
(here’s a trailer if you haven’t seen the movie)
http://www.imdb.com/video/screenplay/vi334758681/
(Of course, I haven’t seen or read any Tom Clancey stuff that I didn’t like, heheh.)
;^D
It’s there for Surface ST’s and Coast Guard. All Submarine schools moved back to Groton in 91-94.It’s a shame too, one of my Favorite things about PCS orders to a school in San Diego was the drive there from Groton, and a stop at the Big Texan in Amarillo.
The enviroweenies will never let this stand. “What about the whales? [sobs hysterically] They’ll be running into these submarines and dying like flies!@1@!@1!#2$@$#@!”
My next cat’s name: Nicholas Fang
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