By David Crane
defrev (at) gmail (dot) com
June 16, 2009
It looks like the whole metamaterial/negative-index material movement just got another shot in the arm with the development of an "acoustic metamaterial lens" that can theoretically create an acoustic/sonic "invisibility cloak" a.k.a. "cloak of silence" capable of hiding military submarines from enemy detection. DefenseReview first reported on metamaterials a.k.a. negative-index materials or "negative index metamaterials" in August 2006. The technology on which we were reporting at the time theoretically has the potential to lead to an optical invisibility cloak for cloaking soldiers and military equipment and vehicles.
Anyone who's seen the film the The Hunt for Red October remembers the very cool, ultraquiet "caterpillar drive" that the Russian Submarine "Red October" utilized. It would seem that the Red October's "caterpillar drive" was essentially a magnetohydrodynamic-drive/MHD propulsor engine that used a electromagnetic field to drive the sub without using any moving parts, rather than using a mechanical propellor. Anyway, as revolutionary as that fictional submarine magnetohydrodynamic propulsion system may have been, it was arguably somewhat more conventional than, and very different from, an "acoustic invisibility cloak" since it quieted the submarine organically and didn't shield the sub from enemy sonar detection equipment.
Acoustic cloaking via an acoustic metamaterial lens is reportedly a "next step" technology that can theoretically create an active anti-sonar-detection system for future U.S. military submarines. Three researchers out of the University of Illionois at Urbana-Champaign Mechanical Science and Engineering (MechSE) department are claiming credit for the acoustic metamaterial lens tech. They are Assistant Professor Nicholas Fang (Nicholas X. Fang), Shu Zhang, and Leilei Yin.
The "acoustic superlens", or ultrasound lens, that they're developing reportedly can be used for medical acoustic imaging as a kind of enhanced ultrasound to better detect tumors and other physical abnormalities, but we hear at Defense Review are interested in the potential military applications of the technology. One question we have is if the technology is so viable for military future applications, including submarine warfare applications, why hasn't it been classified already and/or turned it into a black program? DoD is usually pretty diligent about that. Perhaps they're just waiting for it to be developed to the point it can actually be applied to submarines before classifying it.
So, is the acoustic cloak hype or the real deal? Time will tell, and we'll be watching. It is, however, ironic that three Chinese (or Chinese-American, whatever the case may be) researchers may have just provided the U.S. military with an important strategic technology solution to the growing Chinese military threat, especially since China is currently in the process of significantly expanding its naval warfare capabilities. China is, after all, arguably our largest and most dangerous potential future nation-state enemy.
Nicholas X. Fang
4414 Mechanical Engineering Laboratory
1206 West Green Street, MC-244
Urbana, IL 61801
http://www.mechse.illinois.edu/research/nicfang Research Website
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