Invisibilty cloaks

[Broomstick]

The microwave- and light-bending materials would be awesome to use on things like tanks, though, to make them more surviveable against helicopter gunships, missiles and other tanks. But of course we run into the same problem: price. If you can buy a company of tanks for the price of fitting one with superstealth armor, then it's kinda moot to use it.

The problem isn't price - it's that you can't hide where a tank has been. Just bomb where you see the tracks end.

[salm]

The microwave- and light-bending materials would be awesome to use on things like tanks, though, to make them more surviveable against helicopter gunships, missiles and other tanks. But of course we run into the same problem: price. If you can buy a company of tanks for the price of fitting one with superstealth armor, then it's kinda moot to use it.

The problem isn't price - it's that you can't hide where a tank has been. Just bomb where you see the tracks end.

That was my point, but i thin PeZook meant that image recognicion missiles won't be able to hit tanks, simply because there is no image to recognize.

[BountyHunterSAx]

The microwave- and light-bending materials would be awesome to use on things like tanks, though, to make them more surviveable against helicopter gunships, missiles and other tanks. But of course we run into the same problem: price. If you can buy a company of tanks for the price of fitting one with superstealth armor, then it's kinda moot to use it.

The problem isn't price - it's that you can't hide where a tank has been. Just bomb where you see the tracks end.

That was my point, but i thin PeZook meant that image recognicion missiles won't be able to hit tanks, simply because there is no image to recognize.

Further, just like the problem with Yahoo CAPTCHA's, once the machine knows to look for tanks *or* surrounding signs of tank tracks and destruction, it'll be able to lock on almost as well (presuming strong image recognition capabilities in the first place).

-AHMAD

[Sarevok]

Correct me if I am wrong but is not the most widely used anti tank weapon the RPG ? Even the common guided variety ATGM seem to be old missiles requiring command input. No insurgent force in the world has wide access to "fire and forget" missiles like Javelins. Spoofing a missile is not going to work when the enemy uses weapons so backdated they don't have the proper electronics to be spoofed.

Plus there is the fact tanks have really really massive engines. Would not they shine like a flashlight to anti tank teams equipped to see in IR?

[Sikon]

Such an illustration is rather different from the silly way in which some hype seems to be treating this, as if one could just put an unrealistically-thin coat of material like paint onto a person's suit or a tank, implausibly having merely that grant "invisibility." (No doubt, putting the person inside a big thick negative-refraction metamaterial lenses assembly would sound less cool than a Harry-Potter-like cloak).

No simple material in nature has a negative index of refraction, but a structured metamaterial (or structure arranged as a photonic "crystal") obtains such. The dimensions of the structure and its necessary complexity per unit volume depends on the wavelength of electromagnetic radiation it is to work on. For visible light with wavelengths of a fraction of a micron, that means details with dimensions like this:



Manufacturing something with precision complexity on that scale is a little analogous to producing computer chips in the cost per square millimeter, let alone the challenge of trying to do it in 3D. (For example, if affordable manufacture of 3D structures with submicron-level complexity over large volumes like cubic liters was practical with today's technology, computers would have memories on the order of millions of terabytes instead of current capabilities).

The total thickness of the device is about 800 nanometers

It's no coincidence that such is on the order of that scale rather than on a much larger dimension like centimeters with billions of times the volume of manufactured metamaterial structure needed. The latter becoming affordable is quite a ways from current technology. Nobody's going to be optically cloaking a mouse, let alone a human, in the foreseeable future with optical metamaterials.

However, there are some near-term potential applications of optical negative-refraction devices on a small scale such as in telecommunications, optical computing, or tiny superlens which could exceed the ordinary diffraction limit for a microscope or optical lithography.

In contrast, to make a large object "invisible" to microwaves like radar is more practical on the macroscopic scale. Such can be done with billions of times less complexity per unit volume, since the wavelengths involved can be thousands of times greater (like millimeters or centimeters instead of a few hundred nanometers). There have been macroscopic metamaterial arrangements made working against microwaves, like this random illustration:



The very first metamaterials, working on microwaves, consisted of arrangements of copper rings and wires.

One could imagine some applications of a microwave "invisibility cloak," military and otherwise, if something worked well enough against enough frequencies of concern.



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Having a visible-light invisibility cloak for a person remains an interesting fantasy, though.

There is another way for active optical camouflage ... not perfect but more potentially affordable and workable on that scale. There can be a thin flexible display showing the background so the person blends into the scenery. Of course such is rather limited with current display technology:



In theory, implementation could someday be improved, eventually including 3D-appearing holographic images produced by phased array optics, instead of a two dimensional image. Such could work for observers at varying viewer angles and distances. The bulk of the basic technology to do that may be developed over time as a side effect of progressing towards 3D displays* for computer monitors, TVs, etc ... maybe a moderate number of decades away?

* (The 3D just references the appearance of the image, a little like a current hologram label placed on a piece of paper is a thin object but appears to have more depth, appropriately varying in appearance when seen from different angles).

Rather than requiring manufacturing a big 3D block of nanoscale metamaterial structure impractically surrounding the person, PAO emitters could be on a primarily two-dimensional (thin) surface, even a thin flexible cloak, emitting the right amounts of light in the right directions under very sophisticated computer control. However, that's still beyond practical with current technology.

In the nearer-term, more imperfect 2D-image-based active optical camouflage might still reduce detection range, though. For example, that might especially apply if trying to make more invisible a small moving combat drone, which might be almost a blur already anyway, like a prior post discusses.

Even with advancement, the tendency would be for anything to be seen through with the right multispectral imaging equipment. But something somewhat effective against the unaided human eye is conceivable. And perhaps in the future as well as now, not everybody will be walking around looking through IR-goggles all the time, to say the least.

[Admiral Valdemar]

There are already plans to implement metamaterials in servers for the Internet, to remove certain steps done today by electronics and make the whole system more efficient.

[Sikon]

Edit: Regarding active optical camouflage:

Also, emitter elements or pixel-equivalents even on a scale like 100 micron dimensions each could be decent against the human eye in some applications since one can barely see 0.1mm detail from more than close range. Submicron structure on the scale of the wavelength of visible light is not needed for some basic effectiveness, reducing by orders of magnitude the complexity needed.