Metamaterials

[Ivan Tuzikov]

Metamaterials (from the Greek word "meta-", μετά- meaning "to go beyond") are smart materials engineered to have properties that have not yet been found in nature. They are made from assemblies of multiple elements fashioned from composite materials such as metals or plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable to manipulate electromagnetic waves: by blocking, absorbing, enhancing, bending waves, to achieve benefits that go beyond what is possible with conventional materials.

Appropriately designed metamaterials can affect waves of electromagnetic radiation or sound in a manner not observed in bulk materials.^[3][4][5] Those that exhibit a negative index of refraction for particular wavelengths have attracted significant research.^[6][7][8] These materials are known as negative index metamaterials.

 

Is it possible, for example, to build a hull of spaceship and a communication dish from some alloy which does not need application of any metamaterials because the very material of hull (or dish) has nanoscale engraving (mesh structure) that provides stealth capabilities in some part of E.M. spectrum?

[Klaynos]

In that case the very material of the hull as you put it would be the metamaterial. If it was nanoscale then it would probably be in the approximate range of the visible spectrum.

 

Also, if you quote large sections of wp it is good form to reference and link to it.

[Ivan Tuzikov]

So, metal of the hull can become a metamaterial if it has engraving that reflects some part of the E.M. spectrum? And one does not need to apply anything on the metal to achieve metamaterial wave reflection properties?

[John Cuthber]

The hologram on a credit card (or even some Christmas wrapping paper) is a metamaterial. The reason it reflects light that way is not the material, but the arrangement.

The article is misleading in saying that they are not found in nature.

https://en.wikipedia.org/wiki/Structural_coloration

[Klaynos]

So, metal of the hull can become a metamaterial if it has engraving that reflects some part of the E.M. spectrum? And one does not need to apply anything on the metal to achieve metamaterial wave reflection properties?

Without very discussing details it's difficult to give any details but I don't see why not in principle. My PhD was in metamaterials.

[Ivan Tuzikov]

Without very discussing details it's difficult to give any details but I don't see why not in principle. My PhD was in metamaterials.

 

Very good. Here are some details: Is it possible to construct a spacecraft with communication antennae fully invisible in optical spectrum? Are there any limitations on the size of an object to be hidden from visual or any other range of E.M. waves?

 

Thanks in advance for Your time.

[Klaynos]

It is not an unreasonable concept.

 

What I would say is that we're quite a way from broadband, visible spectrum metamaterials for any purpose let alone invisibility. It may prove to be impossible but I'd assume from what you've said that this might be for SciFi writing? And it's certainly not a completely crazy idea.

[Sensei]

Is it possible to construct a spacecraft with communication antennae fully invisible in optical spectrum? Are there any limitations on the size of an object to be hidden from visual or any other range of E.M. waves?

 

Transmission from spacecraft is not in visible spectrum.

 

Spacecrafts to communicate in power saving mode are utilizing directional antennas.

That's it: if your receiver does not have the right settings (angles, position of Earth, time) when transmission arrives, it will miss it.

 

Similar like laser is emitting photons in one direction.

If you're not on path photons will be traveling, you will miss it.

You can even not know it's emitting photons.

[Endy0816]

I think he means if the antenna itself could be hidden.

 

We can hide small objects for specific wavelengths. I haven't heard of anything visible spectrum though.

 

I'm guessing we're talking fictional spaceship battles in which case metamaterials capable of this would not be an unreasonable advancement.

[Enthalpy]

Is it possible to construct a spacecraft with communication antennae fully invisible in optical spectrum?

A first step is a cigar antenna. Apart from the wave launcher which can be inside the craft, it's made of dielectric only which can be transparent: silica, polystyrene, polymethylpentene...

 

Light reflection at the surface can be minimized by an antireflection coating, even over a decent bandwidth.

 

What stays is the refraction by the transparent material, made worse as you probably need an array of cigar antennas. It will be as visible as a rod of glass in air.

 

Alternately, a reflector antenna can consist of thin metal wire which reflects less light than plain material. Paint the wires.

 

Ahum. I strongly doubt that satellites can be made undetectable. Well visible in the sky, uncapable of manoeuvres, fragile, they're sitting ducks.