BAE Systems said it has successfully tested an ‘invisibility cloak’ that allows a vehicle to camouflage into its surroundings. The system, which can work over infra-red and other frequencies, will be displayed in infra-red mode on a BAE Systems CV90 armoured vehicle at the UK Defence and Security Equipment International exhibition later this month.
Known as “Adaptiv”, the patented technology is based on sheets of hexagonal ‘pixels’ that can change temperature very rapidly. On-board cameras pick up the background scenery and display that infra-red image on the vehicle, allowing even a moving tank to match its surroundings. Alternatively, it can mimic another vehicle or display identification tags, reducing the risk of fratricide.
Current work focuses mainly on the infra-red spectrum, as this is most important to the Swedish Defence Materiel Administration (FMV), which funds part of the work. However, BAE Systems engineers have combined the pixels with other technologies, which provide camouflage in other parts of the electro-magnetic spectrum at the same time to provide all-round stealth, which will be developed further over the next few years.
Trials by BAE Systems in mid-July showed that one side of a CV90 could be made effectively invisible or appear to be other objects, including a 4×4 vehicle, when viewed in the infra-red spectrum.
Project manager, Peder Sjölund explains: “Earlier attempts at similar cloaking devices have hit problems because of cost, excessive power requirements or because they were insufficiently robust. Our panels can be made so strong that they provide useful armour protection and consume relatively low levels of electricity, especially when the vehicle is at rest in ‘stealth recce’ mode and generator output is low.”
He adds: “We can resize the pixels to achieve stealth for different ranges. A warship or building, for instance, might not need close-up stealth, so could be fitted with larger panels.”
Even researchers from Boston-area Fractal Antenna Systems, Inc., reported early this month of additional measurements that confirm its claims of a working ‘invisibility cloak’.
In March, 2009, the firm’s research group disclosed the first invention of the invisibility cloak. It had unprecedented ability to work ‘wideband’ and render an object invisible to microwaves. The wideband aspect also demonstrated a path for making invisibility cloaks in the full spectrum of visible light.
A previous invisibility cloak effort by Duke University-based researchers had shown some degree of cloaking , but over a narrow frequency band. That cloaking also rendered the object partially detectable/visible by the presence of shadows.
The firm’s unprecendented invisibility cloak uses layers of state of the art metamaterial, made from self repeated designs called fractals. The layers surround the object to be cloaked like an onion skin. The microwaves slip stream around the object and its cloak layers.
The new measurements by the firm’s researchers concentrate on the scattering, which details how much of the impinging waves bounce off the sides, the front, and the back of the invisibility cloak. Previous reports showed how the area in back of the cloak acts in a ‘see around’ fashion, as expected. The new measurements show additionally what happens to the waves when viewed from the sides and towards the front. A true invisibility cloak must ‘scatter’ these waves in a minimal way, as if no obstacle was there at all. The new measurements confirm this minimal scattering behavior, which is essential for true invisibility.
Using copper layers in place of the invisibility cloak, an experimental ‘control’ demonstrated the effect was not a remnant of some other effects: the control showed substantial shadowing from the back and the sides, which amounts to significant scattering.
Notes inventor Nathan Cohen: “The scattering profile matches an empty-space one with good to high fidelity. It’s as if there is nothing there. In particular we see no shadows. Substantial shadowing was present with the control. It is a striking difference and confirmation.”
The wideband invisibility cloaking is enabled with the firm’s proprietary fractal metamaterial technology. The firm now uses the technology in several of its products, unrelated to cloaking. Cohen cautioned that the invisibility cloak is a technology demonstrator and not a practical device. “You can’t hide a starship or a battleship in it,” he remarked, “but we now have to ask where such cloaks can be useful rather than merely intellectually amusing.”