Invisibility technologies conceal vehicles from sensors
The ultimate stealth protection for anything on or over a battlefield would be the ability to disappear from view, leaving no visual, electronic or infrared (IR) signature for an enemy to detect.
Work is underway to develop technologies that conceal, cloak or otherwise make objects appear to vanish. In many cases, the value of these technologies is in their ability to dupe an enemy into thinking he sees something besides a threat or potential target—background vegetation, for example, or an innocent vehicle. Even if the image an enemy detects only confuses him for seconds, it could be enough time for a friendly force to evade fire.
There are a number of invisibility research—or, more accurately, cloaking—projects attracting interest and funding from militaries and other organizations around the world. Two in particular have come to the fore: the Adaptiv Active Defense System fromof the U.K., which uses IR cloaking technology and is reportedly within two years of being production-ready for use on ground, air and sea vehicles; and the Black Fox electronic thermal IR countermeasure system from Eltics Ltd. of Israel, which is likewise designed to make vehicles invisible to thermal sensors.
These technologies represent real-world solutions to concealment. They are designed to counter IR surveillance and targeting technology by confusing remote sensors, including those on unmanned aerial vehicles (UAV), heat-seeking missiles or in use by gunners with thermal vision systems. They would not be effective against a squad of soldiers or an observation team that maneuvered near enough to observe a target with their own eyes.
These approaches contrast with what most scientists are doing in cloaking research, which typically involves devising techniques for manipulating electromagnetic waves of visual light to conceal 2-D and lately 3-D objects. This usually involves “transformation optics,” which bend electromagnetic waves and control the emission of light from an object. Other researchers use metamaterials, man-made composites that derive their properties from nano-scale structures rather than their composition, to alter the path of light and conceal objects. Some work involves so-called cloaking carpets that hide objects from IR radiation and microwave detection, again by bending and warping emissions around or away from objects.
These efforts are lab scale and usually involve experiments on microscopic objects, some as small as 1 micrometer. Most of this research is less than a decade old—some trace its origin to two peer-reviewed papers that were published in U.S. scientific journals in 2006. Initial results have been encouraging, with many teams able to lay experimental foundations that demonstrate the scientific validity of their work. Where this research will go in terms of practical application is anyone's guess. Some maintain it will be years before what is being done in laboratories will appear in real-world situations.
A few techniques used to cloak objects from detection could be applied in other areas of interest to the military, such as microelectronics or solar energy. In some cases the methods in use to alter the movement of electromagnetic waves, IR or microwave emissions could be applied to divert heat from sensitive electronics, or focus sunlight in solar panels for greater energy yields. Invisibility research, in other words, will have a ripple effect beyond battlefields that improves the performance of diverse applications.
BAE began research on the Adaptiv Active Defense System with the Swedish Defense Materiel Administration a decade ago, after Sweden's military determined that IR sensors and weapons were emerging as major battlefield threats. The system has proven its potential as an IR cloaking technology in tests on a CV90-120T light tank, which is manufactured by Swedish subsidiary BAE Systems Hagglunds and is in use by the Swedish army.
Adaptiv counters IR sensors and weapons by changing the temperature of a vehicle to mimic the heat signature of its surroundings, rendering it invisible to thermal sensors, guidance systems and even night-vision goggles.
The Adaptiv system can also be used to project images on the side of a vehicle. According to BAE representive Mike Sweeney, images include background vegetation, passenger cars and even animals.
All of this is possible through the use of hexagonal metal tiles with surface dimensions of 14 cm (5.5 in.) and thicknesses of 2-3 cm. The tiles, which have a foam core and microelectronic circuitry, are mounted on the external surfaces of the CV90. Sweeney says the circuitry is powered by the tank and regulates the thermal signature of the vehicle through the tiles to match its surroundings.
The tiles also act much like “pixels,” Sweeney says, in their ability to project images that have been captured and transmitted by the tank's IR sensors. “The tiles turn a vehicle into a big infrared TV,” he remarks. BAE is working on a thin-film covering for the tiles that would enhance images projected on them, though details are not being released.
Sweeney says a CV90-120T tank will generally require 1,000-1,500 tiles for cloaking. The tiles are designed for easy mounting and replacement if damaged. To protect against friendly fire, identification-friend-or-foe sensors can be inserted within the tiles or on top of a vehicle.
One non-camouflage benefit they provide, he notes, is an extra layer of armor, albeit with a “relatively small increase in weight.” The CV90-120T weighs 32 tons without the tiles. Sweeney didn't estimate how much weight the tiles add, or speculate on how effective the added protection might be.
Despite its apparent effectiveness in tests, the Adaptiv system requires some engineering advances from the vehicles it would be used with. The CV90-120T, for example, already has the electronic architecture, computer system and sensors necessary to operate the system. Sweeney also says the tank has various sound-dampening components, and the exhaust system is fitted with a heat exchanger and other devices that minimize its thermal signature.
“These other technologies are necessary for the Adaptiv system to work effectively,” Sweeney notes. “There is no one technology we are aware of that by itself acts as a magic bullet” for cloaking a vehicle's IR signature.
Tanks aren't the only platform targets for the technology. BAE says it could also be used on ships and helicopters to minimize their IR signatures. While the issue of added weight would be significant for a helicopter, Sweeney says that due to its altitude and distance from most threats, a helicopter would require far fewer tiles to dupe an IR weapon or sensor than a ground vehicle.
Eltics' Black Fox technology is also designed to adjust the heat signature of a vehicle, by taking constant readings of ambient temperature while the platform is on the move or stationary. The technology is also capable of simulating the thermal signatures of non-threatening vehicles, by applying them from a preprogrammed database. Eltics says that a main battle tank can be made to look like a Humvee or pickup truck to an IR sensor.
The technology uses a scanning Flir (forward-looking IR) camera mounted on top of a vehicle to record a 360-deg. thermal image of its surroundings. Computers in the vehicle process the images and the data is transferred to “active plates”—described as thermoelectric modules in patent literature—that are attached to the platform. The plates, which come in different sizes, duplicate the thermal texture of the vehicle's surroundings, altering its IR signature and making it invisible to sensors.
The idea is to make a vehicle disappear by duplicating the thermal signature of its surroundings. To maintain constant contact with the surroundings as a vehicle moves, the Flir camera has a pan-tilt sensor that detects gradients and adjusts for them to remain focused on the vehicle's background.
The vehicle computers—there are two: a main computer unit and a central control unit—that control the system also have a database that records the thermal signatures of different vehicles. These can be called up and projected on the plates to create fake situational awareness and confuse an enemy.
The patent literature records another capability of the Black Fox system: the ability to visually capture the percentage and pattern of a background and apply its appropriate thermal signature gradients on the plates for complete concealment if a vehicle stops.
The Black Fox system can be applied to a range of vehicles—tanks, armored personnel carriers, ships and helicopters among them. Importantly, it can be used with any type of armor including reactive suites.