Professor Pendry believes scenes like this are now a real possibility

In the end, Yehudi was not put into production because better radar had already enabled Navy warplanes to regain the tactical advantage, but the idea was revived after air battles over Vietnam. Concerned that the formidable F-4 Phantom could be seen at a greater range than its much smaller Russian adversary, the MiG-21, the Pentagon initiated a programme code-named Compass Ghost. An F-4 was modified with a blue-and-white colour scheme and nine high-intensity lamps on the wings and body reducing the detection range by as much as 30 percent. The name compass ghost grey is also associated with warplane paints.

And of course, there is that enduring 1943 mystery dubbed the ‘Philadelphia Experiment’. Here the US Navy is alleged to have made an entire warship (USS Eldridge) disappear in Delaware Bay, in full view of hundreds of witnesses, by using some type of radio frequency waves. The USS Eldridge was a 1240-ton Cannon class destroyer escort built at Newark, New Jersey, and commissioned in August 1943. She was employed on escort duties in the Atlantic until May 1945, when she departed for service in the Pacific. Eldridge was decommissioned in July 1946 and placed in the Reserve Fleet. In January 1951, she was transferred to the Greek Navy, in which she served as Leon into the 1990s. Though an utterly fascinating story, it’s definitely more science fiction than scientific fact. Back to the Brits, the Cold War and a spot more research on special paints...

At the height of the Cold War some analysts believed that in the event of conflict, Soviet tanks could roll through Western Europe and be on the docks of Calais, France, in about 10 days. If the Cold War turned a little warm, and a conventional war ensued, tanks were regarded as every bit as important as missiles and men, and the Soviets had lots of them. Britain’s military boffins were asked to commission a study on how best to camouflage NATO tanks. Lots of colours and mosaic patterns were tried, but again, they could not disguise the tank’s outline against a battlefield horizon, especially a flat one, or when back-lit by the sun. So British engineers chose to cover a tank with hundreds of light bulbs. When these lights were adjusted to the ambient light level of the back-lit sky, the tank became virtually invisible to a distant observer - some say even with the use of binoculars.

F-117. One of the best radar avoiding aircraft ever built. Surprisingly, the USAF announced its retirement in 2006.

By the late 1970s an early wooden-framed prototype of Lockheed’s Stealth fighter had already risen from drawing board and a few years later, under the code-name Have Blue, the aircraft was flying. With its unique radar absorbing outercoating, low radar signature, the US had created an almost invisible aircraft... but the F-117 or “wobbly goblin” as its pilots called it, was invisible only to radar.

In the early 1990s the US military again experimented with electrochromatic paints on aircraft but few details of its success or failure ever appeared in public. Another project known as ‘Ivy’ was also initiated that tested various colour schemes.

In 1993 adaptive electro-optical camouflage, as manifested in Project Chameleo, was introduced. Chameleo was essentially an electric “cloaking device”, designed to conceal an object from view by placing a video screen between the viewer and target. The screen would show what’s being filmed behind the object, a building for example, by use of video leads and projection. Patent holder Richard Schowengerdt, head of the project and a military researcher based in Lakewood, California, began looking into the technology as a possible way of hiding sprawling top-secret facilities. Chameleo is examining modified versions that might emit or absorb energy to minimise radar or sonar detection.

It is our understanding the Pentagon is very interested in Schowengerdt’s research.

In 2003, Professor Susumu Tachi of Tokyo University and founding head of the Virtual Reality Society of Japan, demonstrated something very similar. He used a coat with microscopic reflectors, which act like a movie screen. A video camera behind the coat was linked to a projector, which bounced the image off the front of the coat’s reflective surface. Because there is no time lag between what’s happening behind the wearer and the image cast on the front of the coat, an illusion is created that appears to allow you to see “straight through” the wearer. “This is a kind of augmented reality,” said Tachi. The coat will also reflect images when the material is wrinkled. But the reality is, the “invisibility coat” is an illusion - a camera trick.

Doctor Philip Moynihan, a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, said Schowengerdt’s idea has broad applications in medical surgery, construction and aviation, although it remains in an embryonic stage. Moynihan has been credited with coining the phrase “adaptive camouflage” as the technical term for the science of invisibility. “I think it’s got tremendous potential, once it’s refined,” Moynihan said. One of the hurdles will be to make the technology smaller, affordable and viewable with the naked eye, he added.

Moynihan said the US military has studied similar technology as futuristic camouflage for years. In the mid-1990s, he and another scientist conceived “adaptive camouflage” images for stealth or armoured vehicles that could help them blend in with any type of surroundings. “We wanted something that could adapt to changing light conditions because present camouflage can be spotted at certain angles and can be seen in infrared lighting,” Moynihan said. They never made a prototype and abandoned the project when funding dried up.

Moynihan still believes adaptive camouflage technology could one day allow soldiers to take a picture of their surroundings and digitally transfer the image using a handheld computer to the surface of their clothing.

Another use of the concept is to coat the inside of an airplane cockpit with micro reflectors. Hard or bumpy landings could be assigned to history if the crew could “see” just how far they are above the runway from a projected image. The pilots would effectively see a speeding runway under their feet!

And what of the future? In 2007, researchers at the US Department of Energy’s Ames Laboratory developed a material with a negative refractive index for visible light. Ames Laboratory senior physicist Costas Soukoulis, working with colleagues in Karlsruhe, Germany, manufactured a silver-based, mesh-like material that marks the latest advance in the rapidly evolving field of metamaterials, materials that could lead to a wide range of new applications as varied as ultra high-resolution imaging systems and yes you’ve guessed it... “cloaking devices”. The discovery received much attention in Science, Optic Letters, and Nature. Scientists believe it marked a significant step forward from existing metamaterials that operate in the microwave or far infrared - but still invisible - regions of the spectrum. Those materials were heralded as the first step in creating an invisibility cloak.

In Britain, the Ministry of Defence admitted it had been involved in an experiment involving rendering a tank “invisible” to the naked eye. Sources say the tank was coated in silicon and video projectors were strategically positioned to beam images of the surrounding countryside on to the tank. One witness to the experiment said: This technology is incredible... if I had not been present I wouldn’t have believed it. I looked across the fields and just saw grass and trees, but in reality, I was staring down the barrel of a gun.” Professor Sir John Pendry said the research programme was very good but was limited because the illusion is dependent on the quality of the cameras and projectors. He did add: “The next stage is to make the tank invisible without them - which is an intricate and complicated job - but possible. Hendry, of course, is involved in similar work to Xiang Zhang, but using microwaves.

Xiang Zhang's team have created artificial structures that can bend light

In 2008 came another announcement, the Nanoscale Science and Engineering Center at the University of California at Berkeley released a press statement on the status of a related project. Two research teams headed by Zhang and working on metamaterials, had made a major breakthrough. While one team used nanometre-scale stacks of silver and magnesium fluoride in a “fish-net” structure material looking like a miniature waffle, the other made use of nanowires made of silver. These are artificially created structures not seen in nature and developed on a nano scale, measured in billions of a metre - 0.00000066 to be exact. They have the ability to grab electromagnetic radiation and deflect it smoothly. One team member, Jason Valentine, said that while the material does not actually make objects invisible, it does affect light. “In naturally occurring materials, the index of refraction, a measure of how light bends, is positive,” said Valentine. “When you see a fish in water, the fish appears to be in front of its real location,” said Valentine. It’s the same with a stick - it will appear to bend away from you.” The team have developed negative refraction so the fish would appear above the water. He notes the illusion is strange.

Zhang’s research has constantly been associated with invisibility, but it has lots of applications in the world of medicine and science. “We are not actually cloaking anything,” Valentine said in an interview. “I don’t think we have to worry about invisible people walking around any time soon... we are just at the beginning of doing anything [or should that read - “something”] - like that.

Essentially, Zhang and his team have reached the point where they can now redirect light using the material that can “cloak” a three-dimensional object. This essentially means if you cover a vehicle with the material, your eyes would reportedly see what’s behind the car and not the car itself - an advanced form of “adaptive camouflage” perhaps. Though still a long way from creating a real “invisible cloak”, some scientists believe they have already surpassed the art of illusion. “Cloaking may be something that this material could be used for in the future,” said Valantine. “You’d have to wrap whatever you wanted to cloak in the material. It would just send light around. By sending light around the object that is to be cloaked, you don’t see it.” And it is that fact that has so interested the military and world of intelligence.

In its 2009 Budget proposal, the Defense Advanced Research Projects Agency (DARPA) plans to build “transparent displays” by “exploiting the optical plasmon phenomenology characteristics of nanoscale structures.” Not to mention “biomolecular computers.” It is part of the Pentagon’s Asymmetric Materials for the Urban Battlespace Programme’.

DARPA has millions of dollars tied-up in related projects to investigate urban obfuscants (another word for metamaterials). And a particularly interesting take on the project is an invisibility shield/adaptive camouflage shield. Xiang Zhang’s is being analysed in the hope it can be adopted to help make soldiers “invisible” in urban areas. The Pentagon also wants the shield to be “self-healing”. In other words, if the soldier did receive a gunshot wound that passed through his shield - it (the shield) would repair itself and continue to function. Similarly, the soldier could conceal and fire a weapon from behind the shield. And an added bonus - because the light is bending, a person wearing a full covering of the material would not cast a shadow.

© ESPL - Eye Spy Intelligence Magazine 2011. (Adapted from Eye Spy issue 58)