Barely a week goes by without researchers announcing a new ‘invisibility cloak’ or ‘cloaking device’ (depending on whether they read Harry Potter or watch Star Trek) that could potentially revolutionise the future of warfare. Strategic Defence Intelligence investigates some of the technology and whether the current state-of-the-art products have anything to offer the defence market.
Invisibility generally means rendering an object effectively undetectable to the human eye. In practical terms, it differs from camouflage by either bending light around the object so only the background can be seen, or projecting an image of the background onto its visible surface. By contrast, camouflage tends to be a static solution that uses a trick of the eye to enable an object to blend into the background.
Calcite
A recent breakthrough in achieving invisibility was announced by the Singapore-MIT Alliance for Research and Technology (SMART Centre), the University of Birmingham, Imperial College London and the Technical University of Denmark.
Instead of using artificially engineered metamaterials, which can render small objects invisible in certain wavelengths of light, they used naturally occurring calcite. Calcite has strongly refractive properties and, when two pieces are combined at the correct angle into a wedge shape, it can make an object behind it completely invisible from certain angles.
E-camouflage
As part of the UK’s future protected vehicle programme, BAE Systems is developing a system known as e-camouflage, which uses light-emitting diodes (LEDs) to project images of the surrounding environment onto the outside of the vehicle to enable it to blend into the landscape and evade attack.
While the prototype is not expected to be ready for four years, an experimental operational capacity should exist by 2013. However, the system will not be able to operate in dusty environments such as Afghanistan, as it would illuminate a surrounding dust cloud.
Metamaterials
Scientists at the University of California demonstrated in 2008 that they were able to cloak three-dimensional objects using artificially engineered materials, known as metamaterials, which redirect light around objects.
Objects appear visible because they reflect light back to the human eye. The metamaterials developed at the university curve radar, light and other waves around an object so that they do not create reflections or shadows.
The research was partly funded by the US Army Research Office and the National Science Foundation’s Nano-Scale Science and Engineering Centre.
Sonar
Underwater, invisibility from sonar is as important as that from visible light on land. Researchers at the University of Illinois have developed an acoustic cloak that makes underwater objects invisible to sonar and other ultrasound waves.
The device controls sound waves by bending and twisting them around a specially-shaped space using a unique metamaterial.
The cloaking technology could also be used to help prevent cavitation, a term used to describe the formation and implosion of bubbles around fast-moving underwater objects.
Practicalities
Currently, advances in rendering objects invisible are in their infancy. They are either restricted to concealing very tiny objects or only work in ideal conditions from certain angles.
Modern camouflage is far more effective on the battlefield, helping protect personnel and equipment from detection not just by the human eye, but by infrared sensors on weapons sites and surveillance systems such as unmanned aerial vehicles (UAVs).
In the air, stealth technology, which protects against detection by radar via the shape of the aircraft and materials used, is far more important than hiding aircraft from sight. And underwater, it is sonar protection that takes priority.
New invisibility technology will eventually find its way onto the battlefield, but practical solutions are many years away and will be used hand-in-hand with current protection methods for a full range of concealment.