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A cloaking device is an advanced stealth technology that causes an object, such as a spaceship or individual, to be partially or wholly invisible to parts of the electromagnetic (EM) spectrum. Fictional cloaking devices have been used as plot devices in various media for many years, but developments in scientific research show that real-world cloaking devices can obscure objects from at least one wavelength of EM emissions. Scientists already use artificial materials called metamaterials to bend light around an object.[1]
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Conceptual origins
In the fictional Star Trek franchise, cloaking devices were first introduced and used by the Romulans in the original Star Trek episode "Balance of Terror". The invisibility came as a surprise to the crew of the USS Enterprise, who considered it only a theoretical possibility. During a later episode, "The Enterprise Incident", the term "cloaking device" was first coined by writer D.C. Fontana.
Cloaking devices have also been used in many other science-fiction settings and games, including Doctor Who, Star Wars, Stargate, Predator, Halo: Combat Evolved, Metal Gear Solid, and StarCraft. When cloaking devices are used in games, they typically come with a drawback for balance, such as requiring a limited energy source to power them, or failing when the player initiates an attack while cloaked.
Scientific experimentation
An operational, non-fictional cloaking device might be an extension of the basic technologies used by stealth aircraft, such as radar-absorbing dark paint, optical camouflage, cooling the outer surface to minimize electromagnetic emissions (usually infrared), or other techniques to minimize other EM emissions, and to minimize particle emissions from the object. The use of certain devices to jam and confuse remote sensing devices would greatly aid in this process, but are more properly referred to as "active camouflage." Alternatively, metamaterials provide the theoretical possibility of making electromagnetic radiation appear to pass freely through the 'cloaked' object.
Metamaterial research
Optical metamaterials have featured in several recent proposals for invisibility schemes. "Metamaterials" refers to materials that owe their refractive properties to the way they are structured, rather than the substances that compose them. Opals are a well known example of a naturally occurring metamaterial. It has been demonstrated that such materials can take on optical properties unattainable by natural substances. Most famously, a negative refractive index is possible.
Active camouflage
Active camouflage (or adaptive camouflage) is a group of camouflage technologies which would allow an object (usually military in nature) to blend into its surroundings by use of panels or coatings capable of changing color or luminosity. Active camouflage can be seen as having the potential to become the perfection of the art of camouflaging things from visual detection.
Optical camouflage
Optical camouflage is a kind of active camouflage in which one wears a fabric which has an image of the scene directly behind the wearer projected onto it, so that the wearer appears invisible. The concept exists for now only in theory and in proof-of-concept prototypes, although many experts consider it technically feasible. It is an example of active camouflage (or adaptive camouflage). Recently it has been reported that the British Army has tested an invisible tank.[2]
Plasma stealth
Plasma at certain density ranges absorbs certain bandwidths of broadband waves, potentially rendering an object invisible. However, generating plasma in air is too expensive and a feasible alternative is generating plasma between thin membranes instead.[3] The Defense Technical Information Center is also following up research on plasma reducing RCS technologies.[4] IEEE had also looked into the possibility of this device.[5] A plasma cloaking device has been patented in 1991.[6]
See also
References
- ^ Issue 3(on sale through August 2008) of Discovery Channel Magazine, section Going Where No One Has Gone Before, Gary Sledge, Discovery Channel Magazine Issue 3, ISSN 1793572-5
- ^ Ananova - Army tests invisible tank
- ^ Plasma cloaking: Air chemistry, broadband absorption, and plasma generationbackup, February, 1990
- ^ Abstract Electromagnetic-Wave Propagation in Unmagnetized Plasmas, Gregoire, D. J. ; Santoru, J. ; Schumacher, R. W., March, 1992
- ^ A plasma filled tunable notch absorber microwave filter
- ^ John R. Roth "Microwave absorption system" U.S. Patent 4,989,006
- Mosnews Dr Oleg Gadomsky Cloaking Device Article
- MSNBC: Can objects be turned invisible?, detailing the research of Engheta and Alù.
- Optical Camouflage by the Tachi Lab in Japan Optical Camouflage by the Tachi Lab in Japan
- "Experts test cloaking technology". BBC News. 2006-10-19. http://news.bbc.co.uk/1/hi/sci/tech/6064620.stm. Retrieved 2008-08-05. - Thursday 19/10/06
- Space Daily - Engineers Create Optical Cloaking Design For Invisibility - April, 2007
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