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HideWikipedia is getting a new lookHelp us find bugs and complete user interface translations Stealth technologyFrom Wikipedia, the free encyclopediaJump to: navigation, search F-117 stealth attack planeStealth technology also known as LO technology (low observable technology) is a sub-discipline of military tactics and passive electronic countermeasures,[1] which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, in order to make them less visible (ideally invisible) to radar, infrared,[2] sonar and other detection methods.Development in the United States occurred in 1958,[3][4] where earlier attempts in preventing radar tracking of its U-2 spy planes during the Cold War by the Soviet Union had been unsuccessful.[5] Designers turned to develop a particular shape for planes that tended to reduce detection, by redirecting electromagnetic waves from radars.[6] Radar absorbent material was also tested and made to reduce or block radar signals that "bounced" off from the surface of planes. Such changes to shape and surface composition form stealth technology as currently deployed on the B-2 Spirit "Stealth Bomber".[4] Billions of dollars have also been spent in developing stealth over a number of decades but the U.S. has been the only country economically able to do this.[6][7]The concept of stealth is to operate or hide without giving enemy forces any indications as to the presence of friendly forces. This concept was first explored through camouflage by blending into the background visual clutter. As the potency of detection and interception technologies (radar, IRST, surface-to-air missiles etc.) have increased over time, so too has the extent to which the design and operation of military personnel and vehicles have been affected in response. Some military uniforms are treated with chemicals to reduce their infrared signature. A modern "stealth" vehicle will generally have been designed from the outset to have reduced or controlled signature. Varying degrees of stealth can be achieved. The exact level and nature of stealth embodied in a particular design is determined by the prediction of likely threat capabilities.Contents[hide]1 History2 Stealth principles 2.1 Radar cross-section (RCS) reductions 2.1.1 Vehicle shape2.1.2 Non-metallic airframe2.1.3 Radar absorbing material2.1.4 Radar stealth countermeasures and limitations 2.1.4.1 Low frequency radar2.1.4.2 Multiple transmitters2.1.4.3 Moore's law2.2 Acoustics2.3 Visibility2.4 Infrared2.5 Reducing radio frequency (RF) emissions3 Measuring stealth4 Stealth tactics5 List of stealth aircraft 5.1 Manned 5.1.1 Fully stealth designs5.1.2 Reduced RCS designs5.2 Unmanned (full stealth)6 List of stealth ships 6.1 Fully Stealth Designs6.2 Reduced RCS Designs7 See also8 References 8.1 Bibliography8.2 Notes9 External links[edit] HistoryIn England, irregular units of gamekeepers in the 17th century were the first to adopt drab colours (common in the 16th century Irish units) as a form of camouflage, following examples from the continent.Yehudi lights were successfully employed in World War II by RAF Shorts Sunderland aircraft in attacks on U-boats. In 1945 a Grumman Avenger with Yehudi lights got within 3,000?yards (2,700?m) of a ship before being sighted. This ability was rendered obsolete by the radar of the time.One of the earliest stealth aircraft seems to have been the Horten Ho 229 flying wing. This included carbon powder in the glue to absorb radio waves.[8] However, it was never deployed in any quantity.In 1958, the CIA requested funding for a reconnaissance aircraft, to replace U-2 spy planes[9] in which Lockheed secured contractual rights to produce the aircraft.[3]. "Kelly" Johnson and his team at Lockheed's Skunk Works were assigned to produce the A-12 or OXCART the first of the former top secret classified Blackbird series which operated at high altitude of 70000 to 80000?ft and speed of Mach 3.2 to avoid radar detection. Radar absorbent material had already been introduced on U-2 spy planes, and various plane shapes had been developed in earlier prototypes named A1 to A11 to reduce its detection from radar.[4] Later in 1964, using previous models an optimal plane shape taking into account compactness was developed where another "Blackbird", the SR-71, was produced, surpassing previous models in both altitude of 90 000?ft and speed of Mach 3.3.[4]During 1970s, the U.S. Department of Defence then launched a project called Have Blue the project to develop a stealth fighter. Bidding between both Lockheed and Northrop for the tender was fierce to secure the multi billion dollar contract. Lockheed incorporated in its program paper written by a Soviet/Russian physicist Pyotr Ufimtsev in 1962 titled Method of Edge Waves in the Physical Theory of Diffraction, Soviet Radio, Moscow, 1962. In 1971 this book was translated into English with the same title by U.S. Air Force, Foreign Technology Division (National Air Intelligence Center ), Wright-Patterson AFB, OH, 1971. Technical Report AD 733203, Defense Technical Information Center of USA, Cameron Station, Alexandria, VA, 22304-6145, USA. This theory played a critical role in the design of American stealth-aircraft F-117 and B-2.[10][11][12] The paper was able to find whether a plane's shape design would minimise its detection by radar or its radar cross-section (RCS) using a series of equations[13] could be used to evaluate the radar cross section of any shape. Lockheed used it to design a shape they called the Hopeless Diamond, securing contractual rights to mass produce the F-117 Nighthawk.The F-117 project began with a model called "The Hopeless Diamond" (a wordplay on the Hope Diamond) in 1975 due to its bizarre appearance. In 1977 Lockheed produced two 60% scale models under the Have Blue contract. The Have Blue program was a stealth technology demonstrator that lasted from 1976 to 1979. The success of Have Blue lead the Air Force to create the Senior Trend HYPERLINK "" \l "cite_note-13" [14][15] program which developed the F-117.[edit] Stealth principlesThis section needs additional citations for verification.Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2009)Stealth technology (or LO for "low observability") is not a single technology. It is a combination of technologies that attempt to greatly reduce the distances at which a person or vehicle can be detected; in particular radar cross section reductions, but also acoustic, thermal, and other aspects:[edit] Radar cross-section (RCS) reductionsMain article: Radar cross sectionAlmost since the invention of radar, various techniques have been tried to minimize detection. Rapid development of radar during WWII led to equally rapid development of numerous counter radar measures during the period; a notable example of this was the use of chaff.The term "stealth" in reference to reduced radar signature aircraft became popular during the late eighties when the Lockheed Martin F-117 stealth fighter became widely known. The first large scale (and public) use of the F-117 was during the Gulf War in 1991. However, F-117A stealth fighters were used for the first time in combat during Operation Just Cause, the United States invasion of Panama in 1989.[16] Increased awareness of stealth vehicles and the technologies behind them is prompting the development of techniques for detecting stealth vehicles, such as passive radar arrays and low-frequency radars. Many countries nevertheless continue to develop low-RCS vehicles because they offer advantages in detection range reduction and amplify the effectiveness of on-board systems against active radar guidance threats.[ HYPERLINK "" \o "Wikipedia:Citation needed" citation needed][edit] Vehicle shapeThe F-35 Lightning II offers better stealthy features (such as this landing gear door) than previous American fighters, such as the F-16 Fighting FalconThe possibility of designing aircraft in such a manner as to reduce their radar cross-section was recognized in the late 1930s, when the first radar tracking systems were employed, and it has been known since at least the 1960s that aircraft shape makes a significant difference in detectability. The Avro Vulcan, a British bomber of the 1960s, had a remarkably small appearance on radar despite its large size, and occasionally disappeared from radar screens entirely. It is now known that it had a fortuitously stealthy shape apart from the vertical element of the tail. On the other hand, the Tupolev 95 Russian long range bomber (NATO reporting name 'Bear') appeared especially well on radar. It is now known that propellers and jet turbine blades produce a bright radar image; the Bear had four pairs of large (5.6 meter diameter) contra-rotating propellers.Another important factor is the internal construction. Behind the skin of some aircraft are structures known as re-entrant triangles. Radar waves penetrating the skin of the aircraft get trapped in these structures, bouncing off the internal faces and losing energy. This approach was first used on the F-117.The most efficient way to reflect radar waves back to the transmitting radar is with orthogonal metal plates, forming a corner reflector consisting of either a dihedral (two plates) or a trihedral (three orthogonal plates). This configuration occurs in the tail of a conventional aircraft, where the vertical and horizontal components of the tail are set at right angles. Stealth aircraft such as the F-117 use a different arrangement, tilting the tail surfaces to reduce corner reflections formed between them. A more radical approach is to eliminate the tail completely, as in the B-2 Spirit.In addition to altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an existing aircraft, install baffles in the air intakes, so that the turbine blades are not visible to radar. A stealthy shape must be devoid of complex bumps or protrusions of any kind; meaning that weapons, fuel tanks, and other stores must not be carried externally. Any stealthy vehicle becomes un-stealthy when a door or hatch is opened.Planform alignment is also often used in stealth designs. Planform alignment involves using a small number of surface orientations in the shape of the structure. For example, on the F-22A Raptor, the leading edges of the wing and the tail surfaces are set at the same angle. Careful inspection shows that many small structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. The effect of planform alignment is to return a radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles.Stealth airframes sometimes display distinctive serrations on some exposed edges, such as the engine ports. The YF-23 has such serrations on the exhaust ports. This is another example in the use of re-entrant triangles and planform alignment, this time on the external airframe.Shaping requirements have strong negative influence on the aircraft's aerodynamic properties. The F-117 has poor aerodynamics, is inherently unstable, and cannot be flown without a fly-by-wire control system.The stealth ship, K32 HMS HelsingborgShips have also adopted similar techniques. The Visby corvette was the first stealth ship to enter service, though the earlier Arleigh Burke class destroyer incorporated some signature-reduction features [1]. Other examples are the French La Fayette class frigate, the USS San Antonio amphibious transport dock, and most modern warship designs.Similarly, coating the cockpit canopy with a thin film transparent conductor (vapor-deposited gold or indium tin oxide) helps to reduce the aircraft's radar profile, because radar waves would normally enter the cockpit, bounce off an object (the inside of the cockpit has a complex shape, with the pilot's helmet itself providing a sizeable return), and possibly return to the radar, but the conductive coating creates a controlled shape that deflects the incoming radar waves away from the radar. The coating is thin enough that it has no adverse effect on the pilot's vision.[edit] Non-metallic airframeDielectric composites are more transparent to radar, whereas electrically conductive materials such as metals and carbon fibers reflect electromagnetic energy incident on the material's surface. Composites may also contain ferrites to optimize the dielectric and magnetic properties of the material for its application.[edit] Radar absorbing materialMain article: Radar absorbent materialRadar absorbent material (RAM), often as paints, are used especially on the edges of metal surfaces. While the material and thickness of RAM coatings is classified, the material seeks to absorb radiated energy from a ground or air based radar station into the coating and convert it to heat rather than reflect it back.[edit] Radar stealth countermeasures and limitations[edit] Low frequency radarShaping does not offer stealth advantages against low-frequency radar. If the radar wavelength is roughly twice the size of the target, a half-wave resonance effect can still generate a significant return. However, low-frequency radar is limited by lack of available frequencies-many are heavily used by other systems, by lack of accuracy of the diffraction-limited systems given their long wavelengths, and by the radar's size, making it difficult to transport. A long-wave radar may detect a target and roughly locate it, but not identify it, and the location information lacks sufficient weapon targeting accuracy. Noise poses another problem, but that can be efficiently addressed using modern computer technology; Chinese "Nantsin" radar and many older Soviet-made long-range radars were modified this way. It has been said that "there's nothing invisible in the radar frequency range below 2 GHz". [2][edit] Multiple transmittersMuch of the stealth comes from reflecting the transmissions in a different direction other than a direct return. Therefore detection can be better achieved if the sources are spaced from the receivers, known as bistatic radar, and proposals exist to use reflections from sources such as civilian radio transmitters, including cellular telephone radio towers.[17][edit] Moore's lawBy Moore's law the processing power behind radar systems is expected to improve over time, which will erode the ability of physical stealth to hide an aircraft, but that same level of improvement will boost the stealth aircraft's own electronic warfare equipment, which will always have a quieter return signal to mask than a non-stealth aircraft would return.[18][19][edit] AcousticsAcoustic stealth plays a primary role in submarine stealth as well as for ground vehicles. Submarines have extensive usage of rubber mountings to isolate and avoid mechanical noises that could reveal locations to underwater passive sonar arrays.Early stealth observation aircraft used slow-turning propellers to avoid being heard by enemy troops below. Stealth aircraft that stay subsonic can avoid being tracked by sonic boom. The presence of supersonic and jet-powered stealth aircraft such as the SR-71 Blackbird indicates that acoustic signature is not always a major driver in aircraft design, although the Blackbird relied more on its extremely high speed and altitude.[edit] VisibilityThe simplest stealth technology is simply camouflage; the use of paint or other materials to color and break up the lines of the vehicle or person.Most stealth aircraft use matte paint and dark colors, and operate only at night. Lately, interest on daylight Stealth (especially by the USAF) has emphasized the use of gray paint in disruptive schemes, and it is assumed that Yehudi lights could be used in the future to mask shadows in the airframe (in daylight, against the clear background of the sky, dark tones are easier to detect than light ones) or as a sort of active camouflage. The original B-2 design had wing tanks for a contrail-inhibiting chemical, alleged by some to be chlorofluorosulphonic acid[3], but this was replaced in the final design with a contrail sensor from Ophir that alerts the pilot when he should change altitude[20] and mission planning also considers altitudes where the probability of their formation is minimized.[edit] InfraredAn exhaust plume contributes a significant infrared signature. One means of reducing the IR signature is to have a non-circular tail pipe (a slit shape) in order to minimize the exhaust cross-sectional volume and maximize the mixing of the hot exhaust with cool ambient air. Often, cool air is deliberately injected into the exhaust flow to boost this process. Sometimes, the jet exhaust is vented above the wing surface in order to shield it from observers below, as in the B-2 Spirit, and the unstealthy A-10 Thunderbolt II. To achieve infrared stealth, the exhaust gas is cooled to the temperatures where the brightest wavelengths it radiates on are absorbed by atmospheric carbon dioxide and water vapor, dramatically reducing the infrared visibility of the exhaust plume. [4] Another way to reduce the exhaust temperature is to circulate coolant fluids such as fuel inside the exhaust pipe, where the fuel tanks serve as heat sinks cooled by the flow of air along the wings.Ground combat includes the use of both active and passive infrared sensors and so the USMC ground combat uniform requirements document specifies infrared reflective quality standards.[21][edit] Reducing radio frequency (RF) emissionsIn addition to reducing infrared and acoustic emissions, a stealth vehicle must avoid radiating any other detectable energy, such as from onboard radars, communications systems, or RF leakage from electronics enclosures. The F-117 uses passive infrared and low light level television sensor systems to aim its weapons and the F-22 Raptor has an advanced LPI radar which can illuminate enemy aircraft without triggering a radar warning receiver response.[edit] Measuring stealthThe size of a target's image on radar is measured by the radar cross section or RCS, often represented by the symbol σ and expressed in square meters. This does not equal geometric area. A perfectly conducting sphere of projected cross sectional area 1 m2 (i.e. a diameter of 1.13 m) will have an RCS of 1 m2. Note that for radar wavelengths much less than the diameter of the sphere, RCS is independent of frequency. Conversely, a square flat plate of area 1 m2 will have an RCS of σ = 4π A2 / λ2 (where A=area, λ=wavelength), or 13,982 m2 at 10?GHz if the radar is perpendicular to the flat surface.[22] At off-normal incident angles, energy is reflected away from the receiver, reducing the RCS. Modern stealth aircraft are said to have an RCS comparable with small birds or large insects, though this varies widely depending on aircraft and radar.[ HYPERLINK "" \o "Wikipedia:Citation needed" citation needed]If the RCS was directly related to the target's cross-sectional area, the only way to reduce it would be to make the physical profile smaller. Rather, by reflecting much of the radiation away or absorbing it altogether, the target achieves a smaller radar cross section.[5][edit] Stealth tacticsStealthy strike aircraft such as the F-117, designed by Lockheed Martin's famous Skunk Works, are usually used against heavily defended enemy sites such as Command and Control centers or surface-to-air missile (SAM) batteries. Enemy radar will cover the airspace around these sites with overlapping coverage, making undetected entry by conventional aircraft nearly impossible. Stealthy aircraft can also be detected, but only at short ranges around the radars, so that for a stealthy aircraft there are substantial gaps in the radar coverage. Thus a stealthy aircraft flying an appropriate route can remain undetected by radar. Many ground-based radars exploit Doppler filter to improve sensitivity to objects having a radial velocity component with respect to the radar. Mission planners use their knowledge of the enemy radar locations and the RCS pattern of the aircraft to design a flight path that minimizes radial speed while presenting the lowest-RCS aspects of the aircraft to the threat radar. In order to be able to fly these "safe" routes, it is necessary to understand the enemy's radar coverage (see Electronic Intelligence). Airborne or mobile radar systems such as AWACS can complicate tactical strategy for stealth operation.[edit] List of stealth aircraft[edit] Manned[edit] Fully stealth designsRetiredF-117 Nighthawk - Lockheed Martin; retiredIn serviceB-2 Spirit - Northrop GrummanF-22 Raptor - Lockheed Martin / BoeingUnder developmentF-35 Lightning II (JSF) - Lockheed Martin / BAE Systems / Northrop GrummanSukhoi/HAL FGFA - Hindustan Aeronautics LimitedMedium Combat Aircraft - Hindustan Aeronautics LimitedShenyang J-XX - Shenyang Aircraft CorporationMitsubishi ATD-X - Mitsubishi Heavy IndustriesCancelledAtlas Carver - Atlas Aircraft CorporationA-12 Avenger II - McDonnell-Douglas / General DynamicsBoeing X-32 - Boeing - lost to Lockheed for JSFYF-23 Black Widow II - Northrop / McDonnell Douglas - prototype built, but lost competition to YF-22MBB Lampyridae - West German stealth fighter prototypeTechnology demonstratorsBAE Replica - BAE SystemsBoeing Bird of Prey - BoeingHave Blue - LockheedNorthrop Tacit Blue - NorthropNorthrop YB-49[edit] Reduced RCS designsSR-71 Blackbird - Skunkworks Blackbirds were first production RCS aircraft; 1962 with CIA A-12, then later with SR-71, YF-12 and M-21 Blackbird series of aircraftAvro Vulcan - British strategic bomber with delta wing and buried engines that gave an unplanned low radar cross-sectionB-1B LancerDassault Rafale - French Air ForceDe Havilland Mosquito - British light bomber and ground attack plane of wooden construction, low RCS against early radars.Eurofighter TyphoonF-16 Fighting Falcon C/D and E/F - from Block 30 has got reduced RCS to about 1 m2F/A-18 Hornet C/D - reduced RCS, believed be to similar to F-16C'sF/A-18E/F Super Hornet - reduced RCS, believed to have advanced technologyMiG 1.44 - cancelled Russian 5th generation fighterSukhoi Su-47 - Russian technology demonstratorSukhoi PAK FA - Sukhoi (Current T-50 prototype is not stealthy, final design not revealed.)Shenyang J-11B 'Flanker' -RCS reduced to F-16, from original Su-27.Messerschmitt Me 163B rocket-powered fighter aircraft.PZL-230 Skorpion[edit] Unmanned (full stealth)Boeing X-45 - Boeing - based on the manned Boeing Bird of Prey demonstrator (technology demonstrator)[citation needed]BAE Taranis - BAE Systems (UCAV Technology Demonstrator)[citation needed]Dassault nEUROn - (technology demonstrator)[citation needed]EADS Barracuda - EADS of Germany (technology demonstrator)MiG Skat - Mikoyan of Russia (UCAV technology demonstrator)Rheinmetall KZO - Rheinmetall (tactical UAV)RQ-3 DarkStar - Lockheed / Skunk Works (cancelled)[edit] List of stealth ships[edit] Fully Stealth DesignsBraunschweig class corvetteDe Zeven Provinci?n class frigateFuture Dutch Navy offshore patrol vesselsRotterdam class amphibious transport dockF125 class frigateType 45 destroyerFormidable class frigateHamina class missile boatKolkata Class DestroyerKedah class New Generation Patrol VesselsLa Fayette class frigateLittoral combat shipProject 17A class frigateSachsen class frigateSea Shadow (IX-529)Shivalik class frigateSkjold class patrol boatVisby class corvetteType 052C destroyerType 054A frigateZumwalt class destroyerHoubei class missile boatMilgems[edit] Reduced RCS DesignsGerald R. Ford class aircraft carrierArleigh Burke class destroyerSan Antonio class amphibious transport dock[edit] See alsoPyotr Ufimtsev Soviet/Russian physicist who created much of the original theory behind radar stealthPlasma stealthRadarNegative index metamaterials[edit] References^ Rao, G.A., & Mahulikar, S.P., (2002) Integrated review of stealth technology and its role in airpower, Aeronautical Journal, v. 106(1066): 629-641.^ Mahulikar, S.P., Sonawane, H.R., & Rao, G.A., (2007) Infrared signature studies of aerospace vehicles, Progress in Aerospace Sciences, v. 43(7-8): 218-245.^ a b Richelson, J.T. (10 September 2001). "Science, Technology and the CIA". The National Security Archive. The George Washington University. . Retrieved 6 October 2009.?^ a b c d Merlin, P.W. "Design and Development of the Blackbird: Challenges and Lessons Learned" American Institute of Aeronautics and Astronautics 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition 5–8 January 2009, Orlando, Florida. Accessed 2009-10-06.^ Cadirci, S. "RF Stealth (Or Low Observable) and Counter- RF Stealth Technologies: Implications of Counter- RF Stealth Solutions for Turkish Air Force." Naval Postgraduate School, Monterey California, Ph.D. Thesis. March 2009. Accessed 6 October 2009.^ a b Yue, T. (30 November 2001). "Detection of the B-2 Stealth Bomber and a Brief History on “Stealth”". The Tech - Online Edition. Massachusetts Institute of Technology. . Retrieved 5 October 2009.?^ "Military Airplanes". Hawkeye Engineer. College of Engineering, University of Iowa. Fall 2001. . Retrieved 5 October 2009.?^ Myhra 2009, p. 11.^ Poteat, Gene (1998). "Stealth, Countermeasures, and ELINT, 1960-1975". Studies in Intelligence 48 (1): 51–59. .?^ Browne, M.W. "Two rival designers led the way to stealthy warplanes", New York Times, Sci. Times Sec., May 14, 1991.^ Browne, M.W. "Lockheed credits Soviet theory in design of F-117", Aviation Week Space Technology p. 27, December 1991.^ Rich, Ben and L. Janos, Skunk Works, Little Brown, Boston, 1994.^ Knott, E.F; Shaeffer, J.F. & Tuley, M.T. (2004). Radar cross section - Second Edition. Raleigh, North Carolina: SciTech Publishing. pp.?209–214. ISBN?1-891121-25-1. . Retrieved 7 October 2009.?^ F-117A Senior Trend^ "Senior Trend". , 1 April 2008.^ Crocker, H. W. III (2006). Don't Tread on Me. New York: Crown Forum. p.?382. ISBN?9781400053636.?^ MIT's "The Tech - online edition" article Detection of the B-2 Stealth Bomber And a Brief History on “Stealth” by Tao Yue published November 30, 2001 in (Volume 121 >> Issue 63)^ Global Opposition Movement Challenges JSF^ The Naval Institute guide to world naval weapon systems By Norman Friedman, Introduction page x^ Air and Space mag: Why contrails hang around.^ GAO-10-669R Warfighter Support^ Knott, Eugene; Shaeffer, John, and Tuley, Michael (1993). Radar Cross Section, 2nd ed. Artech House, Inc.. pp.?231. ISBN?0-89006-618-3.?[edit] BibliographyDoucet, Arnaud; Freitas, Nando de; Gordon, Neil (2001) [2001]. Sequential Monte Carlo Methods in Practice. Statistics for Engineering and Information Science (1st ed.). Berlin: Springer-Verlag. ISBN?978-0-387-95146-1. . Retrieved 2009-03-11.?Ufimtsev, Pyotr Ya., "Method of edge waves in the physical theory of diffraction," Moscow, Russia: Izd-vo. Sov. Radio [Soviet Radio Publishing], 1962, pages 1–243.Countering stealthHow "stealth" is achieved on F-117AUnited States Patent No.6,297,762. October 2, 2001. Electronic countermeasures system (Apparatus for detecting the difference in phase between received signals at two spaced antennas and for then retransmitting equal amplitude antiphase signals from the two spaced antennas is disclosed.)[edit] NotesThis section needs additional citations for verification.Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (April 2008)[edit] External linksGrant R , The Radar Game - Understanding Stealth and Aircraft Survivability, Iris Independent ResearchThe Advent, Evolution and New Horizons of United States Stealth AircraftWhat is Stealth Technology?Stealth design used for military aircraft?Stealth SatellitesStealth in strike warfareStealth technologyThe Paradigm Shift in Air Superiority (Stealth)Stealth TechnologyUSAF Stealth Fighters briefingPyotr Ufimstev biographyAdvancement of Plasma antennas in stealthRetrieved from ""Categories: Military technology | Radar | Aerial warfare | Aviation terminologyHidden categories: Articles needing additional references from March 2009 | All articles needing additional references | All articles with unsourced statements | Articles with unsourced statements from June 2009 | Articles with unsourced statements from February 2008 | Articles with unsourced statements from January 2008 | Articles needing additional references from April 2008Personal toolsNew featuresLog in / create accountNamespacesArticleDiscussionVariantsViewsReadEditView historyActionsSearchTop of Form? 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See Terms of Use for details.Wikipedia? is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.Contact usPrivacy policyAbout WikipediaDisclaimersHideWikipedia is getting a new lookHelp us find bugs and complete user interface translations Plasma stealthFrom Wikipedia, the free encyclopediaJump to: navigation, search Plasma stealth is a proposed process that uses ionized gas (plasma) to reduce the radar cross section (RCS) of an aircraft. Interactions between electromagnetic radiation and ionized gas have been extensively studied for a variety of purposes, including the possible concealment of aircraft from radar that plasma stealth theorizes. While it is theoretically possible to reduce an aircraft's RCS by wrapping the airframe in plasma, it may be very difficult to do so in practice. Various methods might plausibly be able to produce a layer or cloud of plasma around an airframe, from "simple" electrostatic or RF discharges to more exotic possibilities like laser-produced plasmas [1].Contents[hide]1 First claims2 Plasma and its properties3 Plasmas on aerodynamic surfaces4 Absorption of EM radiation5 Theoretical work with Sputnik6 Footnotes7 See also[edit] First claimsIn 1956, Arnold Eldredge, of General Electric, filed a patent application for an "Object Camouflage Method and Apparatus," which proposed using a particle accelerator in an aircraft to create a cloud of ionization that would "...refract or absorb incident radar beams." It is not known who funded this work or whether it was prototyped and tested. U.S. Patent 3,127,608 was granted in 1964.[2]During Project OXCART, the operation of the Lockheed A-12 reconnaissance aircraft, the CIA funded an attempt to reduce the RCS of the A-12's inlets. Known as Project KEMPSTER, this used an electron beam generator to create a cloud of ionization in front of each inlet. The system was flight tested but was never deployed on operational A-12s or SR-71s.[3]Despite the apparent technical difficulty of designing a plasma stealth device for combat aircraft, there are claims that a system was offered for export by Russia in 1999. In January 1999, the Russian ITAR-TASS news agency published an interview with Doctor Anatoliy Koroteyev, the director of the Keldysh Research Center (FKA Scientific Research Institute for Thermal Processes), who talked about the plasma stealth device developed by his organization. The claim was particularly interesting in light of the solid scientific reputation of Dr. Koroteyev and the Institute for Thermal Processes[ HYPERLINK "" \o "Wikipedia:Citation needed" citation needed], which is one of the top scientific research organizations in the world in the field of fundamental physics.[4]The Journal of Electronic Defense reported that "plasma-cloud-generation technology for stealth applications" developed in Russia reduces an aircraft's RCS by a factor of 100. According to this June 2002 article, the Russian plasma stealth device has been tested aboard a Sukhoi Su-27IB fighter-bomber. The Journal also reported that similar research into applications of plasma for RCS reduction is being carried out by Accurate Automation Corporation (Chattanooga, Tennessee) and Old Dominion University (Norfolk, Virginia) in the U.S.; and by Dassault Aviation (Saint-Cloud, France) and Thales (Paris, France).[5][edit] Plasma and its propertiesMain article: Plasma (physics)A plasma is a quasineutral (total electrical charge is close to zero) mix of ions (atoms which have been ionized, and therefore possess a net charge), electrons, and neutral particles (possibly including un-ionized atoms). Not all plasmas are fully ionized. Almost all the matter in the universe is plasma: solids, liquids and gases are uncommon away from planetary bodies. Plasmas have many technological applications, from fluorescent lighting to plasma processing for semiconductor manufacture.Plasmas can interact strongly with electromagnetic radiation: this is why plasmas might plausibly be used to modify an object's radar signature. Interaction between plasma and electromagnetic radiation is strongly dependent on the physical properties and parameters of the plasma, most notably, the temperature and density of the plasma. Plasmas can have a wide range of values in both temperature and density; plasma temperatures range from close to absolute zero and to well beyond 109 kelvins (for comparison, tungsten melts at 3700 kelvins), and plasma may contain less than one particle per cubic metre, or be denser than lead. For a wide range of parameters and frequencies, plasma is electrically conductive, and its response to low-frequency electromagnetic waves is similar to that of a metal: a plasma simply reflects incident low-frequency radiation. The use of plasmas to control the reflected electromagnetic radiation from an object (Plasma stealth) is feasible at higher frequency where the conductivity of the plasma allows it to interact strongly with the incoming radio wave, but the wave can be absorbed and converted into thermal energy rather than reflected.Plasmas support a wide range of waves, but for unmagnetised plasmas, the most relevant are the Langmuir waves, corresponding to a dynamic compression of the electrons. For magnetised plasmas, many different wave modes can be excited which might interact with radiation at radar frequencies.[edit] Plasmas on aerodynamic surfacesPlasma layers around aircraft have been considered for purposes other than stealth. There are many research papers on the use of plasma to reduce aerodynamic drag. In particular, electrohydrodynamic coupling can be used to accelerate air flow near an aerodynamic surface. One paper HYPERLINK "" \l "cite_note-drag-5" [6] considers the use of a plasma panel for boundary layer control on a wing in a low-speed wind tunnel. This demonstrates that it is possible to produce a plasma on the skin of an aircraft. Xenon nuclear poison isotopes when successfully suspended in the plasma layers or vehicle hull can be utilized to reduce radar cross-section and will shield against HMP/EMP and HERF weaponry.[edit] Absorption of EM radiationWhen electromagnetic waves, such as radar signals, propagate into a conductive plasma, ions and electrons are displaced as a result of the time varying electric and magnetic fields. The wave field gives energy to the particles. The particles generally return some fraction of the energy they have gained to the wave, but some energy may be permanently absorbed as heat by processes like scattering or resonant acceleration, or transferred into other wave types by mode conversion or nonlinear effects. A plasma can, at least in principle, absorb all the energy in an incoming wave, and this is the key to plasma stealth. However, plasma stealth implies a substantial reduction of an aircraft's RCS, making it more difficult (but not necessarily impossible) to detect. The mere fact of detection of an aircraft by a radar does not guarantee an accurate targeting solution needed to intercept the aircraft or to engage it with missiles. A reduction in RCS also results in a proportional reduction in detection range, allowing an aircraft to get closer to the radar before being detected.The central issue here is frequency of the incoming signal. A plasma will simply reflect radio waves below a certain frequency (which depends on the plasma properties). This aids long-range communications, because low-frequency radio signals bounce between the Earth and the ionosphere and may therefore travel long distances. Early-warning over-the-horizon radars utilize such low-frequency radio waves. Most military airborne and air defense radars, however, operate in the microwave band, where many plasmas, including the ionosphere, absorb or transmit the radiation (the use of microwave communication between the ground and communication satellites demonstrates that at least some frequencies can penetrate the ionosphere). Plasma surrounding an aircraft might be able to absorb incoming radiation, and therefore prevent any signal reflection from the metal parts of the aircraft: the aircraft would then be effectively invisible to radar. A plasma might also be used to modify the reflected waves to confuse the opponent's radar system: for example, frequency-shifting the reflected radiation would frustrate Doppler filtering and might make the reflected radiation more difficult to distinguish from noise.Control of plasma properties is likely to be important for a functioning plasma stealth device, and it may be necessary to dynamically adjust the plasma density, temperature or composition, or the magnetic field, in order to effectively defeat different types of radar systems. Radars which can flexibly change their transmission frequency might be less susceptible to defeat by plasma stealth technology. Like LO geometry and radar absorbent materials, plasma stealth technology is probably not a panacea against radar.Plasma stealth technology also faces various technical problems. For example, the plasma itself emits EM radiation. Also, it takes some time for plasma to be re-absorbed by the atmosphere and a trail of ionized air would be created behind the moving aircraft. Thirdly, plasmas (like glow discharges or fluorescent lights) tend to emit a visible glow: this is not necessarily compatible with overall low observability. Furthermore, it is likely to be difficult to produce a radar-absorbent plasma around an entire aircraft traveling at high speed. However, a substantial reduction of an aircraft's RCS may be achieved by generating radar-absorbent plasma around the most reflective surfaces of the aircraft, such as the turbojet engine fan blades, engine air intakes, and vertical stabilizers.[edit] Theoretical work with SputnikDue to the obvious military applications of the subject, there are few readily available experimental studies of plasma's effect on the radar cross section (RCS) of aircraft, but plasma interaction with microwaves is a well explored area of general plasma physics. Standard plasma physics reference texts are a good starting point and usually spend some time discussing wave propagation in plasmas.One of the most interesting articles related to the effect of plasma on the RCS of aircraft was published in 1963 by the IEEE. The article is entitled "Radar cross sections of dielectric or plasma coated conducting spheres and circular cylinders" (IEEE Transactions on Antennas and Propagation, September 1963, pp.?558–569). Six years earlier—in 1957—the Soviets had launched the first artificial satellite. While trying to track Sputnik it was noticed that its electromagnetic scattering properties were different from what was expected for a conductive sphere. This was due to the satellite's traveling inside of a plasma shell: the ionosphere.The Sputnik's simple shape serves as an ideal illustration of plasma's effect on the RCS of an aircraft. Naturally, an aircraft would have a far more elaborate shape and be made of a greater variety of materials, but the basic effect should remain the same. In the case of the Sputnik flying through the ionosphere at high velocity and surrounded by a naturally-occurring plasma shell, there are two separate radar reflections: the first from the conductive surface of the satellite itself and the second from the dielectric plasma shell.The authors of the paper found that a dielectric (plasma) shell may either decrease or increase the echo area of the object. If either one of the two reflections is considerably greater, then the weaker reflection will not contribute much to the overall effect. The authors also stated that the EM signal that penetrates the plasma shell and reflects off the object's surface will drop in intensity while traveling through plasma, as was explained in the previous section.The most interesting effect is observed when the two reflections are of the same order of magnitude. In this situation the two components (the two reflections) will be added as phasors and the resulting field will determine the overall RCS. When these two components are out of phase relative to each other, cancellation occurs. This means that under such circumstances the RCS becomes null and the object is completely invisible to the radar.It is immediately apparent that performing similar numeric approximations for the complex shape of an aircraft would be difficult. This would require a large body of experimental data for the specific airframe, properties of plasma, aerodynamic aspects, incident radiation, etc. On the other hand, the original computations discussed in this paper were done by a handful of people on an IBM 704 computer made in 1956, and at the time, this was a novel subject with very little research background. So much has changed in science and engineering since 1963 that differences between a metal sphere and a modern combat jet pale in comparison.A simple application of plasma stealth is the use of plasma as an antenna: metal antenna masts often have large radar cross sections, but a hollow glass tube filled with low pressure plasma can also be used as an antenna, and is entirely transparent to radar when not in use.[edit] Footnotes^ I.V. Adamovich, J. W. Rich, A.P. Chernukho, and S.A. Zhdanok (2000). "Analysis of the Power Budget and Stability of High-Pressure Nonequilibrium Air Plasmas". Proceedings of 31st AIAA Plasmadynamics and Lasers Conference, June 19–22,2000. pp.?Paper 00-2418. .?^ Eldredge, Arnold, "Object Camouflage Method and Apparatus", US patent 3127608, published Aug. 6, 1956, issued Mar. 31, 1964?^ The U-2's Intended Successor: Project Oxcart 1956-1968, approved for release by the CIA in October 1994. Retrieved: 26 January 2007.^ Nikolay Novichkov.Russian scientists created revolutionary technologies for reducing radar visibility of aircraft. "ITAR-TASS", January 20, 1999.^ Fiszer, Michal and Jerzy Gruszczynski. "Russia Working on Stealth Plasma". Journal of Electronic Defense, June 2002.^ J. Reece Roth (2003). "Aerodynamic flow acceleration using paraelectric and peristaltic electrohydrodynamic ?(EHD) effects of a One Atmosphere Uniform Glow Discharge Plasma ?(OAUGDP)'". Physics of Plasmas 10: 2127–2135.?[edit] See alsoStealth technologyRetrieved from ""Categories: Radar | Plasma physicsHidden categories: All articles with unsourced statements | Articles with unsourced statements from April 2010Personal toolsNew featuresLog in / create accountNamespacesArticleDiscussionVariantsViewsReadEditView historyActionsSearchTop of Form? SearchBottom of FormNavigationMain pageContentsFeatured contentCurrent eventsRandom articleInteractionAbout WikipediaCommunity portalRecent changesContact WikipediaDonate to WikipediaHelpToolboxWhat links hereRelated changesUpload fileSpecial pagesPermanent linkCite this pagePrint/exportCreate a bookDownload as PDFPrintable versionLanguages???????Fran?aisThis page was last modified on 19 June 2010 at 13:02.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of Use for details.Wikipedia? is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.Contact usPrivacy policyAbout WikipediaDisclaimersFirst developed by the Russians, plasma stealth technology is also known as “Active Stealth Technology”. Plasma stealth is a proposed process that uses ionized gas (plasma) to reduce the radar cross section (RCS) of an aircraft. A plasma stream is injected in front of the aircraft covering the entire body of the aircraft and absorbing most of the electromagnetic energy of the radar waves, thus making the aircraft difficult to detect.There are few experimental studies of plasma’s effect on RCS. One of the most interesting articles was published by the Institute of Electrical and Electronics Engineers (IEEE) in 1963 and described the effect of plasma on the RCS of aircraft. The article entitled “Radar cross sections of dielectric or plasma coated conducting spheres and circular cylinders” was based on the data offered by Sputnik, the first artificial satellite launched by the Soviet Union on October 4, 1957. While trying to track Sputnik it was noticed that its electromagnetic scattering properties were different from what was expected for a conductive sphere. This was due to the satellite traveling inside of a plasma shell.While Sputnik was flying at high velocity through the ionosphere it was surrounded by a naturally-occuring plasma shell and because of it there were two separate radar reflections: the first from the surface of the satellite itself and the second from the plasma shell. If one of the reflections is greater the other one will not contribute much to the overall effect. When the two reflections have the same order of magnitude and are out of phase relative to each other cancellation occurs and the RCS becomes null. The aircraft becomes invisible to radar.In January 1999, the Russian news agency ITAR-TASS published an interview with Doctor Anatoliy Koroteyev who talked about the plasma stealth device developed by his organization. Doctor Koroteyev was the director of the Keldysh Research Center. There have also been claims that in 2002 the Russians tested a plasma stealth device on board a Su-27 and RCS was reduced by a factor of 100.The Keldysh Research Center has created a plasma generator that weights no more than 100 kilos, thus making it possible to be fitted on board most tactical aircraft. Current stealth technology uses radar absorbent materials (RAM) and angled surfaces that don’t reflect radar waves back. This constitutes as a main drawback, since an alteration of the airframe has negative effects on the flight characteristics of these aircraft. The third generation stealth technology F-22 Raptor seems however to be an exception since it is both a fast aicraft and very maneuverable.By using a plasma generator the aerodynamic characteristics of the aircraft do not suffer which in term means that the payload is increased making it more effective. The use of this technology offers the benefit of not having to carry the payload internally to be able to fool enemy radar. The Sukhoi Su-35 and the MiG-35 (both upgrades of Su-27 and MiG-29) are the first to benefit from this technology.One of the most interesting russian fighters to benefit from the plasma stealth technology is the MiG 1.42/1.44 also known as the MFI (Mnogofunktsionalny Frontovoi Istrebitel - Multifunctional Frontline Fighter). This new aircraft is a fifth generation air-superiority fighter, a rival for the american F-22 Raptor. Both aircraft have the same supercruise capability as well as thrust vectoring for supermaneuverability (a capability to fly at supercritical angles of attack, at increased level of sustained andavailable g-loads and high turn-angle rate, which require a greater thrust-to-weight ratio and improved wing aerodynamic efficiency). This aircraft may prove to be a milestone in aviation, as so many russian aircraft were before.Stealth Technology for Future WarshipsBAE Systems has unveiled a technology mast demonstrator designed for future warships, required to meet increasingly complex operational demands. The mast is a critical component of a modern warship and the technology mast demonstrator has been designed to combine long-range radar, numerous high power sensors and communications antennae and equipment in a way that minimises mutual interference.Other advantages of the mast are that it is light, tall, yet almost invisible (stealthy) to an enemy radar and offers the customer a low maintenance, easy to upgrade solution. The completely integrated unit is an excellent example of the radar, communication, design and shipbuilding skills. This technology has been developed as a private venture by the company, in keeping with the MoD's Smart Procurement approach.The new mast is designed to form a key component of the ship's upper superstructure. It comprises a steel substructure clad in advanced Fibre Reinforced Plastic composite panels, which incorporate radar-absorbing layers. Sensors are installed in interchangeable modules mounted within the cladding. The philosophy of this mast is intended to support future surface warship designs and retrofit to existing ships. ................
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