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Stealth and Anti Stealth Technology

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A Technical Paper Presentation On STEALTH AND ANTI-STEALTH TECHNOLOGY Presented By Ch.Meher Subash (07991A04D2) Department of Electronics and Communication Engineering St.Theressa Institute of Engineering and Technology Garividi.
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Page 1: Stealth and Anti Stealth Technology

A Technical Paper Presentation

On

STEALTH AND ANTI-STEALTH TECHNOLOGY

Presented ByCh.Meher Subash

(07991A04D2)Department of Electronics and Communication Engineering

St.Theressa Institute of Engineering and TechnologyGarividi.

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ABSTRACT

Stealth technology has as its fundamental principle the prevention of detection by the enemy, and applies not only to aircraft as is commonly assumed, but also increasingly to naval vessels and to armored vehicles, although in the latter cases, it is nascent technology upon which comment must be reserved. Stealth technology, therefore, does not simply mean the evasion by aircraft of radar through the reduction of radar signature. It also encompasses the reduction of an aircraft's visibility in other spectra, most notably acoustic, visual, and infra-red. Consequently the popular term ‘stealth technology’ would perhaps be better referred to as ‘low-observable technology’.

Stealth technology provides its users with a number of tactical advantages. As well as allowing the penetration of heavily defended airspace, it enables single aircraft to carry out attacks in a manner impossible for conventional aircraft, which require a large number of support aircraft to conduct similar missions, including escort, defense suppression, and electronic warfare types. A conventional aircraft ‘package’ may employ up to 40 aircraft, while a stealth aircraft can conduct the mission by itself. This naturally requires the use of precision-guided weapons to ensure that the single aircraft has a high probability of success. Stealth is not without its drawbacks. The cost of the technology is enormous, and it is hard to envisage that its eventual employment in maritime and land operations will ever be obtained at a price comparable to conventional technology. Nonetheless, precisely

because of its elevated cost it does emphasize the economic power of the USA as well as its immense advantage in science and technology over the rest of the world.

Topics to be discussed:

History of Stealth TechnologyRADAR StealthAbsorptionDeflectionCounter StealthAnti Stealth TechnologyMethods of Anti Stealth Technology

Airborne methodSatellite Based MethodSurface Based Method

Advantagesconclusion

History of Stealth Technology:

Development of stealth technology for aircraft began before World War I. Because RADAR had not been invented, visibility was the sole concern, and the goal was to create aircraft that were hard to see. In 1912, German designers produced a largely transparent monoplane; its wings and fuselage were covered by a transparent material derived from cellulose, the basis of movie film, rather than the opaque canvas standard in that era. Interior struts and other parts were painted with light colors to further reduce visibility. The plane was effectively invisible from the ground when flow at 900 ft (274 m) or higher, and faintly visible at lower

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altitudes. Several transparent German aircraft saw combat during World War I, and Soviet aircraft designers attempted the design of transparent aircraft in the 1930s.

With the invention of RADAR during World War II, stealth became both more needful and more feasible: more needful because RADAR was highly effective at detecting aircraft, and would soon be adapted to guiding antiaircraft missiles and gunnery at them, yet more feasible because to be RADAR-stealthy an aircraft did need to be not be completely transparent to radio waves; it could absorb or deflect them.

During World War II, Germany coated the snorkels of its submarines with RADAR-absorbent paint to make them less visible to RADAR’s carried by Allied antisubmarine aircraft. In 1945 the U.S. developed a RADAR-absorbent paint containing iron. It was capable of making an airplane less RADAR-reflective, but was heavy; several coats of the material, known as MX-410, could make an aircraft unwieldy or even too heavy to fly. However, stealth development continued throughout the postwar years. In the mid 1960s, the U.S. built a high-altitude reconnaissance aircraft, the Lockheed SR-71 Blackbird, which was extremely RADAR-stealthy for its day. The SR-71 included a number of stealth features, including special RADAR-absorbing structures along the edges of wings and tailfins, a cross-sectional design featuring few vertical surfaces that could reflect RADAR directly back toward a transmitter, and a coating termed "iron ball" that could be electronically manipulated to produce a variable, confusing RADAR reflection. The SR-

71, flying at approximately 100,000 feet, was routinely able to penetrate Soviet airspace without being reliably tracked on RADAR.

RADAR Stealth:

RADAR is the use of reflected electromagnetic waves in the microwave part of the spectrum to detect targets or map landscapes. RADAR first illuminates the target, that is, transmits a radio pulse in its direction. If any of this energy is reflected by the target, some of it may be collected by a receiving antenna. By comparing the delay times for various echoes, information about the geometry of the target can be derived and, if necessary, formed into an image. RADAR stealth or invisibility requires that a craft absorb incident RADAR pulses, actively cancel them by emitting inverse waveforms, deflect them away from receiving antennas, or all of the above. Absorption and deflection, treated below, are the most important prerequisites of RADAR stealth.

Absorption:

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Metallic surfaces reflect RADAR; therefore, stealth aircraft parts must either be coated with RADAR-absorbing materials or made out of them to begin with. The latter is preferable because an aircraft whose parts are intrinsically RADAR-absorbing derives aerodynamic as well as stealth function from them, whereas a RADAR-absorbent coating is, aerodynamically speaking, dead weight. The F-117 stealth aircraft is built mostly out of a RADAR-absorbent material termed Fibaloy, which consists of glass fibers embedded in plastic, and of carbon fibers, which are used mostly for hot spots like leading wing-edges and panels covering the jet engines. Thanks to the use of such materials, the airframe of the F-117 (i.e., the plane minus its electronic gear, weapons, and engines) is only about 10% metal. Both the B-2 stealth bomber and the F-117 reflect about as much RADAR as a hummingbird

Many RADAR-absorbent plastics, carbon-based materials, ceramics, and blends of these materials have been developed for use on stealth aircraft. Combining such materials with RADAR-absorbing surface geometry enhances stealth. For example, wing surfaces can be built on a metallic substrate that is shaped like a field of pyramids with the spaces between the pyramids filled by a RADAR-absorbent material. RADAR waves striking the surface zigzag inward between the pyramid walls, which increases absorption by lengthening signal path through the absorbent material. Another example of structural absorption is the placement of metal screens over the intake vents of jet engines. These screens—used, for example, on the F-117 stealth fighter—absorb RADAR

waves exactly like the metal screens embedded in the doors of microwave ovens. It is important to prevent RADAR waves from entering jet intakes, which can act as resonant cavities (echo chambers) and so produce bright RADAR reflections.

The inherently high cost of RADAR-absorbent, airframe-worthy materials makes stealth aircraft expensive; each B-2 bomber costs approximately $2.2 billion, while each F-117 fighter costs approximately $45 million; the U.S. fields 21 B-2s and 54 F-117s. The Russian Academy of Sciences, however, according to a 1999 report by Jane's Defense Weekly, claims to have developed a low-budget RADAR-stealth technique, namely the cloaking of aircraft in ionized gas (plasma). Plasma absorbs radio waves, so it is theoretically possible to diminish the RADAR reflectivity of an otherwise non-stealthy aircraft by a factor of 100 or more by generating plasma at the nose and leading edges of an aircraft and allowing it flow backward over the fuselage and wings. The Russian system is supposedly lightweight (>220 lb [100 kg]) and retrofit table to existing aircraft, making it the stealth capability available at least cost to virtually any air force. A disadvantage of the plasma technique that it would probably make the aircraft glow in the visible part of the spectrum.

Deflection:

Most Radar are monotonic, that is, for reception they use either the same antenna as for sending or a separate receiving antenna collocated with the sending antenna; deflection therefore means reflecting RADAR pulses in any direction other than the one they came

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from. This in turn requires that stealth aircraft lack flat, vertical surfaces that could act as simple RADAR mirrors. RADAR can also be strongly reflected wherever three planar surfaces meet at a corner. Planes such as the B-52 bomber, which have many flat, vertical surfaces and RADAR-reflecting corners, are notorious for their RADAR-reflecting abilities; stealth aircraft, in contrast, tend to be highly angled and streamlined, presenting no flat surfaces at all to an observer that is not directly above or below them. The B-2 bomber, for example, is shaped like a boomerang.

A design dilemma for stealth aircraft is that they need not only to be invisible to RADAR but to use RADAR; inertial guidance, the Global Positioning System, and laser RADAR can all help aircraft navigate stealthily, but an aircraft needs conventional RADAR to track incoming missiles and hostile aircraft. Yet the transmission of RADAR pulses by a stealth aircraft wishing to avoid RADAR detection is self-contradictory. Furthermore, RADAR and radio antennas are inherently RADAR-reflecting.

A Stealthy Air Craft

Counter-stealth:

An aircraft cannot be made truly invisible. For example, no matter how cool the exhaust vents of an aircraft are kept, the same amount of heat is always liberated by burning a given amount of fuel, and this heat must be left behind the aircraft as a trail of warm air. Infrared-detecting devices might be devised that could image this heat trail as it formed, tracking a stealth aircraft.

Furthermore, every jet aircraft leaves swirls of air—vortices—in its wake. Doppler radar, which can image wind velocities, might pinpoint such disturbances if it could be made sufficiently high-resolution.

Other anti-stealth techniques could include the detection of aircraft-caused disturbances in the Earth's magnetic field (magnetic anomaly detection), networks of low frequency radio links to detect stealth aircraft by interruptions in transmission, the use of specially shaped RADAR pulses that resist absorption, and netted RADAR. Netted RADAR is the use of more than one receiver, and possibly more than one transmitter, in a network. Since stealth aircraft rely partly on deflecting RADAR pulses, receivers located off the line of pulse transmission might be able to detected deflected echoes. By illuminating a target area using multiple transmitters and linking multiple receivers into a coordinated network, it should be possible to greatly increase one's chances of detecting a stealthy target. No single receiver may record a strong or steady echo from any single transmitter, but the network as a whole might collect enough information to track a stealth target.

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ANTI-STEALTH

TECHNOLOGY:Modern military stealth

technology is based on the principle that stealthy craft remain invisible to detecting radar and infrared sensors, especially at long ranges. Such technology can be entirely nullified by the detecting radar and/or infrared sensors searching, not for the stealthy craft itself, but for the background behind the stealthy craft. The stealth craft will then show up in the form of a black or blank silhouette in front of the background. This is much like the way one can pinpoint with extreme accuracy the location of the moon during a solar eclipse, and track its movement with great precision, even though during a solar eclipse one cannot observe the moon itself. (N.B.: The remainder of this document describes the detailed methods one might use to detectthe background behind stealth craft. Thus it is not necessary to read the entire document in order to grasp the principle of Anti-Stealth Technology, though one may of course do so to dispel all skepticism as to its practicability.)

Basic Principles of Modern Stealth Technology: Military stealth technology, such as is used, for example, in the B-2 bomber, the F-117fighter-bomber and the F-22 fighter, and as is intended for the future Comanche helicopter, and the next-generation tank which is intended to replace the current M1A2 Abrams tank — is based on the principle that the stealthy craft remains invisible to detecting radar and infrared sensors, especially at long ranges. With respect to

radar, this is accomplished, in basic principle, by the stealthy craft absorbing almost all the radar waves emanated by detecting radar sources, and/or reflecting or deflecting the detecting radar in direction(s) other than towards the detecting sensors. With respect to infrared, the objective of stealth is achieved, in basic principle, by the stealthy craft minimizing heat from its engines and other heat-emitting spots. As a result of applying the above principles, detecting sensors searching for a stealthy craft cannot detect any radar or infrared signal emanating from the craft, except perhaps at very close distances, when it may already be too late to do anything about it from a military viewpoint. The craft, therefore, cannot be observed by radar or infrared sensors.

1. Airborne MethodOne way to accomplish the above is for the detecting forces to fly a high-flying aircraft furnished with SLAR (Side-Looking Airborne Radar) and/or FLIR (Front-Looking Infra-Red) equipment to map out the terrain below and to one side, or to the front. If a stealth craft were operating anywhere above the terrain being mapped, a small patch of terrain, which the stealth craft would perforce eclipse, would not be observed on the detecting aircraft’s output screen. That particular spot would appear black or blank, and more or less in the shape of a silhouette of the stealth craft: thereby pinpointing the stealth craft’s position within the field of vision of the detecting aircraft. The initial detection of a distant stealth craft might be slow, since until the craft were detected,the equipment would have to scan the entire terrain over which the craft might be located. However, once that location

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were pinpointed, the craft could be tracked much more swiftly and accurately by zooming in on that location and some of its surrounding area, and scanning only that relatively small part of the field of vision. This would enable the searching equipment to generate much more detailed images of the silhouette of the craft in question, perhaps even identifying the craft by that silhouette. If, in addition, the SLAR or FLIR equipment were furnished with rangefinder capability (as many such are), the exact position of the stealth craft in three dimensions could also be determined. This would not greatly matter, of course, if the stealth craft were a land vehicle (like a tank); but in the case of aircraft such data could provide very valuable information from a military point of view. And with modern computers this position could be calculated very swiftly indeed: almost instantaneously.

2. Satellite-Based MethodThe same method may be used looking down on the battlefield from satellites equipped with radar sensors. Although satellites would be relatively far away from the battlefield a couple of hundred miles away, or even more — they would be able to remain out of range of most hostile weapons, and thus would not run much risk of being shot down, as might aircraft. Also, satellites would be able to cover a much larger area of the battlefield, thus being in a position to locate and track virtually all hostile stealth craft.

3. Surface-Based MethodYet another way of detecting a stealth aircraft would be for surface-based radar installations to scan the sky at high apertures and with high sensitivity, such

as is done with radio telescopes. (Since such installations would be surface-based, even if they had to be substantially large and/or heavy to adequately accomplish this task, their size and weight would not be a serious deterrent to their accomplishing it.) As is well known to radio astronomers, even in daytime or in bad weather, radio signals from the stars would reach the radar installations uninterrupted. Since the radio map of the stars is by now very well known, it may be assumed that if any star is not observed on the detecting screen or output device, that particular star must be eclipsed by some craft flying above the installation somewhere along the line of sight between the installation and that particular star. And with very sensitive radio-astronomical equipment, virtually every part of the sky is observed to be covered with stars! Therefore at almost every instant in time, the stealth aircraft would be eclipsing one or another known star. Even if less sensitive detecting equipment were used, so that the time it took to record the stellar images was greater than the time it took for an aircraft to entirely eclipse a particular star, that star would still show up on the detecting screen somewhat fainter than it would otherwise if ithad not been eclipsed by the aircraft for a part of the time it took for the radio waves from it to be gathered. Thus by calibrating the detecting equipment to search for those stars whose radio images appear to be fainter than usual (as determined by standard radio maps of the sky), the position of the eclipsing aircraft could be determined swiftly, even with equipment of less than stellar performance. Indeed the limit of sensitivity of the equipment as a whole would be determined, not by the

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sensitivity of the radio signal gathering device, but by the sensitivity of the equipment which detects the difference in intensity of the actual signals from particular stars compared to their intensity as indicated by the standard radio map of those same stars. And as with the airborne method, although the initial detection of a distant stealth aircraft might be slow, once its location were pinpointed, the aircraft could be tracked much more swiftly and accurately by zooming in on that location and some of surrounding area. If more than one detecting installation were used, by a process of triangulation the exact location in three dimensions of all aircraft — friendly as well as hostile — within the fields of vision of the relevant installations could be determined with great accuracy. And as mentioned earlier, with Modern computers such a determination could be arrived at almost instantaneously.With the passage of time, the specific stars being eclipsed by any particular aircraft would change in a manner consistent with the aircraft’s trajectory. Thus by accurately observing the time intervals between sequentially-eclipsed stars, coupled with an exact knowledge of the radio-astronomical map, the aircraft’s trajectory could easily and quickly — almost instantly — be calculated, especially if powerful computers were utilized to calculate it. If, in addition, the locations of all the friendly aircraft within the field of vision of the installation are also known, it may be assumed that hostile aircraft must be

eclipsing those stars not showing up on the screen which cannot be accounted for by friendly aircraft. Thus by a process of elimination, the location of all hostile aircraft, and not just hostile stealth aircraft, could be determined. This would be an advantage of the surface-based method as opposed to the airborne method described earlier. And, of course, with modern computers all the above calculations could be performed extremely rapidly: almost instantaneously.

Further Advantages of the Surface-Based Method:

One further advantage of the surface-based method, as opposed to the airborne method described earlier, is that the detecting installation(s) need not emit any radio signals themselves. Thus it would be impossible for hostile aircraft to home in on their radio emissions in order to destroy the installations, which add to their safety factor: especially if from a visual point of view these installations were also carefully camouflaged.Another advantage of the surface-based installations would be that they could also be equipped with powerful surface-to-air missiles (SAMs), which could be much larger and possess much greater range and destructive power than air-based missiles for the destruction of hostile stealth aircraft. And since these particular SAMs need not themselves emit any radar signals either, but could

merely fly along a narrow beam (say, a laser beam) emanating from the installation which has detected the stealth aircraft, the latter would get no warning that one or more SAMs have

been launched against it, and thus would not have a chance to take evasive action.

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Conclusion:Both technology and skills goes hand in hand so that those who possess better technology and skills will definitely win the war or detect the missiles or aircrafts. You might think that this technology was related to our department only but it is a core technology related to several disciplines of technology.

ECE, EEE People will develop RADAR,MECHANICAL People will design Aircrafts,CSE, IT people will calculate Throughput and perform analysis,CHEMICAL people will prepare absorbing materials.

Unlikely such new kinds of stealth technology can be developed in so short a time.

……………Be Invisible…………

REFERENCES: WWW.STEALTH.EDU.COM WWW.ANTI-STEALTH.COM


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