Presented By
Ch.Meher Subash

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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 Technology
RADAR Stealth
Absorption
Deflection
Counter Stealth
Anti Stealth Technology
Methods of Anti Stealth Technology
Airborne method
Satellite Based Method
Surface Based Method
Advantages
conclusion
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 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:
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 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.