Stealth technology | Wikipedia audio article
Stealth. Technology, also, termed, low-observable. Technology. Low technology is a sub-discipline. Of military, tactics and passive, and also active electronic. Countermeasures. Which cover a range of techniques, used with personnel, aircraft, ships, submarines. Missiles. Satellites. And ground vehicles to, make them less visible, ideally, invisible, to radar infrared. Sonar. And other detection, methods. It. Corresponds. To military, camouflage for, these parts, of the electromagnetic. Spectrum multi, spectral camouflage. Development. Of modern stealth technologies. In the United, States began in 1958. Where, earlier attempts, in preventing, radar, tracking of its u-2 spy planes, during the Cold War by the Soviet, Union had been unsuccessful. Designers. Turned to develop a particular shape, for planes that tended to reduce detection. By redirecting. Electromagnetic. Waves from radars. Radar. Absorbent, material, was also tested, and made to reduce or block radar, signals, that reflect off from the surface of planes. Such. Changes, to shape and surface composition form. Stealth technology, is currently used on the Northrop, Grumman b-2 spirit, stealth, bomber. 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. Infrared, search and track 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. Is designed from the outset to, have a chosen, spectral, signature, the. Degree of stealth embodied, in a particular design, is chosen, according to the predicted, capabilities. Of projected, threats. Topic. History. The, concept, of camouflage, is known to predate warfare, itself, hunters. Have been using vegetation. To conceal, themselves perhaps, as long as people have been hunting in, England. Irregular, units of gamekeepers, in the 17th, century were, the first to adopt drab colors common, in 16th, century Irish, units, as a form, of camouflage following. Examples, from the continent, during. World. War one the germans, experimented with. The use of sellin cellulose, acetate a, transparent. Covering material, in an attempt to reduce the visibility, of military, aircraft. Single. Examples, of the fokker III, eindecker fighter monoplane. The albatross, CI two-seat. Observation. By plane and the linker Hoffman RI prototype. Heavy bomber were covered with Selin in. Fact, sunlight. Glinting, from the material, made the aircraft even more visible. Selin. Was also found to be quickly degraded. Both by sunlight, and in-flight temperature. Changes, so the attempt to make transparent, aircraft, was not preceded, with in 1916. The British modified. A small, SS, class airship, for the purpose, of nighttime, reconnaissance. Over German, lines on the Western Front. Fitted. With a silenced, engine and a black gas bag the craft was both invisible, and inaudible from, the ground but several nighttime, flights over German held territory, produced, little useful intelligence, and, the idea was dropped diffused.
Lighting Camouflage. A ship-borne form of counter, illumination. Camouflage, was, trialed, by the Royal Canadian Navy from, 1941. To 1943. The. Concept, was followed up but for aircraft, by the Americans, in the British in, 1945. A grumman Avenger, with Yehudi lights reached 3,000. Yards. 2,700. Metres from, a ship before being sighted, this. Ability was rendered obsolete by, radar, the u-boat u 480. May have been the first stealth submarine, it. Featured, an anechoic, tile rubber coating, one layer of which contained, circular, air pockets, to defeat as dick sonar. Radar. Absorbent. Rubber semi, two composite, paints, and materials, codenames, some. Sean. Stein Fedya were, used by the Kriegsmarine, on submarines, in World War two tests. Showed they were effective, in reducing radar. Signatures, at both short centimetres. And long, 1.5. Meters wavelengths. In, 1956. The CIA initiated. Attempts, to reduce the RCS, of the u-2, spy plane. Three. Systems, were developed trapeze. A series, of wires and ferrite beads around the platform of the aircraft, a covering, material, with PCB. Circuitry. Embedded, in it and radar-absorbent. Paint, these. Were deployed in the field on the so-called Dirty Birds, but results were disappointing the. Weight dragged increase, was not worth any reduction, in detection, rates. More. Successful. Was the application. Of camouflage, to the originally, bare metal aircraft, a deep blue was found to be most effective, the. Weight of this cost, 250. Feet in max altitude but, made the aircraft harder. To spot by interceptors. In. 1958. The US Central, Intelligence Agency. Requested, funding for a reconnaissance, aircraft to, replace the existing you, to spy planes and Lockheed, secured, contractual. Rights to produce it, Kelly, Johnson. And, his team at Lockheed, skunkworks, were, assigned to produce the a12, oxcart which. Operated, at high altitude, of 70,000. To 80,000. Feet in speed of mach 3.2 to. Avoid radar detection. Various. Plane shapes designed, to reduce radar. Detection, were developed, in earlier prototypes. Named, a12. A 11, the. A12, included, a number of stealthy, features, including, special, fuel to reduce the signature, of the exhaust plume, canted, vertical, stabilizers. The use of composite, materials, in key locations and, the overall finish in radar absorbing, paint in 1960. The USAF, reduced, the radar cross-section of, Orion q2c, fire, B drone, this. Was achieved through specially. Designed screens, over the air intake, radar, absorbent, material, on the fuselage, and a special, radar-absorbing. Paint during the 1970s. The US Department, of Defense launched. Project Lockheed, have blue with the aim of developing a, stealth fighter, there. Was fierce bidding between, Lockheed, and Northrop to, secure the multi-billion, dollar contract. Lockheed. Incorporated. Into its bid a text, written by the Soviet, Russian, physicist, plot EU ffensive from 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 US Air Force foreign, technology, division, the. Theory played a critical role in the design of American, stealth aircraft. F-117. And B two. Equations. Outlined, in the paper quantified. How a plane shape would affect its detect ability, by radar, its radar cross-section, RCS. This. Was applied by Lockheed, in computer, simulation. To design a novel, shape they called the hopeless. Diamond a wordplay, on the Hope Diamond securing. Contractual. Rights to produce the. F-117. Nighthawk starting, in, 1975. In. 1977. Lockheed produced, to 60%, scale. Models, under the have blue contract. The. Have blue program, was a stealth technology, demonstrator. That lasted, from, 1976. To 1979.
Also. The Northrop Grumman tacit, blue played a part in the development of composite, material, and curvilinear, surfaces. As well as low observables. Fly-by-wire. And, other stealth, technology, innovations. The. Success, of have blue LED the Air Force to create the senior, trend program, which developed, the f-117. Topic. Principles. Stealth. Technology, or low 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. Topic. Radar. Cross-section. RCS. Reductions. Almost, since the invention of radar, various, methods have been tried to minimize detection. Rapid. Development, of radar, during World War two led to equally, rapid development, of numerous counter. Radar measures during the period, a notable, example of, this was the use of chaff. Modern. Methods include, radar, jamming, and deception. The. Term stealth. In, reference, to reduced, radar signature, aircraft, became popular, during the late 80s, 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 caused the United States, invasion, of Panama, in 1989. Topic. Vehicle. Shape. You. Topic. Aircraft. The, possibility. Of designing aircraft, in, such a manner is 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. Despite. Being designed before, a low radar, cross-section, RCS. And other stealth factors, were ever a consideration. A royal aircraft establishment. Technical. Note of 1957. Stated. That of all the aircraft so, far studied, the Vulcan appeared by far the simplest radar, echoing object, due to its shape only one or two components. Contributing. Significantly to, the echo at any aspect, one of them being the vertical stabilizer which, is especially relevant, for side aspect RCS. Compared, with three or more on most other types. While. Writing, about radar, systems, authors, Simon, Kingsley, and Sean Creegan singled, out the Vulcan shape is acting to reduce the RCS. In. Contrast. The tupolev 95, Russian, long-range, bomber nato reporting name, bear, was conspicuous. On radar, it. Is now known that propellers. And jet turbine, blades produce, a bright radar, image the bear has four pairs of large, 5.6. Meter diameter contra-rotating. Propellers. Another. Important. Factor, is internal, construction. Some. Stealth aircraft have, skin that is radar, transparent. Or absorbing, behind, which a structures, termed reentrant, triangles. Radar. Waves penetrating. The skin get trapped in these structures reflecting. Off the internal faces. And losing energy, this. Method, was first used on the Blackbird, series, a-12, yf-12, a, Lockheed, sr-71. Blackbird. The most efficient, way to reflect, radar, waves back to the emitting 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 Taylor set at right angles. Stealth. Aircraft such, as the f-117. Use. A different, arrangement tilting. The tail surfaces, to reduce corner, reflections, form between them a more. Radical method, is to eliminate the, tail completely. As in the b-2, spirit, the. B-2s, clean, low drag flying, wing configuration. Not only gives it exceptional range. But also reduces. Its radar profile, the. Flying wing design, most closely, resembles, a so called infinite flat, plate as vertical. Control surfaces. Dramatically. Increase RCS, the perfect, stealth shape as it would have no angles to reflect back radar, waves. 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 extant aircraft, install, baffles, in the air intakes, so that the compressor, 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 unsteady, when, a door or hatch opens. Parallel. Alignment of edges or even surfaces. Is also often used in stealth designs. The. Technique involves using, a small number of edge all orientations, in the shape of the structure, for example, on, the f-22. A raptor, the leading edges of the wing and the tail planes are set at the same angle other, smaller. Structures. Such, as the air intake, bypass doors in the Air Refueling aperture. Also use the same angles. The. Effect of this is to return a narrow radar, signal, in a very specific, direction away, from the radar emitter rather than returning a diffuser signal did at, many angles. The. Effect, is sometimes called, glitter. After. The very brief signal, seen when the reflected, beam passes across a detector. It. Can be difficult, for the radar, operator, to distinguish, between a glitter event, and a digital glitch, in the processing, system. 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 parallel, alignment of features, this time on the external airframe. Shaping. Requirements. Detract, greatly, from an aircraft's, aerodynamic properties. The. F-117. Has. Poor aerodynamics. Is inherently, unstable and cannot be flown without a fly-by-wire. Control. System. 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 reflect. Off objects, the inside, of a cockpit has a complex, shape with a pilot, helmet alone forming, a sizable, 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 pilot, vision. Topic. Ships. Ships. Have also adopted similar, methods, though. The earlier arleigh burke-class destroyer. Incorporated. Some signature, reduction, features, the norwegian sholde class corvette was the first coastal, defense in the french la fayette class frigate, the first ocean-going, stealth, ship to enter service, other. Examples. Of the Taiwanese - o chang stealth corvette, german, Saxon class frigates, the Swedish, Visby class corvette the USS, san antonio, amphibious, transport dock and most modern warship, designs. Topic. Materials. You. Topic. Nonmetallic. Airframe. Dielectric. Composites. Are more transparent. To radar, whereas electrically. Conductive, materials. Such as metals, in carbon, fibers, reflect, electromagnetic. Energy incident on the material, surface.
Composites. May also contain, ferrite, to optimize, the dielectric, and magnetic, properties of a material for its application. Topic. Radar-absorbing. Material. Radar-absorbent. Material, RAM often, as paints are used especially on, the edges of metal, surfaces. While. The material, and thickness of Ram coatings, can vary the way they work is the same absorb, radiated, energy from a ground or air based radar station, into the coating, and convert it to heat rather, than reflect, it back, current. Technologies. Include, dielectric. Composites, and metal fibers, containing, ferrite, isotopes. Paint. Comprises. Depositing, pyramid-like, colonies. On the reflecting, superficies. With the gaps filled with ferrite, based Ram the. Pyramidal, structure, deflects, the incident, radar energy in the maze of RAM a, commonly. Used material. Is known as iron ball paint, iron. Ball paint contains, microscopic iron. Spheres that resonate, in tune with incoming, radio waves and dissipate, the majority, of their energy as heat leaving little to bounce back two detectors. FSS. Are planar periodic. Structures, that behave like filters, to electromagnetic. Energy, the. Considered, frequency. Selective, surfaces, are composed, of conducting, patch element pasted, on the ferrite layer. FSS. Are used for filtration and, microwave, absorption. Topic. Radar. Stealth, countermeasures. And limits. You. Topic. Low-frequency. Radar. Shaping. Offers, far fewer 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 radars, size making, it difficult to transport, a, long. Wave radar, may detect a target, and roughly locate it but not provide, enough information to, identify, it target, it with weapons, or even to guide a fighter to it. Topic. Multiple. Emitters. Much, of the stealth comes, in directions, different than a direct return. Thus. Detection. Can be better achieved, if emitters, are separate from receivers. One. Emitter separate, from one receiver, is termed be static, radar one or more emitters, separate, from more than one receiver, is termed multi static radar. Proposals. Exist to use reflections. From emitters, such as civilian, radio, transmitters. Including. Cellular, telephone, radio towers. Topic. Moore's law. By, Moore's law the processing, power behind radar, systems, is rising, over time, this. Will eventually, erode the ability, of physical, stealth to hide vehicles. Topic. Ships, wakes, and spray. Synthetic. Aperture, side-scan. Radar can. Be used to detect the location and, heading of ships from their wake patterns. These. Are detectable, from orbit, when, a ship moves through a Seaway, it throws up a cloud of spray which can be detected by radar. Topic. Acoustics. Acoustic. Stealth plays a primary role in, submarine, stealth as well as for ground vehicles. Submarines. Use extensive. 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 as, the Blackbird, relied more on its extremely, high speed and altitude. One. Possible, technique, for reducing helicopter. Rotor noise is modulated, blade spacing. Standard. Rotor blades are evenly spaced, and produced, greater noise at a particular frequency, in, its harmonics. Using. Varying, degrees of spacing, between the blade spreads, the noise or acoustic, signature, of the rotor over, a greater range of frequencies. Topic. Visibility. The, simplest, technology, is visual 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, in daylight stealth, especially. By the USAF, has, emphasized, the use of gray paint in disruptive, schemes and it is assumed that yahoodi lights could be used in the future to hide the airframe, against, the background of the sky including at night aircraft. Of any color appear, dark or as a sort of active camouflage. The. Original, b2, design, had wing tanks, for a contrail, inhibiting, chemical, alleged by some to be chloro, fluoro sulphonic. Acid but this was replaced in the final design with a contrail, sensor, that alerts the pilot, when he should change altitude and, mission planning also considers, altitudes, where the probability, of their formation, is minimized, in.
Space. Mirrored, surfaces, can be employed to reflect, views of empty space toward known or suspected observers. This approach is compatible, with several radar, stealth schemes. Careful. Control of the orientation. Of the satellite relative. To the observers, is essential, and mistakes, can lead to detect ability enhancement. Rather than the desired reduction. Topic. Infrared. An exhaust. Plume contributes. A significant. Infrared, signature. One, means to reduce IR, signature, is to have a non circular, tailpipe, a slit shape to minimize the exhaust cross sectional, area and maximize, the mixing of hot exhaust, with cool ambient, air C Lockheed, f-117. Nighthawk. Often. Cool air is deliberately, injected, into the exhaust flow, to boost this process, see Ryan a QM 91. Firefly. And Northrop Grumman b-2 spirit. According. To the stefan-boltzmann, law this, results, in less energy, thermal radiation in, infrared spectrum. Being released and thus reduces, the heat signature. Sometimes. The jet exhaust is vented above the wing surface, to shield it from observers. Below as in the Lockheed f-117. Nighthawk. And the unstuff, ii fairchild, republic a-10. Thunderbolt 2 to. Achieve infrared, stealth the exhaust gas is cooled to the temperatures, where the brightest, wavelengths, it radiates, are absorbed, by atmospheric, carbon dioxide and. Water vapor dramatically. Reducing, the infrared, visibility, of the exhaust plume. Another. Way to reduce the exhaust temperature. Is to circulate, coolant fluid, such as fuel inside the exhaust pipe where the fuel tank service 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. Topic. Reducing. Radio, frequency. RF, emissions. In, addition, to reducing infrared. And acoustic, emissions, a stealth, vehicle must avoid radiating. Any other detectable. Energy, such as from onboard radars. Communication. Systems, or RF, leakage, from electronics. Enclosures. The. F-117. Uses. Passive, infrared and low light level, television, sensor, systems, to aim its weapons, in the f-22. Raptor, has an advanced, LPI radar, which can illuminate, enemy, aircraft, without triggering a radar, warning receiver, response. Topic. Measuring. The, size of a targets, image on radar, is measured by the radar, cross-section or, RC s often represented. By the symbol, Sigma and expressed, in square meters, this. Does not equal geometric. Area a perfectly. Conducting sphere of projected, cross-sectional, area 1 square, meter ie a diameter, of one point 1 3 meters. Will have an RCS, of 1 square, meter, 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 square, meter will have an RCS, of Sigma, equals 4 PI a 2 lambda, 2 where, a equals area, lambda, equals wavelength, or, 13,000. 982. Square, metres, at ten gigahertz if, the radar is perpendicular, to the flat surface, 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, if. The. RCS, was directly, related to the targets, 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 by absorbing, it the target achieves a smaller radar, cross-section. Topic. Tactics. Stealthy. Strike aircraft, such as the Lockheed, f-117. Nighthawk. 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, 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, even. If a stealth aircraft is, detected, fire control, radars, operating. In c x and qu bands cannot, paint for missile guidance low, observable, low jets except, at very close, ranges. 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 enemy radar, locations. In 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, to. Be able to fly these safe. Routes. It is necessary, to understand, an enemy's radar coverage, see electronic, intelligence. Airborne. Or mobile radar, systems, such as a WACS, can complicate, tactical. Strategy, for stealth operation. Topic. Research. After. The invention of meta surfaces, the conventional, techniques, of reducing, RCS, have significantly. Been improved, as. Mentioned, earlier the primary, objective, in purpose, shaping, is to redirect scattered. Waves away from the backscattered, direction, or the source, however. It compromises. The performance, in terms of aerodynamics. One. Feasible, solution, which has extensively, been explored, in recent, time is to utilize meta, surfaces, which can redirect, scattered. Waves without altering, the geometry. Of the target. Such. Meta surfaces, can primarily, be classified, in two categories I, check, aboard meta surfaces, eat gradient, index meta surfaces. Similarly. Negative index, meta materials, or artificial. Structures, for which refractive. Index has a negative, value for some frequency. Range such as in microwave, infrared. Or possibly, optical, these. Offer another way to reduce detectability. And may provide, electromagnetic. Near invisibility, in designed wavelengths. Plasma. Stealth is a phenomenon, proposed, to use ionized, gas plasma, to reduce RCS, of vehicle's. Interactions. Between, electromagnetic. Radiation. And ionized, gas have been studied, extensively for. Many purposes including, concealing. Vehicles, from radar. Various. Methods might form a layer or cloud of plasma around the vehicle to deflect or absorb radar, from simpler, electrostatic. To RF more complex, laser discharges. But these may be difficult. In practice several, technology. Research and development, efforts exist, to integrate, the functions, of aircraft, flight control, systems, such as ailerons, elevators. Elavon, x' flaps, and flaperons, into, wings to perform the aerodynamic. Purpose, with the advantages, of lower RCS, for stealth via simpler, geometries. And lower complexity. Mechanically. Simpler, fewer or no moving parts, or surfaces. Less maintenance, and lower maths cost, up to 50%, less drag, up to 15%. Less, during, use and inertia. For faster, stronger, control, response to chain vehicle, orientation, to reduce detection. Two, promising, approaches, of flexible, wings and fluidics. Inflexible. Wings, much or all of the wing surface can change shape in flight to deflect airflow. Adaptive. Compliant, wings are a military and commercial effort, the, x53. Active. Aero elastic wing, was a US Air Force Boeing. And NASA effort. In. Fluidics. Fluid, injection is being researched for use in aircraft to control, direction, in two ways, circulation. Control, and thrust vectoring, in, both. Larger. More complex, mechanical. Parts are replaced by smaller simpler, fluidic, systems, in which larger, forces in fluids, are diverted, by smaller jets or flows of fluid intermittently. To change the direction of vehicles. In. Circulation. Control. Near the trailing edges of wings aircraft. Flight control, systems, are replaced by slots, which emit fluid flows. Topic. List, of stealth aircraft. F-117. Nighthawk. B-2. Spirit. F-22. Raptor. F-35. Lightning, ii. J. 2257. Topic. List, of stealth ships. You. Topic. See also. Horton. Brothers german, engineers, whose planes were the models for the stealth bombers.
Multispectral. Camouflage. Petty. Offensive. Soviet, russian, physicist, who created much of the original, theory behind radar, stealth. Radar.