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Stealth

Technologyby

B.Gopinath

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Definition • Stealth technology is also known as LO

technology (low observable technology)

• The concept of stealth is to operate or hide withoutgiving enemy forces any indications as to their

presence.

• This concept was first explored throughcamouflage by blending into the background

visual.

• Varying degrees of stealth can be achieved in aparticular design by the prediction of likely

detection techniques. 

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Stealth Principles 

Stealth technology is not a single technologybut it is a combination of technologies as below

• Radar cross section reductions

• Acoustics

• Visibility

• Infrared

• Reducing radio frequency emissions 

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Radar Evasion 

• Almost since the invention of radar, varioustechniques have been tried to minimizedetection.

• Some of the techniques used for this purposeare: 

1. Vehicle shape 2. Non-metallic airframe 3. Radar absorbing material

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Vehicle shape 

• Behind the skin of some aircraft are structuresknown as re-entrant triangles. Radar wavespenetrating the skin of the aircraft get trapped inthese structures, bouncing off the internal faces

and losing energy

• Stealth design must bury the engines within thewing.

• Planform alignment is also often used in stealthdesigns which returns a radar signal in a directionaway from the radar emitter.

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Planform alignment 

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Shape of a stealth aircraft 

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Shape of a stealth ship 

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Non – Metallic Airframe • Dielectric composites are more transparent

to radar, whereas electrically conductivematerials such as metals and carbon fibers

reflect electromagnetic energy incident onthe material's surface.

• Composites which contain ferrites optimizethe dielectric and magnetic properties of thematerial for its application.

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Radar Absorbent Material  

• Radar-absorbent material (RAM), often aspaints, are used especially on the edges ofmetal surfaces.

• While the material and thickness of RAMcoatings is classified, the material seeks toabsorb radiated energy from a ground or airbased radar station into the coating andconvert it to heat rather than reflect it back.

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 Acoustics • Acoustic stealth plays a primary role in

submarine stealth as well as for groundvehicles. 

• Submarines have extensive usage of rubber

mountings to isolate and avoid mechanicalnoises that could reveal locations tounderwater passive sonar arrays. 

• Early stealth observation aircraft used slow-turning propellers to avoid being heard byenemy troops below. 

• Stealth aircraft that stay subsonic can avoid

being tracked by sonic boom 

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Covered Engines Of Aircraft 

l h l h h

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Normal Fighter Plane Showing The Engine 

l h l fl d h

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Stealth Plane Camoflauged to Match The Colour Of The Sky 

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Infra-Red  • An exhaust plume contributes a significant infrared signature.

One means of reducing the IR signature is to have a non-circular tail pipe in order to minimize the exhaust cross-sectional volume and by mixing of the hot exhaust with coolambient air. 

• Sometimes, the jet exhaust is vented above the wing surface inorder to shield it from observers below. 

• To achieve infrared stealth, the exhaust gas is cooled to thetemperatures where the brightest wavelengths it radiates onare absorbed by atmospheric carbon dioxide and water vapor,

dramatically reducing the infrared visibility of the exhaustplume. 

• Another way to reduce the exhaust temperature is to circulatecoolant fluids such as fuel inside the exhaust pipe, where thefuel tanks serve as heat sinks cooled by the flow of air along

the wings.

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Exhaust Plume Of A Fighter Jet 

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Stealth Aircraft Without Exhaust 

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Detection Methods 

• On a radar screen, aircraft will have their radar crosssections with respect to their size.

•

The relative size of a stealth aircraft on the radarscreen will be that of a large bird.

• A proven method to detect and destroy stealth aircraft

is to triangulate its location with a network of radarsystems. 

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Disadvantages 

• Stealth aircraft cannot fly as fast or is notmaneuverable like conventional aircraft.

• Another serious disadvantage with the stealthaircraft is the reduced amount of payload it cancarry.

• Its very costly when compared with theconventional aircrafts of its class. 

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