STEALTH TECHNOLOGY

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STEALTH TECHNOLOGY IN AIRCRAFT
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BRIEFING ABOUT THE TECHNOLOGY
Stealth aircraft are aircraft that use stealth
technology to make it harder to be detected by
radar and other means than Conventional aircraft
by employing a combination of features to reduce
visibility in the visual, audio, infrared and
radio frequency (RF) spectrum. Well known
examples include the United States' F-117
Nighthawk (1980s-2008), the B-2 Spirit "Stealth
Bomber," and the F-22 Raptor.
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• Stealth is accomplished by using a complex design
  philosophy
• to reduce the ability of an opponent's sensors
  to detect, track
• and attack an aircraft .
• Modern stealth aircraft first became possible
  when a
• mathematician working for Lockheed Aircraft
  during the 1970s
• adopted a mathematical model developed by Petr
  Ufimtsev, a
• Russian scientist, to develop a computer program
  called Echo 1.

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Principles Of Radar

• Echo made it possible to predict the radar
  signature an aircraft
• made with flat panels, called facets.
• Echo can be considered as a wave bouncing off the
  surface and
• coming back to source.
• This principle can be used to detect time and
  distance of target .

Doppler shift is second principle of radar. This
can b used to detect the speed of target
approaching..
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• Reduced radar cross section is only one of five
  factors that
• designers addressed to create a truly stealthy
  design. Designers
• also addressed making the aircraft less visible
  to the naked eye,
• controlling radio transmissions, and noise
  abatement.
• The first combat use of stealth aircraft was in
  December 1989
• during Operation Just Cause in Panama. In 1991,
  F-117s were
• tasked with attacking the most heavily fortified
  targets in Iraq
• and were the only jets allowed to operate inside
  Baghdad's
• city limits

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Attention towards these aircrafts is made after
persian war II ,91 Night-enhanced images of the
otherworldly-shapedF-117s taking off in the night
and striking high-value targets with scarcely
believable precision and seeming invulnerability
to thick air defences were widely televised and
etched in the memories of TV viewers
worldwide. Loss of at least one F-117 in Kosovo,
has peeled off some of the mythical cloak
surrounding stealth.
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Different technologies and strategies
forSTEALTH
Ben Rich, the leader of the Lockheed team that
designed the F-117, has stated "A stealth
aircraft has to be stealthy in six disciplines
radar, infrared, visual, acoustic, smoke and
contrail. If you don't do that, you flunk the
course."
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• Different technologies and strategies for stealth
  are the province
• of land, naval and underwater forces.
• Underwater warfare will naturally hand dominance
  to the acoustic
• spectrum
• Land combat will emphasize visual, infra-red and
  acoustic
• signatures.
• Radar and (to a lesser extent) infrared bands
  dominate the scene of
• airspace surveillance, and so they have to
  be given higher priority
• when thinking the applications in air
  warfare.

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Signature Of A Vehicle
The signature can be stated as any activity or
radiation or characteristic of the body that
help to revile its presence at a particular
point. Observability of an object on detection
system can b called as signature of
vehicle. All detection methods used either in
military or civil applications use signature of
body as reference to detect that object.
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RADAR REFLECTIVITY

• All radar systems, from an AWACS to police speed
  radar, work in the
• same principle
• A certain amount of electromagnetic energy
• is transmitted through a directional antenna,
  which focuses it into a
• conical beam. When a reflective target blocks
  part of the beam, that
• part of the beam is reflected in many different
  directions, or "scattered."
• If the scattering is fairly random, as is usually
  the case, some energy
• will be reflected in the direction of the radar
  antenna. Most radar
• transmits this energy in pulses, thousands of
  them every second.

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In the gaps between the pulse transmissions, the
radar becomes a receiver, and the gaps are
carefully chosen to be just long enough for the
signal to make its way to the target and back at
the speed of light1. The time interval between
the transmission and reception of the pulse gives
the range from the radar to the target. The
radar antenna moves at a pre-determined regular
rate, so the time at which the target moves in
and out of the beam can be tied to the position
of the antenna, giving the target's bearing from
the location of the radar.
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Comparison between Human Eye Radar

• Humans see in a world which is saturated with
  visible light, so that
• almost every square inch of it reflects some
  light toward us at all times .
• The radar only "sees" the energy that is
  reflected toward it. The radar
• can detect a target ONLY when its antenna
  captures enough energy to
• rise above the electronic noise that is
  invariably present in the receiver.

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Variablesin the Transmission-scattering-Reflectio
n

• They all affect the maximum range of the above
  process. They are
• - The strength of the outgoing signal
• - The width of the beam
• - The size of the antenna
• - The reflectivity, or RCS, of the target.

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Process Diagram
Enemy Aircraft
Conical Beam
Reflected Beam
Scattered Rays
AWACS
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RCS
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RCSRadar Cross Section

• Out of radar designers control.
• RCS not directly proportional to detection range
  because of radial
• scattering effects and cannonical beam of radar.
• Radar cross section is the measure of a targets
  ability to reflect radar
• signals in the direction of the radar reciever
  i.e per unit solid angle.
• The conceptual definition of rcs includes the
  fact that not all of the
• radiating energy falls on the target .

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RCS

• The rcs is easily visualized as product of three
  factors.
• Rcs ()projected cross section
  reflectivitydirectivity.
• reflectivitythe percentage of power
  reradiated(scattered) by the target .
• Directivitythe ratio of power scattered back in
  radar direction.

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RADIATION SCATTERING BY TARGET

• The sphere is essentially same in almost all
  directions i.e. 360 degree
• The flat plane has has almost no rcs except when
  aligned directly towards radar i.e. 90 degree
• The corner reflector has an rcs almost high as
  flat plane over a wider angle i.e. 60 degree.

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Minimizing Rcs

• GEOMETRIC DESIGN

• RADAR ABSORBENT MATERIALS

• Conventional aircraft use round shape cone as it
  support principle of aerodynamics.
• The stealth aircraft is made up of flat surface
  and very sharp edges
• Radar signal heating the stealth plane are
  scattered in all directions by this.

• Metallic surfaces generally reflect the radar
  signals.
• There stealth aircraft should be coated with
  radar absorbent materials.
• Which deflect and absorbed incoming radar waves
  and reduce the detection range.
• Radar absorbent layer is present below the
  surface coating of aircraft using corner
  reflector.

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Minimizing Rcs

• GEOMETRIC DESIGN

• RADAR ABSORBENT MATERIALS

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Visual stealth

• Low visibility is desirable for all military
  applications
• Earlier stealth aircraft were painted black and
  thus could be used during nights
• Now days an electro chromic polymer is being
  developed for daytime stealth
• These polymer sheets sense nature of the
  surrounding and change there color accordingly

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Visual stealth
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Infra-red stealth

• Infra-red radiation are emitted by all matter
  above absolute temperature zero
• Hot zones such as engine exhaust , wing surface
  friction due to air get heated which rather
  increases the visibility
• These part should be kept cool as possible it can
  be
• Option would be mixing of cool air with the hot
  engine exhaust

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Infra-red stealth
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Acoustic stealth

• Acoustic cells involves the sound waves to
  detect the target
• Knowing the fact thats sound waves moves too
  slowly as compared to radio wave so it
  functionality should be directed towards low
  altitude flying aircraft and pre-dominantly ships
  and submarines.

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Plasma stealth

• In this stealth the aircraft injects a stream of
  ionized gas which envelopes the aircraft due to
  which most of the radar wave are observe this
  make the aircraft completely invisible

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Advantages of stealth

• Reduces the causality rates during war
• Saving military budget
• Develop the military secretes
• Bluff the anti-detective device

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Issues with stealth

• Stealth aircraft cannot fly as fast as
  conventional aircraft
• Can carry limited amount of load
• Very economic B-2 cost 2 billion ,F-22 100
  million
• Wing shape does not provide the optimum the lift.

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Conclusion

• Well to conclude the current scenario appears
  some things similar to the cold war both sides
  are accumulating weapons to counter each other
  and each side can be termed as stealth
  technology and the other as anti-stealth
  technology.
• Its an arm race except it isnt between specific
  countries .

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THANK YOU !
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IF ANY ?
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