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STEALTH TECHNOLOGY:
A REVEALING
An investigative study on stealth technology.
What is it?
• RADAR to detect position of objects.
• Counter measures 1. ECM ( e.g. chaff
cartridges) 2. Non ECM
• Avoiding detection and innovating
deception .
• RCS reductions, acoustics, thermal and
other EM emissions
Examples
• F 117
• B-2 Bomber
• F-22 Raptor( From YF 23 Platform)
• SR-71 Black bird
• HMS Helsingborg
How is it achieved.
• Absorbs radar waves or deflects to other
directions.
• Minimizes heat and other emissions from
engine and other spots.
• Makes difficult to detect except closely.
Vehicle shape and structure
• Smooth edges maximum radio
wave reflectors.
• The size of a target's image on
radar is measured by RCS (σ )
• For a square flat plate of 1m2
area, σ=13982 m2 at 10 Ghz
Vehicle structure (contd..)
• Mainly plan form alignment.
• The leading edges of wing and
tail surfaces set at same
angles.
Vehicle structure (contd..)
• Use of re-entrant triangles
behind skin.
• Distinctive serrations used in
external airframes.
• Propulsion subsystem shaping.
• Now in research is fluidic
nozzles for thrust vectoring.
Radar Absorbing Materials
(RAM)
• RAMs often as paints used to
absorb RADAR signals.
• Iron ball paint, ferrite in polymer
matrix used.
• The cockpit canopy coated with
thin layer of indium tin oxide .
RAMs (contd..)
• Small cell foams painted or loaded with
absorbing ink.
• MAGRAM
• R- Card
• Absorbing honeycomb
• Transparent RAM
Other fields
• Reducing RCS alone not enough.
• More difficulty is reducing the IR
signature.
• Interest is near IR region.
(shorter than 10 µm)
IR Emission
• Major IR emission sources.
1. Tailpipe region
2. Turbojets have EGT’s of 1000oC
3. Exhaust gas plume
4. Hot engine parts
5. Aircraft skin (frictional heating)
6. Reflected and reemitted sunlight.
IR Reduction
• Using surface paints
• Non circular tail pipe
• Emissions from hot parts screened by
airframe.
• The plume mixed with cool air.
IR Reduction (contd…)
• IR best transmitted 2.5, 4 and
10 micron bands.
• IR outside window absorbed by
CO2
• Passive IR target acquisition
systems more used.
Electromagnetic emissions
• EM emissions other than IR .
• The greatest source is RADAR itself.
• Shutting down RADAR a solution
having negative effects.
• Radio /radar altimeters and Doppler
navigation systems.
EM emissions (contd…)
• Use of inertial navigation , laser or
millimetric wave system
• Other EM emissions
1. Radio communication
2. ECM exploited (passive listening)
3. Composite materials radiating
switching transients
• Passive sensors (LPI radar in F-22 ), LOS
communication, inertial navigation are
used.
Acoustics
• Most important for submarine &
ground vehicles.
• Rubber mountings, AIP system, slow
turning propellers etc.
Visibilit
y
• Matte paint, gray paint
in disruptive
schemes , yehudi lights ( active
camouflage).
How to counter.
• Background of stealth craft than
craft shall be searched for.
• High flying aircraft with SLAR, FLIR
etc are used.
• Same method advantageously used
using satellite.
Stealth counter (contd….)
• Uninterrupted radio waves from
stars mapped.
• Failure or fainter image suggests
probability of stealthy craft.
• Advantages of using lethal SAM’s
and remain undetected.
• Low frequency radar nullifies stealth
from shape.
Stealth counter (contd….)
• Disadvantages of LFR
1. Wavelength unavailability
2. Inaccuracy
3. Size
• 1. Bistatic radars
and
2. Using reflections from civilian radio
transmitters.
gives better detection.
Conclusion.
• Stealth technology developed a lot.
• Investment needed is very high.
• High chance of low cost gain.
• A lot learned about signature reduction
and absorption.
• Useful for other projects.
• Success yet to be proved extensively.
For the time
spared
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