Tài liệu STEALTH TECHNOLOGYSTEALTH TECHNOLOGY: A REVEALING ppt

STEALTH TECHNOLOGY:
STEALTH TECHNOLOGY:
A REVEALING
A REVEALING


An investigative study on stealth technology.
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.
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Absorbs radar waves or deflects to other
directions.
•
Minimizes heat and other emissions from
engine and other spots.
•
Makes difficult to detect except closely.
•
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 1m
2
area, σ=13982 m
2
at 10 Ghz
Vehicle shape and structure
•
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.
Vehicle structure (contd )
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 .
•
Small cell foams painted or loaded with
absorbing ink.
•
MAGRAM
•
R- Card

•
Absorbing honeycomb
•
Transparent RAM
RAMs (contd )
Other fields
•
Reducing RCS alone not enough.
•
More difficulty is reducing the IR
signature.
•
Interest is near IR region.
(shorter than 10 µm)
•
Major IR emission sources.
1. Tailpipe region
2. Turbojets have EGT’s of 1000
o
C
3. Exhaust gas plume
4. Hot engine parts
5. Aircraft skin (frictional heating)
6. Reflected and reemitted sunlight.
IR Emission
IR Reduction
•
Using surface paints
•
Non circular tail pipe

•
Emissions from hot parts screened by
airframe.
•
The plume mixed with cool air.
•
IR best transmitted 2.5, 4 and
10 micron bands.
•
IR outside window absorbed by
CO
2
•
Passive IR target acquisition
systems more used.
IR Reduction (contd…)
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.
•
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.

EM emissions (contd…)
Acoustics
•
Most important for submarine &
ground vehicles.
•
Rubber mountings, AIP system, slow
turning propellers etc.
Visibility
•
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.
•
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.
Stealth counter (contd….)

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