Stealth technology-Invisible to radar

2. INTRODUCTION
Stealth is technique in which we can make any object
(almost)invisible.
It also means VLO technology.
A stealth fighter has to be stealthy in five disciplines: radar, infrared,
acoustics, smoke and contrail.

3. History
The first stealth application was developed in Germany
during WW-2 in German submarines when they used Radar
absorbent paint on it.
In mid 1960’s, the U.S. built SR-71 Blackbird, that was
extremely RADAR-stealthy for its days.
SR-71 BLACKBIRD

4. Radar cross-section reduction
Some techniques are :-
1. Shaping the airframe
2. Radar absorbing material (R.A.M).
3. Plasma stealth.
4. Infrared stealth.

5. 1. Stealth shapes and design
i. Its tail should kept an Acute angle.
ii. Perfect nose design.
iii. Stealth aircraft must bury the engine within wings.
iv. Exhaust plume should be as small as possible.

6. i. Tail Angle Effect
A corner reflector of normal
aircraft is retroreflector consisting
of three mutually perpendicular
surfaces, which reflects EM waves
back to source.
So tail angle should be kept acute to
decrease detection.

7. ii. Difference between conventional &
stealth aircraft design
When we are using normal shape
 when using stealth technology.

8. iii .Engine position
Normal fighter plane showing the
engine.
Engines of the stealth aircraft
are covered.

9. iv. Exhaust plume
EXHAUST PLUME OF A NORMAL
PLANE.
 STEALTH AIRCRAFT WITHOUT
EXHAUST PLUME.

10. 2. Radar Absorbing Material(RAM)
R.A.M. is usually a Nano structural
composite material absorbing radar
waves.
R.A.M. is basically paint with which
external surfaces are coated with.
 These paints are Magnetic ferrite-based
substance such as carbon.

11. 3. Plasma Stealth
In this aircraft injects a stream of ionized
gas which envelopes aircraft due to which
most of RADAR waves are absorbed.
For system to work there has to be source
of energy which will ionize surrounding
air.

12. Drawbacks of Plasma stealth
Amount of power required is high.
It also blocks RADAR of aircraft itself being protected,
necessitating holes in plasma field to look through it.

13. 4.Infrared stealth
For detection, IR seekers look for contrasts between hot
parts on airframes such as jet pipes and surfaces subjected
to kinetic energy, and background radiations.
Methods to reduce IR signature :-
Plane should have ability to super cruise (cruise at speed of
super sonic speed)
Use curved jet pipes to mask hot turbine stages.
Use 2-dimensional nozzle which increases rate of cooling
by providing larger surface area for exhaust plume.
Increase cooling of outer skin or insulate to reduce
temperature of airframe skin.

14. Result

15. Situation of Stealth fighter aircrafts
in air forces all around world
Under construction planes :-
Chinese “Chengdu-J20” is in progress
and likely to join Chinese
force by 2015.
Russian-Indian Sukhoi T-50, expected to
join Russian air force by 2013 and
Indian air force by 2015.

16. Situation of Stealth fighter aircrafts in
air forces all around world
American F-22 Raptor is the only stealth aircraft in operation today.

17. ADVANTAGE
Stealth aircraft are invisible to radar.
Used to carry undercover operations.
 Develops the military secrets .

18. DISADVANTAGE
Stealth aircraft cannot fly as fast as conventional aircraft.
Stealth aircraft can only carry reduced amount of payload.
Cost of maintenance is high.

19. Conclusion
Stealth technology is step forward towards achieving
invisibility.
It is applied in military application so that aircrafts using this
technology are almost invisible to radar.
It can also used in Helicopter, some examples :-
i. RAH-66 Comanche.
ii. Black Hawk . ( both American)

20. RAH-66
Black Hawk