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.

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

Radar cross-section reduction

Some techniques are :-

1. Shaping the airframe2. Radar absorbing material (R.A.M).3. Plasma stealth.4. Infrared stealth.

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.

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.

ii. Difference between conventional & stealth aircraft design

When we are using normal shape

when using stealth technology.

iii .Engine position Normal fighter plane showing the engine.

Engines of the stealth aircraft are covered.

iv. Exhaust plume

EXHAUST PLUME OF A NORMAL PLANE.

STEALTH AIRCRAFT WITHOUT EXHAUST PLUME.

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.

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.

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.

4.Infrared stealthFor 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.

Result

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.

Situation of Stealth fighter aircrafts in air forces all around world

American F-22 Raptor is the only stealth aircraft in operation today.

ADVANTAGE

Stealth aircraft are invisible to radar.

Used to carry undercover operations.

 Develops the military secrets .

DISADVANTAGEStealth aircraft cannot fly as fast as conventional aircraft.

Stealth aircraft can only carry reduced amount of payload.

Cost of maintenance is high.

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)

RAH-66

Black Hawk