SEMINAR PRESENTATIONON

STEALTE TECHNOLOGY AND ITS APPLICATION IN AIRCRAFTS

BY :ANUJ GUPTA

0904016

SUBMITTED IN THE PARTIAL FULFILLMENT OF B.TECH DEGREE:

DEPARTMENT OF MECHANICAL ENGINEERINGDCRUST MURTHAL

STEALTH TECHNOLOGY AND APPLICATIONS IN AIRCRAFTS

INTRODUCTIONStealth is technique in which we can make any

object (almost)invisible. It also means very low observable or VLO

technology, in which object is made less visible to radar system, sonar, infrared and other detective methods.

A stealth fighter has to be stealthy in five disciplines: radar, infrared, acoustics, smoke and contrail.(visible condensation of water drops or ice crystals from atmosphere on wake of plane)

History The first stealth application was developed in

Germany during WW-2 in German submarines when they used Radar absorbent paint on it.

Later Americans worked on it and succeeded.

In mid 1960’s, the U.S. built a high altitude reconnaissance aircraft, the Lockheed SR-71 Blackbird, that was extremely RADAR-stealthy for its days.

SR-71 BLACKBIRD

Before Stealth, we need to know :-What is RADAR?

How it works?

Typical air defense structure of major countries.

What is RADAR ?RADAR is acronym for “Radio detection and ranging”. It was first developed in England in mid 1930s.Later in the WW-2 Germans also exploited RADAR to

gain significant defensive advantage.Tactics and techniques applied during World War-2

opened a new era in air combat in which the survivability of an airborne force was now dominated by radar in the detection phase.

After RADAR’s advent, conditions forced fighter plane designer for pursuing counters to radar-based defenses.

How Radar works ?

Typical structure of air defense system

RADAR ReflectivityAll RADAR system from AWACS (Airborne

warning and control system) to police speed RADAR, work on same principle.

The RADAR can detect a target only when its antenna capture enough energy to rise above electronic noise that is invariably present in receiver.

RADAR reflectivity depends on :-1.The strength of outgoing signal.2.Width of beam.3.Size of antenna.4.Reflectivity (RCS) of target

Radar cross-section (R.C.S.)R.C.S. is measure of how detectable an object is

with RADAR.This most important aspect in making the aircraft

stealthy as other factors contribute very less in detection of fighter aircrafts.

A very large reduction in RCS, not 1/10 but 1/1000, is essential to have a tactically significant effect (e.g. an 82% range reduction at 1/1000.).

This is what makes stealth possible and worth the effort is that such tremendous reduction in airframe is achievable and reason why achievable is that conventional non stealthy aircrafts are almost idle RADAR targets.

Radar cross-section reduction Almost since invention of radar, various

techniques have been tried to minimize detection

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 or fuselage.

iv. Exhaust plume should be as small as possible.

i. Tail Angle EffectA corner reflector is

retroreflector consisting of three mutually perpendicular, intersecting flat surfaces, which reflects electromagnetic 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.

2. Radar Absorbing Material(RAM)

Nanostructural composite material, absorbing without reflection radar wave.R.A.M. is basically paint with which external surfaces are coated with. These paints are Magnetic ferrite-based substance having ingredients dielectric, such as carbon. RAM reduces the radar cross section making the object appear smaller.

3. Plasma Stealth In this aircraft injects a stream of ionized gas which envelopes aircraft due which most of RADAR waves are absorbed.

For system to work there has to be source of energy which will ionize surrounding air , probably on leading surface, since resulting ions are in boundary layers & will follow airflow around plane.

Plasma stealth It comes with some drawbacks as :-Amount of power required is quite high.As power requirement is high, it is likely to be

activated in enemy territory.The other drawback is that, it also blocks RADAR

of aircraft itself being protected, necessitating holes in plasma field to look through it.

This technology was first tested on flying models and then on actual aircraft, named Russian Su-27 IB, and likely to be the first stealth fighter with this critical technology.

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

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

Situation of Stealth fighter aircrafts in air forces all around world

Under construction planes :-

Chinese “Chengdu-J20” is in progress and likely to be hand over to Chinese force by 2015.

Russian-Indian Sukhoi T-50, has passed many tests and expected to join Russian air force by 2013 and Indian air force by 2015, after mass production is possible.

ADVANTAGE

Stealth aircraft are invisible to radar .

Results in decrease in safety of plane.

 Develops the military secretes .

DISADVANTAGEStealth aircraft cannot fly as fast or is not

maneuverable like conventional aircraft.

Another serious disadvantage with the stealth aircraft is the reduced amount of payload it can carry.

On the other hand a conventional aircraft can carry much more payload than any stealth aircraft of its class. 

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

References :-

Wikipedia.org

Howstuffworks.com

Military-aircraft.org

Flymig.com

Paper “Analogues of stealth”, by Robert P. Haffa, Jr. and James H. Patton, Jr.1, etc..