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Interactive Stealth Tutorial (Flash Needed)

Following info. taken from, written by F22 Raptor.

The F-22 Raptor is a new breed of super-fighter for the 21st century. It combines, speed, stealth, low upkeep, agility, and surprise to accomplish the necessary tasks at hand. 

 Stealth is a word that comes from ancient roots, meaning "to steal".  The F-22, JSF, F-117 and other planes use stealth.  Using this technology, one can infiltrate the enemy's defenses without (hopefully) being detected.

To be stealthy, the plane must fulfill these accomplishments:

1. be hard to see with the eye.
2. make no sound (muffling the engines).
3. Heat from engines and moving parts must be minimal.
4. The plane must absorb and scatter radar beams.
5. Contrails and other signs of planes should not be produced.
There are many ways of detecting planes, but the most common is radar.


Radar is (when simply put) radio waves thrown out into air that bounce off of objects, return to the place of origin, and when calculated, can tell what something is, how far it is, and how fast it's moving.

A basic, non-foolproof formula for calculating target distance using radar is:

target range= T/12.36 microseconds per nautical Mile

            where T=Elapsed Time

The Radar Cross Section of a plane is basically, how much echo the plane sends from radar.  Everything has a Radar Cross Section (or RCS), but where birds have approximately a .01 square meter RCS, the Raptor has almost the same RCS. The B2 Bomber has a radar cross section of .75 square meters. For the Raptor to be stealthy, the creators had to cut down on the RCS, meaning that everything on the plane, internal and external, had to have no echo, or as little as possible.  To accomplish this, they made many parts of the plane with special alloys (metal mixtures) that had little or no echo when hit by radar.  The shape of the F-22 is made to have an over-all "triangular" shape, making the over-all shape reflect radio waves in such a manner, that they do not go back to the radar of the enemy.  




RAM, or Radar Absorbing Material, is covering the entire fuselage of the F-22.  This material is made to absorb and kill radio waves instead of reflect them.


The F-117 is a prime example of scattering. The entire plane is one, large system of triangles.  It has all flat surfaces, angled to deflect radar waves away from enemy base.  The F-22 also does this, but in a different manner.  It is fairly rounded, yet on closer observation, the over-all shape has angles to it that scrambles the radar all over, everywhere but back to the radar's origin.


Heat Reduction

To be stealthy, a plane must not give off too much heat.  The heat not only makes it stand out on thermal imaging, but makes it a prime target for missiles.  The engines of the Raptor are made to make as little exhaust and heat as possible.


Turbulence Reduction

The turbulence of a plane is caused by the movement of the craft disrupting the air around it.  The shape of any stealth plane is made so that is EXTREMELY aerodynamic, having the least amount of air resistance. This minimizes the turbulence, and the fuel costs, since the plane is not creating so much drag.  The less turbulence, the less likely it is that the enemy's sensitive laser detection equipment will pick up on the plane.


Visual Detection:
*Smoke Contrails

Smoke Contrails are caused when the engine(s) of a plane spurts out extra power.  Any contrail (smoke or air) is something that a pilot does not want following his plane if he is going into the enemy territory, after all, it is a tell tale sign of his presence.  The F-22 and many other planes were created in such a way as to reduce this problem.  Tests were once conducted to stop or reduce contrails on planes.  The F-22, because of the super cruise ability, is able to avoid the smoke contrail problem fairly well.


* "Air" (moisture) Contrails

"Air" Contrails are the most commonly seen type of contrail. These come from the moisture in the air being disturbed by a wing.  When these contrails are created, the pressure of air surrounding the wing is disturbed and unbalanced, causing the moisture to form trails.  The F-22 has been able to decrease the likelihood of these contrails because of the horizontal stabilizers located on the aft part of the aircraft.  These stabilizers help evenly distribute the lift of the aircraft so that contrails are avoidable. 


*Low Visibility

The F-22 was painted with a medium gray.  This gray matches the sky closely enough to fool the naked human eye enough to not stick out like a sore thumb. 


*Low Level Flight

This is a somewhat dangerous, yet old and effective way of avoiding radar detection.  This method is used to fly below radar cover, basically, flying so low to the ground, that all the trees and obstacles (hills, buildings, etc.) scramble the radar waves (remember that radar bounces off of everything).  

This method is beginning to age.  With new detection methods, the radar is able to pick out the plane from the ground clutter. 

Following from F22-Raptor

"Stealth features of the F-22
Taking a look at the F-22, quickly reveals the fundamental principles of a stealthy design as discussed earlier.

Airframe features
The F-22 has a low height triangle appearance from the front. This physical cross sectional view ensures a small signature from the front and low observability touches such as paint and materials, as well as little "W" shapes where straight lines might have appeared, all tend to break up the signature by absorption or redirection.

The "W" shapes are found at numerous places on the stealth aircraft. For instance, in the forefront of the cockpit glass, there is a very apparent "W" shape. This reduces the radar energy reflected during a head-on pass to the radar emitter. The "W" shape is also found on landing gear doors, engine inlets and outlets, as well as other openings.

The leading and trailing edges of the wing and tail have identical sweep angles (a design technique called platform alignment). The fuselage and canopy have sloping sides. The vertical tails are canted. The engine face is deeply hidden by a serpentine inlet duct and weapons are carried internally.

Engine nozzles
Reduction of radar cross section of nozzles Is also very important, and is complicated by high material temperatures. The approach taken at Lockheed is to use ceramic materials. The ceramics may be either lightweight, parasitic sheets mounted on conventional nozzle structures or heavier structural materials forming saw-toothed edges.

The pilot's head, complete with helmet, is a major source of radar return. This effect is amplified by the returns of internal bulkheads and frame members. The solution is to design the cockpit so that its external shape conforms to good low radar cross section design rules, and then plate the glass with a film similar to that used for temperature control in commercial buildings. Here, the requirements are more stringent: it should pass at least 85% of the visible energy and reflect essentially all of the radar energy. At the same time, one would prefer not to have noticeable instrument-panel reflection during night flying.

On-board antennas and radar systems are a major potential source of high radar visibility for two reasons. One is that it is obviously difficult to hide something that is designed to transmit with very high efficiency, so the so-called in-band radar cross section is liable to be significant. The other is that even if this problem is solved satisfactorily, the energy emitted by these systems can normally be readily detected. The work being done to reduce these signatures is classified.

Paint scheme
In order to make the F-22 disappear for the human eye on the ground, when in flight, special camouflage schemes have been developed. This way the plane will blend with the background sky as much as possible viewed from the bottom and disappear in the ground texture when seen from above."

Interactive Stealth Tutorial (Flash Needed)


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