If you wanna know how you can fly and how to get stealthy look at page
2.
If you are curious of what is going to happen in the futher have a look
at page 3.
At page 4 you can find what the futher of stealth will be.
Introduction
Continuous developments in military aircraft technology have produced
a new sort of defensive weapon: Stealth. Planes can now fly invisibly
into enemy airspace, drop a payload, and fly back out without being detected,
identified or attacked.
To meet this goal, an aircraft must be "stealthy" in many areas.
- 1. It must be very hard to detect on radar.
- 2. The hot emissions from the engines must be minimal.
- 3. It must be quiet
- 4. Its engines should not produce contrails or exhaust smoke in cold
atmosphere
- 5. It should be hard to see with the human eye
detection
Radar
Currently the way to detect and even identify aircraft, is the use of
radar. This system, invented during world war II, simply works by constantly
sending bursts of radio waves of certain frequencies and measure the echo's
of each burst.
Parts of the energy of radio waves are being reflected by objects. This
can be a plane, but also a cloud or a bird. Depending on the material
the object is made of, this echo is stronger or weaker, but there is an
echo. By measuring the reflected energy as a function of position and
time, computers can calculate what it is that reflects the energy, where
it is in 3D space and also in what direction it moves.
To get a proper overview of an area with radar, the transmitting and receiving
antenna should rotate in angles of 360 degrees. This is why you always
see these rotating antenna's at for instance airports and ships. To protect
the antenna's from damage, they are often mounted in a radio wave transparent
dome, which you will probably already have seen somewhere.
Radar echo's from the jet wake
The parameter determining radar return from a jet wake is the ionization
present. Return from resistive particles, such as carbon, is seldom a
significant factor. The very strong ion-density dependency on maximum
gas temperature quickly leads to the conclusion that the radar return
from the jet wake of an engine running in dry power is insignificant,
while that from an afterburning wake could be dominant.
Heat detection
Another way of detecting if an aircraft is flying somewhere is by measuring
the heat it radiates. Normally this heat is produced by the planes engines.
There are two significant sources of infrared radiation from air-breathing
propulsion systems: hot parts and jet wakes.
By using modern heat image sensors (read InfraRed sensors) the difference
can be seen between a flying object itself and the surrounding cold air.
This is the same for the jet engine exhaust gases.
The ideal case would be that the plane body and exhaust fumes have the
same temperature as the surrounding air, making it blend with its background
(seen from the detectors point of view.
Heat detection is often used in missiles which can lock themselves on
the hot jet-engine exhaust and thus flying themselves directly into the
planes most vital part. The Sidewinder is a good example of such a missile.
Turbulance detection
Turbulence detection Shape also has a lot to do with the `invisibility'
of stealth planes. Extreme aerodynamics keep air turbulence to a minimum.
Rumors are heard about sophisticated laser controlled turbulence sensors,
which can measure paths of disturbed air, generated by an aircraft which
just passed.
Visual Acoustic detection
Visual detetection Reducing smoke in the exhaust is accomplished by
improving the efficiency of the combustion chambers. Getting rid of contrails
- the white line in the sky caused by high flying planes - is a harder
task however. More about that later.
Acoustic detection
A very obvious source of detection is the noise, generated by jet engines.
Several systems have been designed in the meantime to reduce the sound
of jet engine exhausts to a minimum, making them harder to detect by just
measuring sound waves. But often it is already too late if you can hear
the plane...
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