Basically stealth is
a way of masking something from detection.
In the case of aircraft there
are 5 main points which need to be taken into consideration in order to achieve
this :
It must be very hard to detect on radar.
The hot emissions from the engines must be minimal.
It must be quiet.
Its engines should not produce contrails or exhaust smoke in cold
atmosphere.
It should be hard to see with the human eye.
So how do we detect aircraft?
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 off each burst.
Parts of the energy of radio waves will be
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 always 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 about 360 degrees. You will have seen these radars at
airfields and aboard ships.
To protect the antenna's from damage, they
are often mounted in a radio wave transparent dome, besides which, you will
invariable see a group of protestors chained to a fence.
So where does stealth come in?
Prior to the introduction of stealth technology, aircraft had to
rely on jamming radar detection systems. This was effective on the whole but not
fool-proof. Then someone had the bright idea of trying to design an aircraft
that was invisible to radars.
To make a stealthy aircraft, designers had
to consider five key ingredients:
Reducing the imprint on radar screens / stifling radio
transmissions.
They have just given the go
ahead to produce the F-22 Raptor which will be introduced into active service in
2004. It's packed full of all the latest gadgets and if you win the lottery
hundreds and hundreds of times on the trot, and you're wondering what to spend
your 1.5 billion on then what about this...
Imagine you
can electronically change the color of a given surface in such a way it can
match the terrain below it. Fly over forest, and the surface takes on a green
like hue. A cloudy day, add clouds to mimic what sensors see underneath and the
aircraft becomes a chameleon and disappears.
Recent breakthroughs in
chemical polymer technology have made it possible to create polymer (plastic)
color displays. In other words, mold the polymer in any shape you like and with
the additional control electronics you can make it virtually invisible from any
point of view.
This is not a new idea, in fact several military fiction
writers have already come up with the idea, in one particular instance having
the aircraft continually modifying top and bottom like a magician's mirror box
making the aircraft totally invisible. Incredible eh?!?
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