posted on Jun, 20 2004 @ 07:55 PM
FLYING IN RADAR INVISIBILITY
In the late 1950's the American CIA began sending Lockheed U2 spy-planes
over the Soviet Union to take intelligence photographs. The U2's
flew at 80,000ft (24,000m) to be out of range of anti-aircraft fire,
but it then became clear that radar was not detecting them.
These extraordinary planes were little more than jet-powered gliders
built of plastic and plywood. On takeoff they jettisoned their small
outrigger wheels from the ends of their wings and they landed on
their main retractable wheels in the centre.
It was not until May 1960, after more than four years of overflights,
that the Russians shot one down using new radar equipment belonging
to SA-2 surface-to-air missiles. And even then the U-2 did not receive
a direct hit. A missile exploded close enough to put the fragile
aircraft into an uncontrollable dive, and the pilot, Gary Powers,
had to eject.
The success of the U-2s led to highly classified research work
in the US, known as 'Stealth', to create a military aircraft that
was invisible to radar. The U-2 had gone undetected for so long
because it was made of non-metallic materials which absorbed radar
waves rather than reflecting them back to the radar ground station,
as normally happens.
The Stealth program aimed at designing high-performance military
aircraft incorporating, among other features, a minimum of metal
and with the exterior clad in highly absorbent tiles. The aircraft
would be almost invisible to radar and could make most radar-controlled
anti-aircraft systems obsolete.
After being developed under a blanket of secrecy, the high-tech
B-2 Stealth bomber was unveiled at the Northrop company's manufacturing
plant in Palmdale, California, in November 1988. An audience of
invited guests and journalists was kept well away from the plane
which was designed to slip through enemy radar defences without
being detected and then drop up to 16 nuclear bombs on key targets.
To help achieve radar invisibility, the bomber is coated with
radar-absorbent paint on its leading edge. A similar technology
is used underwater to foil sonar detection. Modern submarines are
coated in a thick layer of a top-secret resin which is highly absorbent
acoustically, and reflects only a minute amount of the energy transmitted
by sonar detectors.
Another technique used by aircraft to avoid radar is to fly at
very low levels where there is a great deal of 'ground clutter'
... radar reflections given off by buildings and other objects.
Low-level aircraft can go undetected by most radar systems. But
the latest, most sophisticated ground-defence systems are designed
to discriminate between ground-clutter and hostile planes. In addition,
ground-clutter is partly avoided by using 'look down' radar systems,
which track aircraft from other aircraft flying above.
In the Gulf War, you may have seen on TV, the Baghdad AAA - they
were getting bombed, but they didn't know by what, they were shooting
all over the sky hoping for a hit.
The skeleton of the F-117 is made mainly of aluminium. The aircrafts
skin, by contrast, is mostly composite RAM (Radar Absorbent Material).
The twin butterfly ( \/ ) tail obscures the exhaust plume from infrared
sensors aboard pursuing fighters. The idea of an unstable V-tail
was first tested on the Tacit Blue stealth aircraft. The Nighthawk's
twin General Electric engines are buried deep in the fuselage. That
have shallow "platypus" exhausts, which cool and deflect the exhaust
gases upward to minimise heat emissions. The edges of the F-117's
cockpit canopy, like all surfaces, have no right angles (right angles
are strong radar reflectors). The Stealth can be refueled in flight.
But rumors about the handling of the F-117, said it was somewhat
'erratic', especially when refueling. As a result, one of the first
nicknames for the plane was "Wobblin' Goblin".
Forty F-117's were deployed to the Gulf. Only 59 production F-117s
were built, yet the total cost of the program is over six billion
The latest addition to make use of stealth technology is Sikorsky's
RAH-66 Comanche helicopter. The most advanced helicopter in the
world, due to enter service in 2006, emphasizing low emission rotor
designs and sophisticated retracting gear and weapons bay systems.
Source information obtained from
the Department Of The Air Force