How do you make Invisible Ships, Planes & Tanks?

To the ancient Greeks it was called the
Helm of Hades or the cap of Hades a special helmet that would make the
wearer invisible. In Welsh and Germanic folklore as well as are all modern-day
fictional equivalent of Harry Potter there is the cloak of invisibility, a
magical item that can also make the wearer invisible so it would only seem
right that the military has been striving to create its own version of
invisibility as long as we’ve had camouflage but other than painting your
face green and brown and wearing grass on your head, what else has been done to
make the military invisible. Do you remember the film the
Philadelphia Experiment well just in case you haven’t seen it it’s about a
world war two experiment to make a US Navy destroyer, the USS Eldridge
invisible though in the film the field generator they use makes the ship
disappear and move through space and time and when it comes back strange
things have happened at a crew. Well the basis of the film is actually true to
make a ship invisible but not so as you couldn’t see it but invisible
magnetically so that it wouldn’t trigger magnetic mines.
This technique is known as Degaussing, effectively demagnetizing after the unit
of magnetism called the Gauss. During World War 2 the Germans used magnetic
mines which detected an increase in the Earth’s north magnetic field when a ship
passed over it, this was causing havoc with the British fleet in the North Sea
in the English Channel. In 1939 after recovering a mine
accidentally dropped on mudflats at low tide off of the southeast coast of
England, the British were able to work out how the mines worked and then
developed methods to reduce the magnetic effect. that the ships had. To degauss or
demagnetize the biggest ships, giant coils of wire were fitted around their
perimeters on things like aircraft carriers and troop carriers and several
thousand amps passed through them. This was powered by the ship’s generators
like a giant electromagnet and he added a slight south magnetic bias which
offset the magnetic effect of a ship near the mines. This had its limitations
as it could only be used on the biggest ships of enough electrical power to run
it and also where in the world it would be used because the Earth’s magnetic
field varies in strength in different locations,
it would also need to be reversed if it were to be used in the southern
hemisphere for example. Over time the mines became more sophisticated so today the latest degaussing systems can match the magnetic field of a ship to
background magnetic field anywhere in the world effectively making it
magnetically invisible. Now whilst this help protect the ships against mines
ships could still be seen by their biggest threat submarines. During the
first world war a technique of painting large abstract lines shapes and
contrasting colors over ships was developed called dazzle camouflage and
the ship’s gained the nickname of dazzle ships or razzle dazzle in the US. Now you
may be wondering why you would make a grey ship in the grey North Atlantic
standout with these massive abstract patterns but these were not to hide the
ship these confusing markings were to make it difficult for submarine
commanders to work out the ships type, heading and speed. From side on they helped disguise the shape by which the ships could be identified and from oblique
angles you can see what it makes it harder to work out which end is which
and thus the ships heading. This was to try and make the Germans get their
torpedo firing positions wrong so they would miss the ships. In World War one
and World War two over six thousand allied warships used these dazzle
patterns with each pattern being different. The problem was that because
everyone was different they couldn’t tell which patterns worked well and
which didn’t and as World War two progressed advances using planes and
radar made dazzle ships less relevant. Now the main enemy of a convoy of ships
was the u-boats and in World War two Allied planes were used to find and
attack submarines whilst they were still on the surface but the u-boat crews
could often see the planes approaching by the dark silhouettes against the
lighter sky and this gave them time to dive before the planes could engage. In
1943 the US Navy tried out a technique which had been developed by the Canadian Navy called diffused lighting camouflage. The US Navy created project Yehudi this
used lights similar to sealed beam car headlights mounted on the front of the
plane along the leading edges on the wings
these were automatically controlled by a photocell so that the brightness of the
lights matched that of the sky behind the plane this apparently simple idea
made the plane blend into the sky by breaking up the dark silhouette. The idea
was refined and in 1945 tests with a grumman Avenger showed that it was able to get within 2.7 kilometers of the target ship without being detected whereas
without the Yehudi lights it was visible 19 kilometers away.
Although these worked well by the time of the end of the war radar had made the
Yehudi light system pretty much redundant but that didn’t mean to say
that it was a bad idea, in fact it’s being the basis of many
ideas to apparently bend light around an object to make it appear invisible. The
most notable of these is adaptive camouflage which has only really been
possible in recent years with new electrochromatic materials and flexible
OLED displays. The principle is similar to the Yehudi lights but instead of
using a photocell they use a camera on the opposite side of the vehicle to which
it has been seen and this displays the image of what the camera is seeing onto
the watched side so effectively you don’t see the vehicle itself you just see what
you would see if it wasn’t there. Now close-up this wouldn’t fool anyone
but from far away it can help it blend into the background. Now whilst this
might work for visible light most weapons use infrared or heat to lock on
to their target so the latest active camouflage uses thermo-electric panels.
The system called adaptiv by BEA Systems has about a thousand or so of
these small hexagonal panels also known as Peltier panels which can be heated or
cooled by applying an electric current to them. Infrared cameras pick up the
background infrared radiation and relay this to the Peltier panels to
effectively hide the vehicle’s infrared signature from weapons or enemy spotters
by matching background infrared levels. As the sides
the vehicle are effectively now one large infrared display the shape of
another object can be projected onto it like in this example where the
silhouette of a tank is made to look like that of a car it could even flash
text messages which would only be seen in infrared. Now this isn’t the full
invisibility as we have seen in the movies but we are getting closer to
approximating it although you do have to say with what we know of current
technologies bending light around an object is going to take some serious
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