Proximity Fuze – The 3rd Most Crucial Development of WW2Jun 09, 2021
In the realm of top secret World War II projects there are a couple of which
mostpeople will have heard of the
developmentof the atomic bomb with the Manhattan project and radar, but there was another that was classified as equally important and secrecy and its effect on The war could have been said to have been greater than the atomic bomb, and yet few outside the military knew about it until after the war. This is the story of the
proximityfuse, one of the best kept secrets of World War II and considered by some to be the third
developmentafter the atomic bomb and radar, here's how they worked and how this simple principle changed the outcome of the war.
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It was similar to trying to shoot a fly in a dark room with a peashooter, it reportedly took around a thousand rounds to shoot down a plane, with the advent of radar fire control and variable timing fuses, it was said. which were around 500 shells but these were very low estimates some sources said they could have been as high as 20 000 shells either way it was very ineffective and some saw it as simply harassing German bombers rather than an effective weapon The device that controls when the projectile A rocket or bomb explodes is called a
fuzeand in a projectile, for example, it fits into the top of the projectile and there are different types of
fuzes available depending on how you want the projectile to function at the start of a war.
Anti-aircraft projectiles are used. direct contact fuses which only worked if they hit the target or variable time or vt mechanical fuses, these activated a timer once the projectile was fired and then detonated after a predetermined time, allowing the gunners to place the detonations at a specific altitude that was determined through observation and radar and where they thought enemy aircraft were flying, but this was far from ideal because each had to be set by hand at the correct time before use and would then need to be fired. between approximately 10 and 15 to confirm Altitude adjustments could be seen by the enemy, who could move up or down and then avoid them.
If the fuse timer went out for one second, in any case, the projectiles would harmlessly detonate hundreds of meters above or below the target. The problem was not new and in the 1930s several ideas were proposed for ways to make projectiles detonate when they approached a target. The British had worked on radar-guided projectiles that could explode via a radio signal when seen. be close to a plane on a radar screen, but it proved too difficult to control precisely. What was needed was a way for the projectiles themselves to detect the plane and then detonate when they were close enough.
Another idea that occurred to a British man was to use a small transmitter in the fuse of the projectile, this would transmit a constant radio signal that would radiate outwards and be reflected by anything, such as an airplane that was within range; The reflected radio waves would be picked up by the body of the fuse, which was also the antenna, the difference between this and the transmitted signal created a beat frequency which increased as the projectile and fuse approached the target, this was It amplified, filtered, and then, when it reached a preset amplitude, activated an electronic switch, a fibrotron, which initiated the detonation process.
As the amplitude of the thyrotron firing signal was proportional to the distance from the target, it could be tuned to certain distances, usually between 6 and 20 metres, before detonating the projectile that hurled shrapnel at the target. There was only one problem: the acceleration of the forces experienced by a projectile in recoil or when fired weighs around 20,000 g, but that's not all, the projectiles are also fired along rifled barrels, which imparts a rotation that could be up to 30,000 revolutions per minute, also creating very large centrifugal forces. Today, this wouldn't be a problem with our modern solid-state transistors and integrated circuits, but back then all they had were glass vacuum tubes that were large and delicate and broke easily if a radio was dropped on the floor. ground and much less so if exposed to 20,000 g.
Although the British developed miniature reinforced tubes, this was still a major problem, so most British work focused on rocket and bomb fuzes that had g forces of less than a hundred. The british plans for the fuzes were also part of the tizzard mission which gave the united states many top secret british project plans for further development and production in case england was invaded by germany in the united states in 1940, Scientists at the Johns Hopkins Applied Physics Laboratory working with Navy and Army research laboratories had come up with a new modified design with separate transmitter and receiver circuits, but most importantly they had access to vacuum tubes. miniature ones that were initially made for headphone amplifiers and could fit in a breast pocket to test the effects of acceleration.
They placed a fly in an empty casing and shot it vertically when they retrieved the casing from the ground the fly was nowhere to be seen it was only when they inspected it very carefully they found a slight residue left on the inside of a casing and that was all they found. left from flying at such extreme accelerations the mass of the electronics became the limiting factor the smaller they were the better they would perform and the more reliable they would be along with miniature tubes and smaller, stronger resistors and capacitors the overall mass reduction was on the order of 10 times that of a conventional tube design, even things like solder for the joints, which would normally be made of lead and tin, would become a problem at such G forces, so a type had to be used. welding special that was only available in England.
Four vacuum tubes were used in the design to transmit and receive the signal, amplify it, and then trigger detonation. Some of the tubes were optimized with a flat electrode design that made them stronger. You might think that wrapping the glass tubes and electronics in a shock-absorbing layer would be enough, but this could actually induce vibrations with multiple harmonic resonances that could then break the glass and damage the other electronics, so The entire assembly would have to be as solid as possible, so they were encapsulated with a special wax that Now having an electronically controlled fuse that was sensitive to almost anything around it would be a major problem when handled on the battlefield. .
The last thing I wanted was for it to detonate in the barrel of the gun or be dropped, for example, so there were five of them. Safety features built into the design, firstly normal dry cell batteries were a problem, they had a limited lifespan and the fuses had to be ready to use without any additional work needed once they left the factory instead of a normal dry cell battery they used. a vial of acid that ruptured upon firing and activated the battery the spin imparted by a rifled barrel then ensured that the acid was distributed within the battery the detonator a small electrically operated explosive that activated the detonator was short-circuited by a switch mercury so that it would not work until the fuse began to rotate at high speed while traveling along the barrel of the gun and an out-of-line powder train between the detonator and the detonator would only align once the projectile was rotating to stop premature detonation in the barrel o When the projectile passed over friendly forces, a time delay was built into the discharge circuit of the capacitor that set off the firecracker.
This gave enough time for the projectile to be far enough away before it could detonate and to stop the fuse which was top secret at the time. Upon falling into enemy hands, a mechanical twist switch was activated by the rotation of a projectile. If a firecracker's discharge capacitor was charged and the projectile had not approached an enemy target, the spin was slowed and this activated the switch to self-destruct the projectile. and the fuse, in fact, until the D-Day landings, the use of
proximityfuses was only allowed over water, so if one failed, it would be lost at sea after the Japanese attack on Pearl Harbor in 1941, the Testing and production of the fuses were given top priority and work continued throughout 1942, although 20 percent of the projectiles fired did not work, the others proved to be very effective against drones, to the point that the commander of the firing range where testing was taking place complained that they were destroying too many of them.
Their drones, after many tests and refinements, were ready to be used in the Pacific against Japanese aircraft. On January 5, 1943, the cruiser Helena, using five projectiles with proximity fuzes, was the first to shoot down a dive bomber as the ship approached. With two salvos of projectiles they were soon being used by many of the region's ships with spectacular results. In May 1945, the destroyers Evan and Hadley were off the coast of Okinawa when more than 150 kamikaze aircraft attacked both ships using proximity fuses during All of the attacking aircraft were shot down and only six partially destroyed aircraft or parts of them managed to reach the ships.
According to the official report, the horizon from east to northwest was filled with burning planes. After the war, the Japanese stated that the astonishing accuracy of American anti-aircraft guns in destroying their dive bombers without hitting them was one of the reasons they began using kamikaze attacks and although they suspected something like a fuse was being used proximity, they didn't know how the Americans did it. The fuzes also worked at low altitudes, as they would detect the ground as well as an airplane when falling to earth, so could be used to detonate over the heads of the enemy on the battlefield.
This eliminated the security provided by trenches and trenches with In a normal artillery barrage, the shells exploded when they hit the ground, expending most of their energy and shrapnel upward. Troops could be protected if they were dug in, even if they were quite close to an explosion. The Japanese on many Pacific islands withstood enormous artillery bombardments for weeks. Using this method, but now with shells that could be detonated only five to 5-10 meters above the ground, troops in open trenches or foxholes will be hit by shrapnel exploding right above them. This was used by the Allies during the Battle of the Bulge.
When the Germans were using the dense forests in the area for cover during the attack, one report indicated that after an artillery barrage with close-range shells, the forest looked as if a giant scythe had cut through the treetops destroying everything. that was above 40 feet or 12 meters. and killing almost everyone under shelling on the open battlefield, the same tactic was used with synchronized artillery lines firing smaller mortars in front, then larger cannons behind and then howitzers in the rear firing staggered barrages on the artillery troops or to explode on German troops. positions at the same time, this could also be used to attack on the opposite side of a hill where enemy forces will be hidingwith similar results.
This was so terrifying that many of the Germans abandoned their positions due to the effectiveness of the air blasts above them. Bombs dropped from aircraft using proximity fuses were used against anti-aircraft batteries to great effect in demoralizing the gun crews over Italy, silencing the guns and allowing the American air force to advance unopposed as the Allies advanced through Germany from the Rhine to Berlin. Aircraft fire with proximity projectiles fell on more than 1,000 enemy aircraft. Proximity shells were also used to great effect against V1 flying bomb attacks on London on one day of the 104 V1s launched, 68 were shot down with proximity shells 14 by the RAF two by bombing balloons and cables and 16 suffered mechanical failure during Their flight after the war and during the trials that followed, the Germans as well as the Japanese revealed that they had no idea that proximity weapons were being used against them, the Germans themselves, in fact, developing a variety of different types. of proximity fuses for bombs and rockets, but few entered production and no one considered making them for projectiles that the Allies used to such advantage because they did not believe the electronics could survive the forces involved.
More than 20 million proximity fuzes were produced during the war. War The effect these fuses had on the outcome of a war in both the Pacific and Europe was one of the best kept secrets of the war until they were finally revealed several years later and the technology would go on to create guided missiles like the Sidewinder. We saw it earlier so I hope you found the video interesting and if you did, don't forget to subscribe, click the bell notification, like and share it. I would just like to thank all of our sponsors for their continued support
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