On September 15th 1940 the Luftwaffe began
a voracious campaign, targeting London. A sudden change in tactics, focusing the full
might of their air force on the most heavily populated city in Great Britain. Over the course of this brutal day, over 1100
German aircraft entered British airspace. An astonishing invasion to attack a non-strategic
civilian target, however this was all part of the Luftwaffe’s plan to gain air superiority
in British skies. Baiting British fighter planes into the sky
to face off against their German counterparts. A showdown to eliminate the royal air force
as a threat, to pave the way for a German amphibious invasion of Britain. On this first day of the infamous Blitz over
1000 aircraft on both sides tangled in the skies above London. The Luftwaffe believed the RAF were on their
last legs, but that couldn’t have been further from the truth. The Spitfires and Hurricanes, being manufactured
in astonishing numbers, out pacing the attrition of the battle, rose to meet the challenge. The pilots of the Luftwaffe, flying the BF
109, were astonished at the resistance they met. However, another number stands out to me from
this period. Over the course of this month, the 6th anti-aircraft
division, covering the Thames estuary, the main approach to London from Europe, expended
over a quarter of a million anti-aircraft rounds in its effort to protect the citizens
of London. A bewildering 1800 rounds were needed to take
down a single aircraft on this day, according to official records. These numbers are largely accepted by experts
as false, with actual rounds needed much higher. Many downed German aircraft claimed by anti-aircraft
crews were in fact shot down by fighters in the sky. The cause of these false reports and anti-aircrafts
technologies' ineffectiveness were the same. So, why was anti-aircraft technology during
the Battle of Britain so ineffective at damaging invading planes? And how did an ingenious, top secret technology,
introduced in the middle of the war change the face of the battlefield forever? At
the outbreak of the war anti-aircraft technology was, for the most part, a deterrent. A weapon that became vastly more effective
at lower altitudes, and in turn, forced enemy aircraft high above the clouds where they
themselves struggled to hit the mark. The task of accurately targeting a high flying
aircraft from the ground was an even more immense challenge. In the best case scenario anti-aircraft crews
had a direct line of sight with their target, allowing them to estimate both altitude, bearing,
and speed. This information was used to aim their barrels
to a location in front of the formation's current location. An educated guess of where they would be when
the shells arrived. To make this task even harder, allied fuses
had to be timed on the ground. Turning a dial on a mechanically timed fuze. Calculating the time it would take for the
round to reach the target in the heat of battle was difficult. These calculations needed to be incredibly
accurate, allowing the anti-aircraft rounds to explode in close proximity to their target. This variable was also subject to change as
pilots were also instructed to change their altitude and bearing randomly to make it impossible
to predict flight time and future location. This was a game of chance, and as such, relied
on an incredible volume of fire to stand a chance of damaging their target. This problem needed to be solved, and was
high on the mind of the British as they held through the brutal storm of this bombing campaign. For anti-aircraft rounds to become vastly
more effective they needed a way to detect their target. In the era of fragile vacuum tubes, building
an electronic device capable of surviving the immense 20,000 g acceleration launch out
of a gun barrel was a task that was deemed impossible. Work began on radar triggered fuzes in both
Britain and Germany before the war broke out, and both abandoned the idea completely for
gun launched projectiles, seeing no way to overcome the technical challenge of ruggedizing
the electronics, while miniaturizing them to fit into a small artillery shell fuze. However, the Americans persevered and came
up with this. The VT Fuze. With its ominous red vial of liquid at its
core serving a vital purpose. The challenge of finding a suitable power
source for this radar transmitter was another challenge facing the engineers. Early versions of the proximity fuze utilized
existing dry cell battery technology, but these came with 2 huge issues. Their charge would fade in just 2-3 months,
making long-term storage of these fuzes impossible. [1]
And secondly, the risk of having power accidentally connect to the transmitter and receiver was
far too high. A single failure point could explode an entire
ammunition stockpile. For a reminder of what that looks like, this
is not a nuclear bomb. This is the SS John Burke, an United States
ammunition transport ship that was struck by a Japanese kamikaze bomber while transporting
ammunition to the Philippines in 1944. The war in the pacific was the driving force
for the invention of the proximity fuze. The US were losing an astonishing number of
ships to Japanese aerial attacks and desperately needed a better way to defend their ships
with anti-aircraft fire. The solution the US National Defence Research
Committee came up with to solve this issue of safely powering this device was as bizarre
and unique as it was ingenious. The engineers switched to a wet cell design. This red vial contains the electrolyte of
the battery. This allowed for an ingenious work-around
for both problems. The liquid electrolyte was stored inside the
battery, separated from the solid plates of the battery inside this vial. Underneath this glass ampule lay a breaker
that contained a clever mechanism. Two levers were pushed towards the center
of the mechanism by a spring. [2] When the round began to spin at 50,000
revolutions per minute, as a result of the rifling in the gun barrel, these levers would
be forced out, which released a trigger, allowing a small explosive primer to force a spiked
plunger to break free and strike the glass ampule. Breaking it and releasing the electrolyte
into the battery. The plates of the battery were composed of
thin zinc plates coated in carbon on one side. Each layer separated by a plastic insulating
ring and each disk had holes punched into it to allow the electrolyte to flow and fill
each layer. This glass could ofcourse break with rough
handling, but the electrolyte would not fill the space between the battery plates without
the centrifugal force of the round forcing the liquid outwards into the surrounding plates. Other safety measures were incorporated to
make absolutely sure that the chances of an accidental detonation could only happen when
the round was in the air and spun at a tremendous speed. [3] Once energized this battery would provide
power to the oscillator, which generated a continuous sine wave radio current to the
transmitter. For space efficiency's sake, the antenna operated
as both a transmitter and receiver. With the currents traveling through the same
antenna, the fuze needed a way to differentiate between the signals sent and signal received. For this the engineers could turn to the doppler
effect. As the target and fuze are traveling towards
each other we can easily calculate the apparent frequency shift due to their relative velocity. Then, with some basic math, we can come up
with this equation by subtracting the reflected frequency from the actual frequency. This was called the beat note. This beat note is what the fuze uses to detonate
the round. The amplitude of this beat signal will also
grow as the round approaches the target. Providing a signal that looks something like
this with amplification. [4] The fuze was tuned to explode at the optimum
distance and angle away from the target by tailoring the radar sensitivity to match the
fragmentation pattern of these shells. When the round approached the target, the
returning radar waves would generate the necessary threshold voltage to trigger the thyratron,
a type of high speed electrical switch. It looks a lot like a vacuum tube, but it
is filled with a low pressure gas like hydrogen. When a voltage of sufficient magnitude was
passed from the amplifier to the cathode grid of the thyratron it would ionize the gas inside
and allow current to flow to the anode through its glowing cloud of ionized atoms. Completing a circuit to a capacitor that would
in turn detonate the high explosive charge in the round. Creating a cloud of shrapnel at the optimum
distance way from the target. This whole assembly, consisting of the vividly
red electrolyte capsule, the zinc-carbon battery plates, oscillator, antenna, amplified and
thyratron was then inserted into the fuze body and the cavities of the fuze were filled
with a microcrystalline wax for moisture protection, and critically, mechanical support the electronics
to keep everything in place during launch. Packaging this all in a fuse this small in
the 1940s was no easy feat. The tubes manufactured for the proximity fuze
were drastically smaller than existing conventional tubes. This of course helped immensely with resisting
the force of launch, with 20,000 gs of acceleration every extra gram of weight saving makes the
difference. With this multiplication of mass, a single
gram would weigh 20 kilograms. The engineering challenge of ensuring every
gram of mass inside this fuze was supported by a structure capable of bearing 20 kilograms
was immense. A challenge that deterred both the British
and Germans, and its success drastically changed the face of the battlefield. The impact this fuze had on the war cannot
be overstated. The atomic bomb was the punctuation mark of
this world wide war, but the statistics back the VT Fuze as THE most impactful invention
of the war. An invention that changed the narrative of
the war completely. A counter to the newly invented airplane,
causing havoc across every theater of the war. Such importance was placed on this invention
that it was classified as top secret and only approved for use in the pacific, where any
unexploded rounds would be lost to sea. [REF] Much of the manufacturing was performed
in smaller subassemblies to minimize any knowledgeable manufacturer from deducing the purpose of
the device. And for good reason. During the London blitz its estimated that
1800 rounds were needed to take down a single aircraft, but with the introduction of teh
VT fuze this number lowered to an average of 85-100 rounds. A 10-20 times increase in lethality. A jump in lethality that great is akin to
the introduction of the machine gun. This was, beyond a doubt, a game changing
invention. At the peak of their production over 250,000
of these fuzes were being manufactured a week. The VT fuze was first fired on January 4th,
1943 on board the cruiser Helena, defending itself from an aerial assault and successfully
shooting the aircraft down. This device had a devastating effect on the
aerial battles of the pacific. Japan soon began to run low on trained pilots
and a year later began the Kamikaze campaign, sending waves of untrained pilots towards
American ships in the hopes just one could get through. In May 1945 two destroyers off Okinawa found
themselves the targets of 150 kamikaze aircraft. Every single one of them was shot down. A feat that could not have been achieved without
the radio proximity fuze. Allowing the guns of these boats to fire relentlessly
with accurate fire with no pauses to fiddle with mechanical timed fuzes. Had it been available during the Battle of
Britain the battle would have been even shorter lived with the anti-aircraft guns of London
suddenly becoming an order of magnitude more effective the swarms of Luftwaffe bombers
would have stood little chance of returning home. It was finally approved for use over land
for the first time in conjunction with the Allied invasion of Normandy, a week before
Germany began bombarding Britain with the V1 Buzz Bomb. At its peak 100 V1s were launched towards
Britain, and with the help of the VT Fuze 80% of these automated missiles were shot
down. The VT Fuze also played a pivotal role in
the battle of the bulge, allowing artillery fire to explode at the perfect distance overhead,
showering the canopy of the ardennes forest with deadly shrapnel. Repelling Germany's final large scale counter
offensive of the war. Even at this stage of the war, with Germany
on the retreat, the VT fuze was a closely guarded secret. Each and every fuze needed to be tracked and
accounted for. With one story of artillery officers spending
hours searching through snow to locate lost fuzes during the battle of the bulge, only
for them to be returned to them by locals. World War 2 was defined by technological progress. When the entire world was at war and nations'
very survival was at stake, innovation was placed at the very pinnacle of national interests,
and this is the reason I find the war so fascinating. I have created two series. The logistics of d-day and the Battle of Britain
detail the innovations that helped win these critical battles. I put little focus on the military tactics
or individual soldiers on the ground. This is the view of these battles from the
perspective of an engineering nerd. The logistics of transporting tanks across
the english channel, how the giant game like board at the center of RAF command worked
during the battle of Britain, and the well the final episode of the Battle of Britain
shares the astonishing manufacturing innovations that allowed Britain to out manufacture Germany
in fighter planes and prevent aircraft attrition from effecting their ranks. If you are an engineering nerd these are the
series for you. If you want to watch these series the only
place you can find them is Nebula. The streaming platform I created with some
of my closest YouTube friends. It’s absolutely packed with fantastic engineering
content creators. Mustard has this incredible Original documentary
about the B2 bomber. City Beautiful has this fantastic original
series talking about the history of the world's best cities. And Neo made this 20 minute documentary about
the flight investigation of MH17. These are just some of the shows only available
on Nebula, AND you can get access for just 5 dollars a month, but if you sign up with
my link in the description you can get access for half that price at 2.50 a month. You get all that original content and all
our videos release early on Nebula too, so you can see them before anyone else on YouTube. We created Nebula to allow us to speak freely
without worry of the YouTubes community guidelines affecting our business. In this video I did my best to tiptoe around
certain words and imagery that could trigger demonetization, but that’s not something
I have to worry about in my world war 2 series on Nebula. Nebula is the world's largest creator streaming
service and its only growing and allowing us to fund incredible creator projects that
just would not be possible without direct funding from our viewers. So, why not sign up for just 2.50 a month
by clicking the link on screen right now to get access to incredible exclusive content
that you can have a direct hand in funding.
