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
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