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  • This episode of Real Engineering is brought to you by Brilliant, a problem solving website

  • that teaches you to think like an engineer.

  • If we were to define WW2 in just one technology, the likely winner would be aerial bombing.

  • World War 1 revolved around stagnant and debilitating trench warfare, that both sides sought to

  • avoid in future.

  • Tanks and planes arose as a way of breaking enemy lines quickly and inflict damage.

  • The rate of technological progress for delivering larger and more accurate bombs during world

  • war 2 was astronomical, but early in the war the technology was still in its infancy.

  • The Germans relied heavily on the Stuka dive bomber.

  • A short range bomber whos siren became a harbinger of death on the battlefield.

  • It dived towards its target, planting it firmly in its crosshairs, imparting its bomb with

  • the velocity it need to fly straight to the target, before releasing and pulling up hard

  • to avoid a collision with the ground.

  • This procedure was so taxing on its pilot that the Germans developed an automatic dive-flap

  • that would deploy even if the pilot had knock themselves unconscious with g-force.

  • These tactics arose because bombing aiming technology was so primitive, bomb sights were

  • rudimentary and required skilled operators.

  • Having to factor not only the speed and altitude of the aircraft, but the terminal velocity

  • of the bomb and how it would be affected by wind as it fell.

  • Bombing from high altitude, where the bombers would be relatively safe from Flak, gave little

  • precision to target specific buildings.

  • This combined with poor navigation equipment resulted in both sides devolving into carpet

  • bombing, causing massive loss of life to civilian life, which did little to help either side

  • win a war.

  • We saw in a previous episode how much effort Nazi cities put into anti-aircraft defences,

  • and similar efforts were made in Britain.

  • These tactics did not come cheap, losses were high for both sides..

  • Barnes Wallis, an Aeronautical Engineer at Vickers, saw the futility in these tactics

  • and set his focus on developing new technologies to aid British bombers in destroying strategic

  • German positions.

  • This was nothing new.

  • Factories, oil storage and transportation infrastructure were always primary targets,

  • but Barnes wanted to create a weapon capable of destroying a target others deemed invulnerable.

  • Dams.

  • Dams posed a tantalizing target.

  • They supply hydroelectricity, provided water for industry and the German population, and

  • the resulting deluge of water from the massive reservoirs would cause damage much greater

  • than any bomb the Brit's had at their disposal.

  • The Germans were not ignorant to the allure the dams as a bombing target.

  • Attacks on dams had happened earlier in the war, like the attack on the massive Italian

  • Tirso dam in Sardinia, which held back Europe's largest man-made lake and provided the Italian

  • island with a third of its electricity.

  • They attempted the raid in broad daylight with 8 Swordfish floatplanes.

  • 3 simply failed to find the target due to terrible weather, and the rest were welcomed

  • with anti-aircraft fire, taking one of the planes down.

  • The remaining 4 continued to the target and dropped torpedoes which travelled underwater

  • to their target before exploding, but the dam remained standing.

  • The bombs were simply not powerful enough to blast through the heavy concrete of the

  • dam.

  • To make matters worse, all dams across Europe would be protected by anti-torpedo netting

  • from this point on.

  • So a new method to deliver an enormous bomb capable of taking down a structure this strong

  • was needed.

  • Wallis spent most of his time devising devices to take on challenges like this, and took

  • several things into consideration when designing his bombs.

  • Explosive pressures decay extremely quickly, and thus to ensure damage to the structure

  • it must be as close as possible, pressure waves propagate through denser mediums far

  • more efficiently, and thus explosions underground or in water will be more powerful.

  • And finally, doubling the size of the bomb does not result in twice the blast radius,

  • to increase the blast radius drastically would require a drastically larger bomb.

  • His design ethos from here was simply.

  • Design the biggest bomb his planes could carry, and have them detonate underground or in water

  • to maximise their effect even further.

  • He presented his ideas in a 1941 paper “A Note on a Method of Attacking the Axis Powers

  • with the primary focus on a 10 tonne earth penetrating bomb, that would be dropped from

  • 40,000 feet, this was the most powerful non-nuclear bomb ever used until just last year, and 42

  • were dropped in the final year of the war that helped cut German supplies to the front

  • line, by destroying viaducts and railways.

  • But Wallis is remembered for a different bomb.

  • The British government hired the Road Research Laboratory, a civil engineering firm, to begin

  • experiments to find the smallest charge needed to destroy the Mohne Dam.

  • They constructed several scale model dams, and used abandoned dams in Wales to find their

  • answer.

  • They found that even a 10 tonne bomb exploding 50 feet from the dam would not destroy it,

  • but a 2 tonne bomb could do the job if it was placed directly next to the face of the

  • dam.

  • With torpedo netting installed, this job required precision that had not been seen before, and

  • the method that was devised would break all convention.

  • Barnes decided the best course of action was to create a skipping bomb, that would bounce

  • over the protective netting before sinking next to the dam and exploding.

  • He concluded that the mines would have to impact at less than 7 degrees in order to

  • skipp, and all subsequent bounces would also have to be below 7 degrees to ensure the bomb

  • continued until momentum was lost.

  • The bomb would be given a backspin prior to release in order to take advantage of the

  • Magnus effect, which is lift created by a spinning body.

  • Spinning the bomb provided it stability, like a bicycle wheel in motion.

  • Helping the bomb remain on a straight trajectory, but the lift the spinning provided was far

  • more useful.

  • By adding lift the bomb's trajectory gained more horizontal motion, and it's angle of

  • impact was reduced.

  • Both of which aid skipping, and allowed the bomber to release the bomb sooner, giving

  • them additional time to escape the imminent explosion.

  • Once submerged the remaining spin would then help push the bomb forward ensuring it stayed

  • in close contact to the dam wall.

  • This wholly unconventional bomb posed some design challenges.

  • Any spinning object needs to be precisely balanced to prevent vibrations that could

  • potential break it, or interfere with it's operation.

  • To aid this, Barnes early spherical designs were scrapped in favour of a drum which could

  • be more easily manufactured and balanced, while also aiding with it's release mechanism.

  • The bombs were fitting to Avro Lancasters, which were modified to accommodate the bomb

  • . The bomb doors were removed to fit bomb, which would protrude below the plane for the

  • duration of the flight.

  • The lower ventral guns were removed to reduce drag, as the mission would be flown so low

  • to the ground that they would provide no protection against fighters.

  • Two v-shaped mounting arms were then attached with free-spinning disc mounts which would

  • mate with the support rings on either side of the bomb.

  • An off the shelf motor, typically used to power hydraulic pumps on submarines was used,

  • and connected to the bomb with a pulley.

  • Finally, to release the bomb Barnes needed some way of unmating bomb from it's spinning

  • mount.

  • This was done rather ingeniously.

  • These mounting arms were stabilised with a tensioned wire, which kept them firmly mated

  • with the bomb.

  • When the bomb needed to be released, the tension was released with a solenoid actuated grip.

  • Compressed springs would then force the arms to swing outwards by just a couple of degrees,

  • enough to release the bomb

  • The bomb was now ready, but little time was afforded to the crew that would man the planes

  • that would carry them.

  • A new special squadron was created specifically for this mission, formed by some of the most

  • experienced pilots the RAF had to offer.

  • This experience would be needed, as the entire mission would be flown at extremely low altitude

  • at night.

  • Navigators had to learn to navigate with limited information, often little more than the bomb

  • aimers calling out landmarks they passed over.

  • To increase the time they had to train, their Lancasters were fitted with blue plastic screens

  • to the windows to limit visibility and light during the day.

  • After many test drops the crew were finally informed of their target on the morning of

  • the attack on May 16th.

  • That night they would take off from RAF Scampton in 3 waves with a total of 19 aircraft.

  • Little would go smoothly from here.

  • The first of the planes was lost just an hour into the mission, when it strayed off course

  • over the heavily defended Texal Island off the Northern coast of the Netherlands.

  • Two planes collided with power lines and cables as they flew low over the dutch and german

  • countryside.

  • Another plane flew so low as it crossed the North Sea, that the low slung bomb collided

  • with a wave, dislodging it and forcing it's crew to return to base, followed shortly after

  • by another plane badly damaged by Flak.

  • At this point the entire first wave of planes had failed their mission, but others were

  • finally reaching their target.

  • Gibson, the commander of the squadron, was the first to arrive flying at 370 km/h just

  • 60 ft from the water, he successfully dropped his bomb which bounced three times before

  • sinking and exploding, sending a gigantic spout of water above the dam, but it had sunk

  • too short of the dam.

  • On the following run a bomb bounced over the dam and destroyed the powerhouse at its base,

  • while the Lancaster that carried it crashed into flames after being struck by flak.

  • Gibson at this point circled back around to act as a decoy, for Henry Young whos bomb

  • veered off towards the banks of the reservoir.

  • On the fourth try the squadron finally got a direct hit, but another blow was needed

  • to collapse the dam, which came shortly after as Gibson and Micky Martin flew decoy runs

  • alongside Maltby who scored a direct hit on the already crumbling dam, sending 330 million

  • tonnes of water into the valleys below.

  • With their first target down, the 1st wave continued on to Eder dam with 3 bombs left,

  • which was all they needed.

  • After two unsuccessful attempts, where one bomb damaged the plane that was dropping it,

  • Knight's Lancaster came in at the perfect speed and altitude, releasing his bomb before

  • quickly pulling hard to avoid the 300 ft hill directly behind the dam.

  • The first wave were now out of bombs and made their journey home, but this leg was just

  • as dangerous, as the already damaged plane was shot down soon after.

  • 2 more lancasters would also be brought down by flak on their return leg

  • The third wave lost two planes before reaching their newly assigned target.

  • One strayed over the city of Hamm and was gunned down by anti-aircraft guns, another

  • was lost over the Netherlands.

  • What remained mounted an unsuccessful attack on the Sorpe dam, before returning to base.

  • In all the British lost 8 Lancasters in the raid, killing 53 men, while another 3 who

  • managed to survive their crashes were taken prisoner.

  • But the damage inflicted on the Germans was far greater.

  • The resulting floods wreaked havoc on the Ruhr valley, every bridge downstream for 45

  • kilometres was destroyed.

  • 10 factories were destroyed and a further 100 were damaged.

  • Mines were flooded, and an estimated 400,000 tonnes of coal production was lost.

  • Acres of farmland were wiped out, and over 1500 people died in the resulting floods.

  • All this damage with just 19 aircraft, this was precision that had not been seen before.

  • However, some have questioned whether the raids were worth this loss in life.

  • Many of the people killed in the floods were prisoners of war in forced labour, and others

  • are quick to dismiss this raid as a failure, because the Germans recovered so quickly.

  • Taking just 5 months to repair the dams, in time to ensure the reservoirs would fill for

  • the following summer.

  • But these people seem to ignore the immense amount of resources that had to be diverted

  • to repair the dams.

  • They were repaired quickly precisely because they were so vital to the German war effort,

  • that it was worth shifting thousands of works and materials away from the front lines.

  • D-Day, which would come just a year after this raid, could have gone very differently

  • if those resources had instead gone on to fortify the beaches of France even further.

  • These 19 bombers, pound for pound, did more damage to the German war effort than any other

  • British air raid thanks to the precision they had been engineered to achieve, and precision

  • would become the focus of many of the wars greatest engineers once the war had ended,

  • after all the Moon was much further away than any previous target.

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Britain's Most Daring WW2 Raid

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    joey joey に公開 2021 年 06 月 01 日
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