字幕列表 影片播放 列印英文字幕 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. Once again, for this kind of topic a smooth segue isn't appropriate, but videos like this would not be possible without Brilliant. My goal for this project has always been to inspire the next generation of engineers. Brilliant is the perfect partner for this channel because their courses are designed to educate you from knowing nothing to having a deep understanding of a topic. Perhaps you feel like you could brush up on your statistics skills, a valuable analytical tool that help you academically and in your everyday life. This course on statistics guides you through problems that are broken into digestible sections with fun problems to test your knowledge along the way, allowing you to see the pattern in complicated data. This is just one of many courses on Brilliant, with more courses due to released soon on things like automotive engineering and Python Coding. If I have inspired you and you want to educate yourself, then go to brilliant.org/RealEngineering and sign up for free.And the first 73 people that go to that link will get 20% off the annual Premium subscription. As always thanks for watching and thank you to all my Patreon supporters. If you would like to see more from me the links to my instagram, twitter, subreddit and discord server are below.