The earthquake bomb , or seismic bomb , was a concept that was invented by the British aeronautical engineer Barnes Wallis early in World War II and subsequently developed and used during the war against strategic targets in Europe. A seismic bomb differs somewhat in concept from a traditional bomb, which usually explodes at or near the surface and destroys its target directly by explosive force; in contrast, a seismic bomb is dropped from high altitude to attain very high speed as it falls and upon impact, penetrates and explodes deep underground, causing massive caverns or craters known as camouflets , as well as intense shockwaves . In this way, the seismic bomb can affect targets that are too massive to be affected by a conventional bomb, as well as damage or destroy difficult targets such as bridges and viaducts .
32-569: The T-12 (also known as Cloudmaker ) earthquake bomb was developed by the United States from 1944 to 1948 and deployed until the withdrawal of the Convair B-36 Peacemaker bomber aircraft in 1958. It was one of a small class of bombs designed to attack targets invulnerable to conventional "soft" bombs, such as bunkers and viaducts . It achieved this by having an extremely thick, hardened nose section designed to penetrate deeply into
64-457: A 3.6 magnitude earthquake, destroying any nearby structures such as dams, railways, viaducts, etc. Any concrete reinforcement of the target would probably serve to enclose the force better. Wallis also argued that, if the bomb penetrated deep enough, the explosion would not breach the surface of the ground and would thus produce a cavern (a camouflet ) which would remove the structure's underground support, thus causing it to collapse. The process
96-527: A built up area causing minimal damage to the surroundings. Precision bombing was initially tried by both the Allied and Central Powers during World War I , however it was found to be ineffective because the technology did not allow for sufficient accuracy. Therefore, the air forces turned to area bombardment , which killed civilians. Since the War, the development and adoption of guided munitions has greatly increased
128-521: A detailed plan for the entire US Army Air Forces (USAAF), was drafted by four officers who had been proponents of precision bombing at the Air Corps Tactical School : Lt. Col. Harold L. George , Lt. Col. Kenneth N. Walker , Maj. Haywood S. Hansell Jr. , and Maj. Laurence S. Kuter . AWPD-1 prescribed an emphasis on precision bombing against the German national infrastructure, industry—especially
160-401: A highly aerodynamic, very heavy bomb with a delayed detonation would cause damage to a target through shock waves travelling through the ground, hence the nickname earthquake bombs. The airmen who dropped the bombs reported that the target structures stood undamaged by the detonation; "But then the crater collapsed, the ground shifted and the target collapsed". Later computer simulations reached
192-703: The Pathfinder Force . Specialist units such as 617 squadron were able to use these and other techniques to achieve remarkable precision, such as the bombing of the Michelin factory at Clermont-Ferrand in France, where they were required to destroy the workshops but leave the canteen next to them standing. By 1941, precision day bombing had become the dominant doctrine in the US Army Air Corps . As war with Germany loomed, Air War Plans Division Plan No. 1 (AWPD-1),
224-448: The " Victory Bomber ", but there was no support for an aircraft with only a single purpose. Wallis then took a different line in developing a means to destroy Germany's industrial structure with attacks on its supply of hydroelectric power. After he had developed the bouncing bomb and shown its possibilities, RAF Bomber Command were prepared to listen to his other ideas, even though they often thought them strange. The officer classes of
256-481: The ' Battle of the Beams ' The RAF later developed their own beam guidance techniques, such as GEE and Oboe . These systems could provide an accuracy of about 100 yards radius, and were supplemented by the downward-looking radar system H2S . The British development of specialist 'Earthquake' bombs (which needed to be dropped very accurately) led to the development of supporting aiming techniques such as SABS and
288-500: The 5,000-pound (2,300 kg) GBU-28 that was used successfully by F-111Fs against a deep underground complex not far from Baghdad just before the end of the war. The United States has developed a 30,000-pound (14,000 kg) Massive Ordnance Penetrator , designed to attack very deeply buried targets without the use of nuclear weapons with the inherent huge levels of radioactive pollution and their attendant risk of retaliation in kind. Anglo-American bomb tests (Project Ruby) on
320-562: The M110, but incorporated modifications based on testing and calculations. The B-36 was redesigned so it could carry the T-12, although a converted B-29 Superfortress was used for testing. Earthquake bomb Earthquake bombs were used towards the end of World War II on massively reinforced installations, such as submarine pens with concrete walls several meters thick, caverns, tunnels, and bridges. During development Barnes Wallis theorised that
352-510: The RAF at that time were often trained not in science or engineering, but in the classics , Roman and Greek history and language. They provided enough support to let him continue his research. Later in the war, Barnes Wallis made bombs based on the "earthquake bomb concept", such as the 6-ton Tallboy and then the 10-ton Grand Slam , although these were never dropped from more than about 25,000 feet (7.6 km). Even from this relatively low altitude,
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#1732844066829384-529: The accuracy of aerial bombing. Because the accuracy achieved in bombing is dependent on the available technology, the "precision" of precision bombing is relative to the time period. Precision has always been recognized as an important attribute of weapon development. The noted military theorist, strategist, and historian Major-General J. F. C. Fuller , considered "accuracy of aim" one of the five recognizable attributes of weaponry, together with range of action, striking power, volume of fire, and portability. In
416-644: The aircraft industry—and the Luftwaffe. For the USAAF, daylight bombing was normal based upon box formations for defense from fighters. Bombing was coordinated through a lead aircraft but although still nominally precision bombing (as opposed to the area bombing carried out by RAF Bomber Command ) the result of bombing from high level was still spread over an area. Before the war on practice ranges, some USAAF crews were able to produce very accurate results, but over Europe with weather and German fighters and anti-aircraft guns and
448-481: The anti-shipping role, however, great damage could be done to the critical equipment on board a battleship by the shock wave alone. An explosion in air does not transfer much energy into a solid, as their differing acoustic impedances makes an impedance mismatch that reflects most of the energy. Due to the lack of accuracy of bombing in the face of anti-aircraft defences, air forces used area bombardment , dropping large numbers of bombs so that it would be likely that
480-437: The bombers a better chance of survival, but made it much harder to even find the general area of the target, let alone drop bombs precisely. The Luftwaffe addressed this issue first by using a series of radio beams to direct aircraft and indicate when to drop bombs. Several different techniques were tried, including Knickebein, X-Gerät and Y-Gerät (Wotan). These provided impressive accuracy—British post-raid analysis showed that
512-407: The comparative effectiveness of large bombs against reinforced concrete structures were carried out in 1946. Precision bombing Precision bombing is the attempted aerial bombing of a target with some degree of accuracy, with the aim of maximising target damage or limiting collateral damage . Its strategic counterpart is carpet bombing . An example would be destroying a single building in
544-550: The early days of World War II , bombers were expected to strike by daylight and deliver accurately in order to avoid civilian casualties. Cloud cover and industrial haze frequently obscured targets so bomb release was made by dead reckoning from the last navigational "fix"—the bombers dropping their loads according to the ETA for the target. Some airforces soon found that daylight bombing resulted in heavy losses since fighter interception became easy and switched to night bombing. This allowed
576-559: The earth before exploding and then damage the target by the resulting shock wave. The T-12 was a further development of the concept initiated with the United Kingdom's Tallboy and Grand Slam weapons developed by British aeronautical engineer Barnes Wallis during the Second World War : a hardened, highly aerodynamic bomb of the greatest possible weight designed to be dropped from the highest possible altitude. Penetrating deeply in
608-451: The earth before exploding, the resulting shock wave was transmitted through the earth into targets. The resulting underground cavity and ground motion could also undermine structures. The bomb could also be used against hardened targets. These types of bombs can reach supersonic speeds and have tail fins designed to spin the bomb for greater accuracy. Originally designed to meet a 42,000 lb (19,000 kg) target weight (one half of
640-591: The earthquake bomb had the ability to disrupt German industry while causing minimum civilian casualties. It was used to disable the V2 launch sites at La Coupole and Blockhaus d'Éperlecques , put out of action the V-3 cannon sites at Fortress of Mimoyecques , sink the battleship Tirpitz and damage the U-boats ' protective pens at St. Nazaire , as well as to attack many other targets which had been impossible to damage before. One of
672-477: The limited training for new crews this level of accuracy was impossible to reproduce. The US defined the target area as being a 1,000 ft (300 m) radius circle around the target point - for the majority of USAAF attacks only about 20% of the bombs dropped struck in this area. The U.S. daytime bombing raids were more effective in reducing German defences by engaging the German Luftwaffe than destruction of
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#1732844066829704-581: The maximum payload for the Convair B-36 "Peacemaker" bomber), with its hardened case was slightly less than 43,000 lb (19,500 kg). The final T-12 weighed 43,600 lb (19,800 kg). This was twice the size of the United States' previous largest bomb, the 22,000 lb (10,000 kg) M110 (T-14), the American-built version of the British Grand Slam. The T-12 was not a simple scale up of
736-629: The means of aircraft production. An example of the difficulties of precision bombing was a raid in the Northern Hemisphere summer of 1944 by 47 B-29 's on Japan's Yawata Steel Works from bases in China. Only one plane actually hit the target area, and only with one of its bombs. This single 500 lb (230 kg) general-purpose bomb represented one quarter of one percent of the 376 bombs dropped over Yawata on that mission. It took 108 B-17 bombers, crewed by 1,080 airmen, dropping 648 bombs to guarantee
768-459: The most spectacular attacks was shortly after D-Day , when the Tallboy was used to prevent German tank reinforcements from moving by train. Rather than blow up the tracks – which would have been repaired in a day or so – the bombs were targeted on a tunnel near Saumur which carried the line under a mountain. Twenty-five Lancasters dropped the first Tallboys on the mountain, penetrating straight through
800-433: The rock, and one of them exploded in the tunnel below. As a result, the entire rail line remained unusable until the end of the war. The Bielefeld viaduct was only closed for brief periods by 54 raids dropping 3,500 tons; but in its first use on 14 March 1945 the "Grand Slam" destroyed whole sections of the viaduct. After World War II, the United States developed the 43,000-pound (20,000 kg) T12 demolition bomb, which
832-501: The same conclusions; the significant part of the damage was done by generating a cavity in the ground. That cavity collapsing caused the ground to shift, hence the target's foundation to shift or break causing catastrophic structural damage to the target. The shifting ground caused any larger structure to become severely damaged, even if the bomb missed the target but created a crater near it. They were not true seismic weapons, but effective cratering weapons when used on ground targets. In
864-399: The standards at the time. Wallis' first concept was for a ten-ton bomb that would explode some 130 feet (40 m) underground. To achieve this, the bomb would have had to be dropped from 40,000 feet (12 km). The RAF had no aircraft at the time capable of carrying a ten-ton bomb load aloft, let alone lifting it to such a height. Wallis designed a six-engine aeroplane for the task, called
896-415: The target would be hit. Although a direct hit from a light bomb would destroy an unprotected target, it was comparatively easy to armour ground targets with many yards of concrete, and thus render critical installations such as bunkers essentially bombproof. If the bomb could be designed to explode in water, soil, or other less compressible materials, the explosive force would be transmitted more efficiently to
928-420: The target. Barnes Wallis' idea was to drop a large, heavy bomb with a hard armoured tip at supersonic speed (as fast as an artillery shell) so that it penetrated the ground like a ten-ton bullet being fired straight down. It was then set to explode underground, ideally to the side of, or underneath, a hardened target. The resulting shock wave from the explosion would then produce force equivalent to that of
960-459: The vast majority of the bombs dropped could be placed within 100 yards (91 m) of the midline of the beam, spread along it a few hundred yards around the target point, even in pitch-dark conditions at a range of several hundred miles. But the systems fatally depended on accurate radio reception, and the British invented the first electronic warfare techniques to successfully counter this weapon in
992-666: Was designed to create an earthquake effect. Given the availability of nuclear weapons with surface detonating laydown delivery , there was little or no development of conventional deep penetrating bombs until the 1991 Gulf War . During the Gulf War, the need for a conventional deep penetrator became clear. In three weeks, a cooperative effort directed by the Armament Systems Division at Eglin Air Force Base in Florida developed
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1024-491: Was graphically described as a "trapdoor effect" or "hangman's drop". Wallis foresaw that disrupting German industry would remove its ability to fight, and also understood that precision bombing was virtually impossible in the late 1930s. The technology for precision aiming was developed during World War II, and Barnes Wallis' ideas were then shown to be successful (see for example the Bielefeld raid on 14 March 1945), considering
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