Earth Quake Bomb
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The earthquake bomb, or seismic bomb, was a concept that was invented by the British aeronautical engineer
Barnes Wallis Sir Barnes Neville Wallis (26 September 1887 – 30 October 1979) was an English engineer and inventor. He is best known for inventing the bouncing bomb used by the Royal Air Force in Operation Chastise (the "Dambusters" raid) to attack ...
early in
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
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
shockwave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
s. 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
bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...
s and
viaduct A viaduct is a specific type of bridge that consists of a series of arches, piers or columns supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct overpass across a wide ...
s. 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.


Theory and mechanism of damage

During development
Barnes Wallis Sir Barnes Neville Wallis (26 September 1887 – 30 October 1979) was an English engineer and inventor. He is best known for inventing the bouncing bomb used by the Royal Air Force in Operation Chastise (the "Dambusters" raid) to attack ...
theorised that 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 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 the anti-ship role, however, great damage could be done to the critical equipment on board a battleship by the shock wave alone.


Development

A Grand Slam bomb being handled at RAF Woodhall Spa in Lincolnshire An explosion in air does not transfer much energy into a solid, as their differing
acoustic impedance Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The International System of Units, SI unit of acoustic impeda ...
s 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 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 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 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 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 the standards at the time. Wallis' first concept was for a ten-ton bomb that would explode some underground. To achieve this, the bomb would have had to be dropped from . 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 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 A bouncing bomb is a bomb designed to bounce to a target across water in a calculated manner to avoid obstacles such as torpedo nets, and to allow both the bomb's speed on arrival at the target and the timing of its detonation to be predeterm ...
and shown its possibilities,
RAF Bomber Command RAF Bomber Command controlled the Royal Air Force's bomber forces from 1936 to 1968. Along with the United States Army Air Forces, it played the central role in the Strategic bombing during World War II#Europe, strategic bombing of Germany in W ...
were prepared to listen to his other ideas, even though they often thought them strange. The officer classes of 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 . Even from this relatively low altitude, 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 ''La Coupole'' (), also known as the ''Coupole d'Helfaut-Wizernes'' and originally codenamed ''Bauvorhaben'' 21 ('Building Project 21') or ''Schotterwerk Nordwest'' (Northwest Gravel Works), is a Second World War bunker complex in the Pas-de-Cal ...
and
Blockhaus d'Éperlecques The ''Blockhaus d'Éperlecques'' (, also referred to as "the Watten bunker" or simply "Watten") is a Second World War bunker, now part of a museum, near Saint-Omer in the northern Pas-de-Calais Departments of France, ''département'' of France, ...
, put out of action the V-3 cannon sites at Fortress of Mimoyecques, sink the
battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...
''Tirpitz'' and damage the
U-boat U-boats are Submarine#Military, naval submarines operated by Germany, including during the World War I, First and Second World Wars. The term is an Anglicization#Loanwords, anglicized form of the German word , a shortening of (), though the G ...
s' protective pens at St. Nazaire, as well as to attack many other targets which had been impossible to damage before. One of the most spectacular attacks was shortly after
D-Day The Normandy landings were the landing operations and associated airborne operations on 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during the Second World War. Codenamed Operation Neptune and often referred to as ...
, 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 Saumur () is a Communes of France, commune in the Maine-et-Loire Departments of France, department in western France. The town is located between the Loire and Thouet rivers, and is surrounded by the vineyards of Saumur itself, Chinon, Bourgu ...
which carried the line under a mountain. Twenty-five Lancasters dropped the first Tallboys on the mountain, penetrating straight through 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 T12 demolition bomb, which was designed to create an earthquake effect. Given the availability of
nuclear weapons A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission, fission (fission or atomic bomb) or a combination of fission and nuclear fusion, fusion reactions (thermonuclear weap ...
with
surface A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is ...
detonating laydown delivery, there was little or no development of conventional deep penetrating bombs until the 1991
Gulf War , combatant2 = , commander1 = , commander2 = , strength1 = Over 950,000 soldiers3,113 tanks1,800 aircraft2,200 artillery systems , page = https://www.govinfo.gov/content/pkg/GAOREPORTS-PEMD-96- ...
. 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 Eglin Air Force Base is a United States Air Force (USAF) base in the western Florida panhandle, located about southwest of Valparaiso, Florida, Valparaiso in Okaloosa County, Florida, Okaloosa County. The host unit at Eglin is the 96th Test ...
in Florida developed the GBU-28 that was used successfully by F-111Fs against a deep underground complex not far from
Baghdad Baghdad ( or ; , ) is the capital and List of largest cities of Iraq, largest city of Iraq, located along the Tigris in the central part of the country. With a population exceeding 7 million, it ranks among the List of largest cities in the A ...
just before the end of the war. The United States has developed a 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.


Effectiveness

Anglo-American bomb tests (Project Ruby) on the comparative effectiveness of large bombs against reinforced concrete structures were carried out in 1946. The tests found that case strength would have to be increased to make any of the tested bombs suitable for use against the targeted reinforced concrete structures.


See also

* Bunker buster * Compact Kinetic Energy Missile *
Kinetic energy penetrator A kinetic energy penetrator (KEP), also known as long-rod penetrator (LRP), is a type of ammunition designed to penetrate vehicle armour using a flechette-like, high- sectional density projectile. Like a bullet or kinetic energy weapon, this ty ...


References

{{authority control Anti-fortification weapons Aerial bombs World War II aerial bombs Explosive weapons Barnes Wallis English inventions