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Rope trick is the term given by American nuclear physicist John Malik to the curious lines and spikes which emanate from the fireball of nuclear explosions under certain conditions, just after detonation. [1] [2]
The adjacent photograph shows two unusual phenomena: bright spikes projecting from the bottom of the fireball, and the peculiar mottling of the expanding fireball surface.
The surface of the fireball, with a temperature over 20,000 Kelvin, emits huge amounts of visible light radiation, more than 100 times the intensity at the Sun's surface. Anything solid in the area absorbs the light and rapidly heats. The "rope tricks" that protrude from the bottom of the fireball are caused by the heating, rapid vaporization and then expansion of guy wires that extend from the shot cab—the housing at the top of the bomb tower that contains the explosive device—to the ground. Malik observed that when the guy wires were painted black, spike formation was enhanced, and if it were painted with reflective paint or wrapped in aluminium foil, no spikes were observed – thus confirming the hypothesis that it is heating and vaporization of the rope, induced by exposure to high-intensity visible light radiation, which causes the effect. Because of the lack of guy wires, no "rope trick" effects were observed in surface-detonation tests, free-flying weapons tests, or underground tests. [1]
The cause of a surface mottling is more complex. In the initial microseconds after the explosion, a fireball is formed around the bomb by the massive numbers of thermal x-rays released by the explosion process. These x-rays cannot travel very far in standard atmosphere before reacting with molecules in the air, so the result is a fireball that rapidly forms within about 10 metres (33 ft) in diameter and does not expand. This is known as a "radiatively driven" fireball.[ citation needed ]
Inside the radiative fireball, the bomb itself is rapidly expanding due to the heat generated by the nuclear reactions. This moves outward at supersonic speeds, creating a hydrodynamic shock wave at its outer edge. After a brief period, this shock front reaches and then passes the initial radiative fireball. The shock wave contains so much energy that the compression heating created in the air causes it to glow. At the point in the explosion captured in the adjacent photo, the shock front has passed the original radiative fireball and has about twice its size.[ citation needed ]
In the first few microseconds after detonation, the bomb casing and shot cab are destroyed and vaporized. These vapors are accelerated to very high velocities, several tens of kilometers per second, faster than the shock front. However, this acceleration happens in a short period, so the material is trapped behind the shock front, even though it eventually travels faster than the shock front. The various light and dark patches are caused by the varying vapor density of the material splashing against the back of the shock front. The irregular variations in mass distribution around the bomb core create the mottled blob-like appearance. [3]
After a few milliseconds, the energy of the shock front will no longer be great enough to heat the air into incandescence. At that point, the shock front becomes invisible, a process known as "breakaway". This makes the shock wave difficult to diagnose beyond this boundary.
Photographs of nuclear tests often show numerous vertical rope-like lines to one side. These are typically created by small sounding rockets launched a few seconds before the firing, leaving smoke trails. The purpose of these trails is to record the passing of the now invisible shock wave, which causes an obvious visual effect on the smoke by compressing the air into a lens. This is not necessarily related to the rope trick effect in any physical way, but it is possible to confuse the two in some photographs. In the photograph of the Tumbler-Snapper test, the vertical lines in the lower-right corner are blast line poles not smoke trails. [4]
The photo was shot by a rapatronic camera (a high-speed camera invented by Harold Edgerton and colleagues) built by EG&G. [5] Each camera was capable of recording only one exposure on a single sheet of film. To create time-lapse sequences, banks of four to ten cameras were set up to take photos in rapid succession. The average exposure time was three microseconds.
Little Boy is the name of the type of atomic bomb used in the bombing of the Japanese city of Hiroshima on 6 August 1945 during World War II, making it the first nuclear weapon used in warfare. The bomb was dropped from the Boeing B-29 Superfortress Enola Gay piloted by Colonel Paul W. Tibbets Jr., commander of the 509th Composite Group, and Captain Robert A. Lewis. It exploded with an energy of approximately 15 kilotons of TNT (63 TJ) and had an explosion radius of approximately 1.3 kilometers which caused widespread death across the city. The Hiroshima bombing was the second nuclear explosion in history, after the Trinity nuclear test.
A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechanical stress, the impact and penetration of pressure-driven projectiles, pressure damage, and explosion-generated effects. Bombs have been utilized since the 11th century starting in East Asia.
Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
Operation Ivy was the eighth series of American nuclear tests, coming after Tumbler-Snapper and before Upshot–Knothole. The two explosions were staged in late 1952 at Enewetak Atoll in the Pacific Proving Ground in the Marshall Islands.
The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories:
A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke, and usually condensed water vapour resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently energetic detonation or deflagration will produce a similar effect. They can be caused by powerful conventional weapons, including thermobaric weapons such as the ATBIP and GBU-43/B MOAB. Some volcanic eruptions and impact events can produce natural mushroom clouds.
Project Orion was a study conducted in the 1950s and 1960s by the United States Air Force, DARPA, and NASA into the viability of a nuclear pulse spaceship that would be directly propelled by a series of atomic explosions behind the craft. Early versions of the vehicle were proposed to take off from the ground; later versions were presented for use only in space. The design effort took place at General Atomics in San Diego, and supporters included Wernher von Braun, who issued a white paper advocating the idea. Non-nuclear tests were conducted with models, but the project was eventually abandoned for several reasons, including the 1963 Partial Test Ban Treaty, which banned nuclear explosions in space, amid concerns over nuclear fallout.
The exploding-bridgewire detonator is a type of detonator used to initiate the detonation reaction in explosive materials, similar to a blasting cap because it is fired using an electric current. EBWs use a different physical mechanism than blasting caps, using more electricity delivered much more rapidly. They explode with more precise timing after the electric current is applied by the process of exploding wire. The precise timing exploding wire detonators compared with other types of detonators has led to their common use in nuclear weapons.
"Duck and cover" is a method of personal protection against the effects of a nuclear explosion. Ducking and covering is useful in offering a degree of protection to personnel located outside the radius of the nuclear fireball but still within sufficient range of the nuclear explosion that standing upright and uncovered is likely to cause serious injury or death. In the most literal interpretation, the focus of the maneuver is primarily on protective actions one can take during the first few crucial seconds-to-minutes after the event, while the film of the same name and a full encompassing of the advice also cater to providing protection up to weeks after the event.
Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in Enewetak Atoll, in the now independent island nation of the Marshall Islands, as part of Operation Ivy. It was the first full test of the Teller–Ulam design, a staged fusion device.
Elugelab, or Elugelap, was an island, part of the Enewetak Atoll in the Marshall Islands. It was destroyed in the world's first full-scale thermonuclear explosion, the Mike shot of Operation Ivy, on November 1, 1952. Prior to being destroyed, the island was described as "just another small naked island of the atoll".
A bhangmeter is a non-imaging radiometer installed on reconnaissance and navigation satellites to detect atmospheric nuclear detonations and determine the yield of the nuclear weapon. They are also installed on some armored fighting vehicles, in particular NBC reconnaissance vehicles, in order to help detect, localise and analyse tactical nuclear detonations. They are often used alongside pressure and sound sensors in this role in addition to standard radiation sensors. Some nuclear bunkers and military facilities may also be equipped with such sensors alongside seismic event detectors.
The rapatronic camera is a high-speed camera capable of recording a still image with an exposure time as brief as 10 nanoseconds.
The explosive yield of a nuclear weapon is the amount of energy released such as blast, thermal, and nuclear radiation, when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produce the same energy discharge), either in kilotonnes (kt—thousands of tonnes of TNT), in megatonnes (Mt—millions of tonnes of TNT), or sometimes in terajoules (TJ). An explosive yield of one terajoule is equal to 0.239 kilotonnes of TNT. Because the accuracy of any measurement of the energy released by TNT has always been problematic, the conventional definition is that one kilotonne of TNT is held simply to be equivalent to 1012 calories.
Operation Tumbler–Snapper was a series of nuclear weapons tests conducted by the United States in early 1952 at the Nevada Test Site. The Tumbler–Snapper series of tests followed Operation Buster–Jangle and preceded Operation Ivy.
An underwater explosion is a chemical or nuclear explosion that occurs under the surface of a body of water. While useful in anti-ship and submarine warfare, underwater bombs are not as effective against coastal facilities.
Argon flash, also known as argon bomb, argon flash bomb, argon candle, and argon light source, is a single-use source of very short and extremely bright flashes of light. The light is generated by a shock wave in argon or, less commonly, another noble gas. The shock wave is usually produced by an explosion. Argon flash devices are almost exclusively used for photographing explosions and shock waves.
An explosion is a rapid expansion in volume of a given amount of matter associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Explosions may also be generated by a slower expansion that would normally not be forceful, but is not allowed to expand, so that when whatever is containing the expansion is broken by the pressure that builds as the matter inside tries to expand, the matter expands forcefully. An example of this is a volcanic eruption created by the expansion of magma in a magma chamber as it rises to the surface. Supersonic explosions created by high explosives are known as detonations and travel through shock waves. Subsonic explosions are created by low explosives through a slower combustion process known as deflagration.
A transient condensation cloud, also called a Wilson cloud, is observable surrounding large explosions in humid air.
Nuclear blackout, also known as fireball blackout or radar blackout, is an effect caused by explosions of nuclear weapons that disturbs radio communications and causes radar systems to be blacked out or heavily refracted so they can no longer be used for accurate tracking and guidance. Within the atmosphere, the effect is caused by the large volume of ionized air created by the energy of the explosion, while above the atmosphere it is due to the action of high-energy beta particles released from the decaying bomb debris. At high altitudes, the effect can spread over large areas, hundreds of kilometers. The effect slowly fades as the fireball dissipates.
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