Explosion- fast physical or physicochemical process, passing with a significant release of energy in a small volume in a short period of time and leading to shock, vibration and thermal effects on the environment due to the high-speed expansion of the explosion products.

Deflagration explosion- energy release in the volume of a cloud of combustible gaseous mixtures and aerosols during the propagation of an exothermic chemical reaction at a subsonic speed.

Detonation explosion- explosion, in which the ignition of subsequent layers of explosive occurs as a result of compression and heating by a shock wave, characterized by the fact that the shock wave and the chemical reaction zone follow each other inseparably at a constant supersonic speed.

The chemical explosion of non-condensed substances differs from combustion in that combustion occurs when a combustible mixture is formed in the process of combustion itself. : 36

Explosion products are usually gases with high pressure and temperature, which, when expanding, are capable of performing mechanical work and causing destruction of other objects. In addition to gases, explosion products can also contain highly dispersed solid particles. The destructive effect of an explosion is caused by high pressure and the formation of a shock wave. Explosion effects can be amplified by cumulative effects.

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  The following types of explosions are distinguished by the origin of the released energy:

  • Chemical explosions explosives- due to energy chemical bonds starting materials.
  • Explosions of containers under pressure (gas cylinders, steam boilers, pipelines) - due to the energy of compressed gas or superheated liquid. These include, in particular:
    • Explosion of expanding vapors of a boiling liquid (BLEVE).
    • Explosions on depressurization in superheated liquids.
    • Explosions when two liquids are mixed, the temperature of one of which is much higher than the boiling point of the other.
  • Nuclear explosions - due to the energy released in nuclear reactions.
  • Electrical explosions (for example, during a thunderstorm).
  • Volcanic explosions.
  • Explosions in the collision of cosmic bodies, for example, in the fall of meteorites on the surface of the planet.
  • Explosions caused by gravitational collapse (supernova explosions, etc.).

  Chemical explosions

  Unanimous opinion about which chemical processes should be considered an explosion, does not exist. This is due to the fact that high-speed processes can proceed in the form of detonation or deflagration (slow combustion). Detonation differs from combustion in that chemical reactions and the process of energy release proceed with the formation of a shock wave in the reacting substance, and the involvement of new portions of an explosive in a chemical reaction occurs at the front of the shock wave, and not through heat conduction and diffusion, as in slow combustion. The difference in the mechanisms of energy and substance transfer affects the rate of the processes and the results of their action on the environment, however, in practice, a variety of combinations of these processes and transitions of combustion to detonation and vice versa are observed. In this regard, various fast processes are usually referred to chemical explosions without specifying their nature.

  There is a more rigid approach to defining a chemical explosion as exclusively detonation. From this condition, it necessarily follows that in a chemical explosion accompanied by a redox reaction (combustion), the combusting substance and the oxidant must be mixed, otherwise the reaction rate will be limited by the rate of the oxidant delivery process, and this process, as a rule, has a diffusional character. For example, natural gas burns slowly in home stove burners as oxygen slowly enters the combustion area by diffusion. However, if you mix gas with air, it will explode from a small spark - a volumetric explosion. There are very few examples of chemical explosions that do not cause oxidation / reduction, for example, the reaction of finely dispersed phosphorus (V) oxide with water, but it can also be considered a steam explosion.

  Individual explosives usually contain oxygen in their own molecules. These are metastable substances that can be stored for a more or less long time under normal conditions. However, when an explosion is initiated, sufficient energy is transferred to the substance for spontaneous propagation of a combustion or detonation wave that captures the entire mass of the substance. Nitroglycerin, trinitrotoluene and other substances have similar properties.

  What is an explosion? This is a process of instantaneous transformation of the state in which a significant amount of thermal energy and gases are released, forming a shock wave.

  Explosives are compounds that have the ability to undergo changes in physical and chemical state as a result of external influences with the formation of an explosion.

  Explosion classification

  1. Physical - the energy of an explosion is the potential energy of a compressed gas or vapor. Depending on the magnitude of the internal pressure of energy, an explosion of different power is obtained. The mechanical effect of the explosion is due to the action of the shock wave. The fragments of the shell cause an additional damaging effect.

  2. Chemical - in this case, the explosion is caused by an almost instantaneous chemical interaction of the substances that make up the composition, with the release of a large amount of heat, as well as gases and steam with high degree compression. Explosions of this type are characteristic, for example, of gunpowder. Substances arising as a result of a chemical reaction acquire great pressure when heated. The explosion of pyrotechnics also belongs to this type.

  

  3. Atomic explosions are lightning-fast reactions of nuclear fission or fusion, characterized by the enormous power of the released energy, including heat. The colossal temperature at the epicenter of the explosion leads to the formation of a zone of very high pressure. The expansion of the gas leads to the appearance of a shock wave, which is the cause of mechanical damage.

  

  The concept and classification of explosions makes it possible to act correctly in an emergency.

  Action type

  Distinctive features

  Explosions differ depending on the chemical reactions:

  1. Decomposition is typical for a gaseous medium.
  2. Redox processes imply the presence of a reducing agent with which oxygen in the air will react.
  3. Reaction of mixtures.

  Volumetric explosions include dust explosions, as well as explosions of vapor clouds.

  Dust explosions

  They are typical for closed dusty structures, such as mines. A dangerous concentration of explosive dust appears when carrying out mechanical work with bulk materials that give a large amount of dust. Working with explosive substances presupposes a complete knowledge of what an explosion is.

  

  For each type of dust, there is a so-called maximum permissible concentration, above which there is a danger of spontaneous explosion, and this amount of dust is measured in grams per cubic meter of air. The calculated concentration values ​​are not constant values ​​and should be corrected depending on humidity, temperature and other environmental conditions.

  The presence of methane is especially dangerous. In this case, there is an increased likelihood of detonation of dust mixtures. Already a five percent content of methane vapors in the air threatens to explode, due to which the dust cloud ignites and turbulence increases. Positive feedback is generated, resulting in a high energy explosion. Scientists are attracted by such reactions, the theory of the explosion is still haunted by many.

  Safe when working in confined spaces

  When working in confined spaces with a high dust content in the air, it is imperative to adhere to the following safety rules:

  Dust removal by ventilation;

  Fight against excessive dryness of the air;

  Dilution of the air mixture to reduce the concentration of explosives.

  Dust explosions are typical not only for mines, but also for buildings and granaries.

  Explosions of steam clouds

  They are reactions of a lightning-fast change of state, which generate the formation of a blast wave. Occur outdoors in a confined space due to ignition of a combustible vapor cloud. As a rule, this happens when a leak occurs.

  

  Refusal to work with flammable gas or steam;

  Refusal from sources of ignition that can cause a spark;

  Avoiding confined spaces.

  It is necessary to sensibly understand what an explosion is, what kind of danger it carries. Failure to comply with safety rules and illiterate use of some items leads to disaster.

  Gas explosions

  The most common gas explosion accidents occur as a result of improper handling of gas equipment. Timely elimination and characteristic identification are important. What does gas explosion mean? It occurs due to improper operation.

  

  In order to prevent such explosions, all gas equipment must undergo regular preventive technical inspection. All residents of private households, as well as apartment buildings, are recommended an annual VDGO maintenance.

  To reduce the consequences of an explosion, the structures of the premises in which the gas equipment is installed are made not capital, but, on the contrary, lightweight. In the event of an explosion, there is no major damage or debris. Now you can imagine what an explosion is.

  

  In order to make it easier to identify the leakage of domestic gas, an aromatic additive ethyl mercaptan is added to it, which causes a characteristic odor. If there is such a smell in the room, it is necessary to open the windows to provide fresh air. Then you should call the gas service. During this time, it is best not to use electrical switches that could spark. Smoking is strictly prohibited!

  A pyrotechnic explosion can also be a threat. The warehouse for such items must be equipped in accordance with the regulations. Poor quality products can harm the person who uses them. All this should be taken into account by all means.

  Physical explosion - caused by a change in the physical state of a substance. Chemical explosion- is caused by the rapid chemical transformation of substances, in which potential chemical energy is converted into thermal and kinetic energy of the expanding explosion products. Emergency, this is an explosion that occurred as a result of a violation of production technology, errors of service personnel, or mistakes made in the design.

  Explosive "medical environment" - represents the part of the room in which an explosive atmosphere can develop in low concentrations and only for a short time due to the use of medical gases, anesthetics, skin cleansers or disinfectants.

  The main damaging factors in an explosion are an air shock wave, fragmentation fields, propelling effects of surrounding objects, thermal factor (high temperature and flame), exposure to toxic products of explosion and combustion, psychogenic factor.

  Explosive trauma occurs when the destructive effect of an explosion on people in a confined space or in an open area, as a rule, characterized by open and closed wounds, trauma, contusion, hemorrhage, including into the internal organs of a person, ruptured eardrums, bone fractures, skin burns and respiratory tract, suffocation or poisoning, post-traumatic stress disorder.

  Explosions at industrial enterprises: deformation, destruction of technological equipment, power systems and transport lines, collapse of structures and fragments of premises, leakage of toxic compounds and poisonous substances. Explosive technological lines:

  Grain elevators: dust,

  Mills: flour,

  Chemical plants: hydrocarbons, oxidants. In addition to oxygen, oxidizing agents are oxygen-containing compounds (perchlorate, saltpeter, gunpowder, termite), individual chemical elements (phosphorus, bromine).

  Gas stations and refineries: vapors and aerosols of hydrocarbons.

  Distance of defeats on the example of an explosion of a tanker 5 t. Baiker U. 1995) I. Thermal injury from a fireball: - up to 45 m. Incompatible with life, - up to 95 m. - up to 145 m. Burns of the II degree. - up to 150 m. Burns of the 1st stage. - up to 240 m. Retinal burns. II. Mechanical damage by a shock wave: - up to 55 m. Not compatible with life, - up to 95 m. TBI, barotrauma of the lungs and gastrointestinal tract, - up to 140 m. Rupture of the tympanic membranes.

  The blast shock wave can cause great loss of life and destruction of structures. The size of the affected areas depends on the power of the explosion. The extent to which secondary measures are used depends on the likelihood of a hazardous explosive atmosphere occurring. Hazardous areas are divided into different zones according to the time and local conditions, the probability of the presence of a hazardous explosive atmosphere.

  Zone 0. An area containing a persistent, frequent or long-term hazardous explosive atmosphere and where a hazardous concentration of dust, aerosols or vapors may be generated. Such as mills, dryers, mixers, silos, production facilities using fuel, product pipelines, feed pipes, etc.

  Zone 1. An area where, due to the concentration of flammable vapors, aerosols, vortex, deposited dust, an accidental occurrence of a hazardous explosive atmosphere can be expected. Close proximity to loading hatches; at the sites of filling or unloading equipment; in areas with fragile equipment or lines made of glass, ceramics, etc .;

  Zone 2: An area in which a hazardous explosive environment can be expected, but very rarely and for a short time.

  Dust explosion risk assessment

  In the immediate vicinity of devices containing dust from which it can escape, settle and accumulate in hazardous concentrations (mills). In the case of an explosion of dust with a low concentration in the environment, the head compression wave of the explosion can cause a vortex motion of the deposited dust, which gives a high concentration of combustible material. The risk of explosion of a dust mixture is much less than gas, steam or fog. The zones of accidents with volumetric explosions can cover large areas. Gas pipeline accident in Bashkiria (June 1989) 2 q. km. Killed-871, wounded 339 people. The problem of saving people after an explosion and a fire was that almost all medical equipment for providing emergency aid burned out in the flames, and about improvised means in such cases, victims and rescuers have practically forgotten.

  The main criteria that determine the amount of sanitary losses: type of explosive device, explosion power, place of explosion and time of day. Depending on the number and localization, damage can be isolated, multiple and combined. According to the severity of injuries: light, moderate, severe and extremely severe. Table 4.1. shows the degree of damage to people depending on the magnitude of excess pressure.

  When in contact with an explosive device, an explosive destruction of the outer parts of the body or destruction (separation) of segments of the limbs occurs. In this case, the wound process has a number of features: - Acute massive blood loss and shock; - Bruises of the lungs and heart; - Traumatic endotoxicosis; - The combined nature of the impact of damaging factors.

  An explosion is a fast-moving process of physical and chemical transformations of substances, accompanied by the release of a significant amount of energy in a limited volume, as a result of which a shock wave is formed and spreads, which can lead and lead to a man-made emergency.

  Explosion characteristics:

  • * high rate of chemical transformation;
  • * a large number of gaseous products;
  • * strong sound effect (rumbling, loud sound, noise, strong clap);
  • * powerful crushing action.

  Explosions are classified according to the origin of the released energy into:

  • · Chemical.
  • Explosions of containers under pressure (gas cylinders, steam boilers):
  • · Explosion of expanding vapors of a boiling liquid (BLEVE).
  • · Explosions on release of pressure in superheated liquids.
  • · Explosions when mixing two liquids, the temperature of one of which is much higher than the boiling point of the other.
  • · Nuclear.
  • · Electrical (eg during a thunderstorm).
  • Supernova explosions

  Depending on the environment in which the explosions occur, they can be underground, ground, air, underwater and above water.

  The magnitude of the consequences of explosions depends on their power and the environment in which they occur. The radii of the affected areas during explosions can be up to several kilometers.

  There are three zones of explosion.

  Zone I - the zone of action of the detonation wave. It is characterized by an intense crushing action, as a result of which the structures are destroyed into separate fragments, scattering at high speeds from the center of the explosion.

  Zone II - zone of action of explosion products. It happens complete destruction buildings and structures under the influence of expanding explosion products. At the outer boundary of this zone, the resulting shock wave breaks away from the explosion products and moves independently from the explosion center. Having exhausted their energy, the explosion products, expanding to a density corresponding to atmospheric pressure, do not produce any more destructive action.

  Zone III - the zone of action of the air blast wave - includes three subzones: III a - severe destruction, III b - medium destruction, III c - weak destruction. At the outer boundary of zone III, the shock wave degenerates into a sound wave, which can still be heard at considerable distances.

  Explosion effect on buildings, structures, equipment.

  Buildings and structures of large sizes with light load-bearing structures, which significantly rise above the earth's surface, are subjected to the greatest destruction by explosion products and shock waves. Underground and buried structures with rigid structures have significant resistance to destruction.

  Destruction is divided into full, strong, medium and weak.

  Complete destruction. In buildings and structures, ceilings collapsed and all the main load-bearing structures were destroyed. Recovery is impossible. Equipment, means of mechanization and other machinery cannot be restored. In utility and energy networks, there are cable breaks, destruction of pipeline sections, supports of overhead power lines, etc.

  Strong destruction. In buildings and structures there are significant deformations of the supporting structures, most of the floors and walls have been destroyed. Restoration is possible, but impractical, as it practically boils down to new construction using some of the surviving structures. Equipment and mechanisms are mostly destroyed and deformed. In utility and energy networks, there are breaks and deformations in certain sections of underground networks, deformations of overhead power transmission and communication lines, ruptures of technological pipelines.

  Medium destruction. In buildings and structures, mainly secondary structures (light walls, partitions, roofs, windows, doors) were destroyed. Cracks in the outer walls and collapses in some places are possible. The ceilings and basements are not destroyed, some of the structures are serviceable. In utilities and energy networks, the destruction and deformation of elements is significant, which can be eliminated by overhaul.

  Weak destruction. In buildings and structures, part of the internal partitions was destroyed, door and window openings were filled. The equipment has significant deformations. There are minor destructions and breakdowns of structural elements in utility and energy networks.

  By the origin of the released energy.

  Chemical explosions.

  There is no consensus on which chemical processes should be considered an explosion. This is due to the fact that high-speed processes can proceed in the form of detonation or deflagration (combustion). Detonation differs from combustion in that chemical reactions and the process of energy release proceed with the formation of a shock wave in the reacting substance, and the involvement of new portions of explosive in a chemical reaction occurs at the front of the shock wave, and not through heat conduction and diffusion, as in combustion. Generally, the detonation rate is higher than the burning rate, but this is not an absolute rule. The difference in the mechanisms of energy and substance transfer affects the rate of the processes and the results of their action on the environment, however, in practice, a variety of combinations of these processes and transitions of detonation to combustion and vice versa are observed. In this regard, various fast processes are usually referred to chemical explosions without specifying their nature.

  There is a more rigid approach to defining a chemical explosion as exclusively detonation. From this condition, it necessarily follows that in a chemical explosion accompanied by a redox reaction (combustion), the combusting substance and the oxidant must be mixed, otherwise the reaction rate will be limited by the rate of the oxidant delivery process, and this process, as a rule, has a diffusional character. For example, natural gas burns slowly in home stove burners as oxygen slowly enters the combustion area by diffusion. However, if you mix gas with air, it will explode from a small spark - a volumetric explosion.

  Individual explosives, as a rule, contain oxygen in their own molecules, moreover, their molecules, in fact, are metastable formations. When such a molecule is given sufficient energy (activation energy), it spontaneously dissociates into constituent atoms, from which the explosion products are formed, with the release of energy exceeding the activation energy. Molecules of nitroglycerin, trinitrotoluene, etc. have similar properties. Cellulose nitrates (smokeless powder), black powder, which consists of a mechanical mixture of a combustible substance (charcoal) and an oxidizer (various nitrates), are not prone to detonation under normal conditions, but they are traditionally referred to as explosives.

  Explosions of containers under pressure

  Pressure vessels are hermetically sealed containers designed for conducting chemical and thermal processes, as well as for storing and transporting compressed, liquefied and dissolved gases and liquids under pressure. The main danger in the operation of such vessels is the possibility of their destruction in the event of a sudden adiabatic expansion of gases and vapors (i.e., a physical explosion). The reasons for the explosion of pressure vessels may be mistakes made in the design and manufacture of the vessel, defects in materials, loss of strength as a result of local overheating, impacts, excess of working pressure as a result of the absence or malfunction of instrumentation, absence or malfunction of safety valves, membranes, shut-off and shut-off valves. Explosions of vessels containing a flammable medium are especially dangerous. fragments of tanks, even of a large mass (up to several tons), fly up to a distance of several hundred meters and when falling on buildings, technological equipment, containers cause destruction, new hotbeds of fire, death of people.

  Nuclear explosion

  A nuclear explosion is an uncontrollable process of releasing a large amount of thermal and radiant energy as a result of a chain nuclear fission reaction or a thermonuclear fusion reaction in a very short period of time. By origin nuclear explosions are either a product of human activity on Earth and in near-earth space, or natural processes on some types of stars. Artificial nuclear explosions are powerful weapons designed to destroy large ground and protected underground military facilities, accumulations of enemy troops and equipment (mainly tactical nuclear weapons), as well as complete suppression and destruction of the opposing side: destruction of large and small settlements with civilians and strategic industries (Strategic nuclear weapons).

  Fission chain reaction

  Atomic nuclei of some isotopes chemical elements with a large atomic mass (for example, uranium or plutonium), when they are irradiated with neutrons of a certain energy, they lose their stability and decay with the release of energy into two smaller and approximately equal in mass fragments - the fission reaction of an atomic nucleus occurs. In this case, along with fragments with high kinetic energy, several more neutrons are released, which are capable of causing a similar process in neighboring atoms of the same kind. In turn, the neutrons formed during their fission can lead to the fission of new portions of atoms - the reaction becomes a chain reaction, acquires a cascade character. Depending on the external conditions, the amount and purity of the fissile material, its flow can occur in different ways. The emission of neutrons from the fission zone or their absorption without subsequent fission reduces the number of fissions in new stages of the chain reaction, which leads to its attenuation. At equal number of split nuclei in both stages, the chain reaction becomes self-sustaining, and if the number of split nuclei is exceeded in each subsequent stage, more and more atoms of the fissioning substance are involved in the reaction.

  Thermonuclear fusion

  Thermonuclear fusion reactions with the release of energy are possible only among elements with a low atomic mass, not exceeding approximately atomic mass gland. They are not of a chain nature and are possible only at high pressures and temperatures, when the kinetic energy of colliding atomic nuclei is sufficient to overcome the Coulomb repulsion barrier between them, or for an appreciable probability of their coalescence due to the tunneling effect quantum mechanics... For this process to be possible, it is necessary to perform work to accelerate the initial atomic nuclei to high speeds, but if they merge into a new nucleus, then the energy released during this process will be greater than the expended one. The appearance of a new nucleus as a result of thermonuclear fusion is usually accompanied by the formation of various kinds elementary particles and high energy quanta electromagnetic radiation.

  Nuclear explosion phenomena

  The phenomena accompanying a nuclear explosion vary from the location of its center. Below we consider the case of an atmospheric nuclear explosion in the surface layer, which was the most frequent before the ban on nuclear tests on the ground, under water, in the atmosphere and in space. After the initiation of a fission or fusion reaction, in a very short time of the order of fractions of a microsecond, in a limited volume, great amount radiant and thermal energy. The reaction usually ends after evaporation and expansion of the structure of the explosive device due to the tremendous temperature (up to 10 7 K) and pressure (up to 10 9 atm.) At the point of explosion. Visually, from a great distance, this phase is perceived as a very bright luminous point.

  During the reaction, light pressure from electromagnetic radiation heats up and displaces the surrounding air from the point of explosion - a fireball is formed and a pressure jump between the compressed radiation and unperturbed air begins to form, since the speed of movement of the heating front is initially many times greater than the speed of sound in the medium. After the damping of the nuclear reaction, the energy release stops and further expansion occurs due to the difference in temperatures and pressures in the area of ​​the fireball and the surrounding air.

  Nuclear reactions occurring in the charge serve as a source of various radiation: electromagnetic radiation in a wide spectrum from radio waves to high-energy gamma quanta, fast electrons, neutrons, and atomic nuclei. This radiation, called penetrating radiation, has a number of consequences characteristic only of a nuclear explosion. Neutrons and high-energy gamma-quanta, interacting with the atoms of the surrounding matter, transform their stable forms into unstable ones. radioactive isotopes with different paths and half-lives - they create the so-called induced radiation. Along with fragments of atomic nuclei of a fissile substance or products of thermonuclear fusion left over from an explosive device, the newly obtained radioactive substances rise high into the atmosphere and are able to disperse over a large area, forming a radioactive contamination of the area after a nuclear explosion. The spectrum of unstable isotopes formed during a nuclear explosion is such that radioactive contamination of the area can last for thousands of years, although the radiation intensity decreases with time.

  A ground nuclear explosion, unlike a conventional one, also has its own characteristics. In a chemical explosion, the temperature of the soil adjacent to the charge and involved in motion is relatively low. In a nuclear explosion, the temperature of the soil rises to tens of millions of degrees and most of the heating energy in the very first moments is emitted into the air and additionally goes into the formation of thermal radiation and a shock wave, which does not occur in a conventional explosion. Hence, there is a sharp difference in the impact on the surface and the soil mass: a ground explosion of a chemical explosive transfers up to half of its energy into the soil, and a nuclear explosion transfers only a few percent. Accordingly, the dimensions of the funnel and the energy of seismic vibrations from a nuclear explosion are several times less than those from an explosive explosion of the same power. However, when the charges are deepened, this ratio is smoothed out, since the energy of the superheated plasma is less released into the air and goes to work on the ground.

  Explodes within 0.0001 seconds, releasing 1.470 calories of heat and approx. 700 liters of gas. Cm. Explosives.

  The article reproduces the text from the Small Soviet Encyclopedia.

  Explosion, the process of releasing a large amount of energy in a limited amount in a short period of time. As a result of V., the substance filling the volume in which the energy is released is converted into a highly heated gas with very high pressure. This gas with great strength affects the environment by causing it to move. An explosion in a solid medium is accompanied by its destruction and crushing.

  The movement generated by the explosion, in which there is a sharp increase in pressure, density and temperature of the medium, is called blast wave... The front of the blast wave propagates through the medium at a high speed, as a result of which the area covered by the motion rapidly expands. The appearance of a blast wave is a characteristic consequence of V. in various environments. If the medium is absent, that is, an explosion occurs in a vacuum, the energy of V. is converted into kinetic energy of the products B. scattering in all directions at high speed. different distances from place B. As the distance from the explosion site increases, the mechanical effect of the blast wave weakens. The distances at which the blast waves create the same force of impact at different energies at V., increase in proportion to the cube root of the V.

  Various types of explosions differ in the physical nature of the energy source and the way it is released. Explosions of chemical explosives are typical examples of explosives. Explosives They are capable of rapid chemical decomposition, in which the energy of intermolecular bonds is released in the form of heat. Explosives are characterized by an increase in the rate of chemical decomposition with increasing temperature. At a relatively low temperature, chemical decomposition proceeds very slowly, so that the explosive may not undergo a noticeable change in its state for a long time. In this case, between the explosive and environment thermal equilibrium is established, in which continuously released small amounts of heat are removed outside the substance by means of thermal conduction. If conditions are created under which the released heat does not have time to be removed outside the explosive, then due to an increase in temperature, a self-accelerating process of chemical decomposition develops, which is called thermal V. Due to the fact that heat is removed through the outer surface of the explosive, and its release occurs during the entire volume of the substance, thermal equilibrium can also be violated with an increase in the total mass of the explosive. This circumstance is taken into account when storing explosives.

  Another process of the explosion is possible, in which the chemical transformation propagates through the explosive sequentially from layer to layer in the form of a wave. The leading front of such a wave moving at a high speed is shock wave- an abrupt (abrupt) transition of a substance from an initial state to a state with very high pressure and temperature. An explosive compressed by a shock wave is in a state in which chemical decomposition proceeds very rapidly. As a result, the region in which the energy is released turns out to be concentrated in a thin layer adjacent to the surface of the shock wave. The release of energy ensures that the high pressure in the shock wave is maintained at a constant level. The process of chemical transformation of an explosive, which is introduced by a shock wave and is accompanied by a rapid release of energy, is called detonation... Detonation waves propagate through the explosive at a very high speed, always exceeding the speed of sound in the starting material. For example, the velocities of detonation waves in solid explosives are several kilometers per second. A ton of solid explosive can be transformed in this way into a dense gas with a very high pressure in 10 -4 seconds. The pressure in the gases formed during this reaches several hundred thousand atmospheres. The effect of the explosion of a chemical explosive can be enhanced in a certain direction by using explosive charges of a special form (see. Cumulative effect).

  Explosions associated with more fundamental transformations of substances include nuclear explosions... In a nuclear explosion, the atomic nuclei of the initial substance are converted into the nuclei of other elements, which is accompanied by the release of the binding energy of elementary particles (protons and neutrons) that make up the atomic nucleus. Nuclear V. is based on the ability of certain isotopes of the heavy elements, uranium or plutonium, to fission, in which the nuclei of the starting material disintegrate to form nuclei of lighter elements. When all the nuclei contained in 50 g of uranium or plutonium are fissioned, the same amount of energy is released as in the detonation of 1000 tons of TNT. This comparison shows that nuclear transformation is capable of producing an explosion of enormous power. Fission of a uranium or plutonium atom nucleus can occur as a result of the capture of one neutron by the nucleus. It is essential that fission produces several new neutrons, each of which can cause fission of other nuclei. As a result, the number of divisions will grow very quickly (according to the law of geometric progression). If we assume that with each fission act the number of neutrons capable of causing the fission of other nuclei doubles, then in less than 90 fission events such a number of neutrons is formed, which is sufficient for the fission of nuclei contained in 100 kg of uranium or plutonium. The time required for the division of this amount of substance will be ~ 10 -6 sec. This self-accelerating process is called a chain reaction. Nuclear chain reactions). In reality, not all neutrons produced by fission cause the fission of other nuclei. If the total amount of fissile matter is small, then most of the neutrons will escape the matter without causing fission. There is always a small amount of free neutrons in fissile matter, however, a chain reaction develops only when the number of newly formed neutrons exceeds the number of neutrons that do not produce fission. Such conditions are created when the mass of the fissile substance exceeds the so-called critical mass. V. occurs when the individual parts of the fissile matter quickly combine (the mass of each part is less than the critical one) into one whole with a total mass exceeding the critical mass, or under strong compression, which reduces the surface area of ​​the substance and thereby reduces the number of neutrons escaping outside. To create such conditions, a chemical explosive is usually used.

  There is another type of nuclear reaction - the reaction of fusion of light nuclei, accompanied by the release of a large amount of energy. The repulsive forces of the electric charges of the same name (all nuclei have a positive electric charge) prevent the fusion reaction from proceeding, therefore, for effective nuclear transformation of this type, the nuclei must have high energy. Such conditions can be created by heating substances to a very high temperature. In this regard, the fusion process taking place at a high temperature is called a thermonuclear reaction. In the fusion of deuterium nuclei (isotope of hydrogen ²H), almost 3 times more energy is released than in the fission of the same mass of uranium. The temperature required for fusion is reached by a nuclear explosion of uranium or plutonium. Thus, if fissile matter and hydrogen isotopes are placed in one and the same device, then a fusion reaction can be carried out, the result of which will be V. of enormous strength. In addition to a powerful blast wave, a nuclear explosion is accompanied by intense emission of light and penetrating radiation (see. The damaging factors of a nuclear explosion).

  In the types of explosion described above, the liberated energy was initially contained in the form of molecular or nuclear bond energy in matter. There are V. in which the released energy is supplied from an external source. An example of such a V. can serve as a powerful electric discharge in any medium. Electrical energy in the discharge gap is released in the form of heat, converting the medium into an ionized gas with high pressure and temperature. A similar phenomenon occurs when a powerful electric current on a metal conductor, if the current strength is sufficient to quickly convert the metal conductor into steam. V.'s phenomenon also arises when a focused laser radiation(cm. Laser). One of the types of explosion can be considered the process of rapid release of energy, which occurs as a result of the sudden destruction of the shell holding the gas with high pressure (for example, the explosion of a cylinder with compressed gas). V. can occur in the collision of rigid bodies moving towards each other at high speed. On collision kinetic energy bodies transforms into heat as a result of the propagation of a powerful shock wave through the substance, which arises at the moment of collision. The speeds of the relative approach of solids, necessary for the substance to completely turn into vapor as a result of the collision, are measured in tens of km / sec, the pressures developing in this case are millions of atmospheres.

  Many different phenomena occur in nature, which are accompanied by V. Powerful electrical discharges in the atmosphere during a thunderstorm (lightning), sudden volcanic eruption, large meteorites are examples different types B. As a result of the fall Tunguska meteorite() there was V., equivalent in the amount of released energy V. ~ 10 7 tons of trinitrotoluene. Apparently, even more energy was released as a result of the explosion of the Krakatoa volcano ().

  Explosions of huge scale are chromospheric flares in the sun. The energy released during such flares reaches ~ 10 17 J (for comparison, we point out that at 10 6 tons of trinitrotoluene, an energy equal to 4.2 · 10 15 J would be released).

  The nature of giant explosions occurring in outer space are flares new stars... During flares, apparently within several hours, an energy of 10 38 -10 39 J is released. Such energy is emitted by the Sun for 10-100 thousand years. Finally, even more gigantic waves, which go far beyond the limits of human imagination, are flashes supernovae, at which the released energy reaches ~ 10 43 J, and V. in the nuclei of a number of galaxies, the energy estimate of which leads to ~ 10 50 J.

  Explosions of chemical explosives are used as one of the main means of destruction. Nuclear explosions have an enormous destructive power. Explosion of one nuclear bomb can be equivalent in energy to tens of millions of tons of chemical explosive.

  Explosions have found widespread peaceful use in scientific research and in industry. V. made it possible to achieve significant progress in the study of the properties of gases, liquids, and solids at high pressures and temperatures. High pressure). Explosion research plays important role in the development of the physics of nonequilibrium processes, which studies the phenomena of transfer of mass, momentum and energy in various media, mechanisms phase transitions substances, the kinetics of chemical reactions, etc. Under the influence of V., such states of substances can be achieved that are inaccessible with other methods of research. Powerful compression of the channel of an electric discharge by means of a chemical explosive makes it possible to obtain, within a short period of time, magnetic fields huge tension [up to 1.1 ha / m (up to 14 million oe), see. A magnetic field... Intense emission of light in the presence of a chemical explosive in a gas can be used to excite an optical quantum generator (laser). Explosive stamping, explosive welding and explosive hardening of metals are carried out under the influence of high pressure, which is created during the detonation of an explosive.

  Experimental study of V. consists in measuring the velocities of propagation of blast waves and the velocities of movement of matter, measuring rapidly changing pressure, distributions of density, intensity, and spectral composition of electromagnetic and other types of radiation emitted at V. These data make it possible to obtain information about the rate of occurrence of various processes. accompanying V., and determine the total amount of released energy. The pressure and density of the substance in the shock wave are related by certain ratios with the speed of the shock wave and the speed of movement of the substance. This circumstance makes it possible, for example, based on measurements of velocities, to calculate pressures and densities in those cases when their direct measurement turns out to be unavailable for some reason. To measure the main parameters characterizing the state and speed of movement of the medium, various sensors are used that convert a certain type of exposure into an electrical signal, which is recorded using oscilloscope or other recording device. Modern electronic equipment makes it possible to register phenomena occurring during time intervals of ~ 10 -11 sec. Measurements of the intensity and spectral composition of light radiation using special photocells and spectrographs serve as a source of information about the temperature of a substance. High-speed photography, which can be performed at a speed of up to 10 9 frames per second, is widely used for recording the phenomena accompanying V.

  In laboratory studies of shock waves in gases, a special device is often used - a shock tube (see. Aerodynamic tube). A shock wave in such a pipe is created as a result of the rapid destruction of the membrane separating gas with high and low pressure (such a process can be considered as the simplest type of V.). When studying waves in shock tubes, interferometers and penumbra optical devices are effectively used, the action of which is based on a change in the refractive index of a gas due to a change in its density.

  Explosive waves, propagating long distances from the place of their origin, serve as a source of information about the structure of the atmosphere and the inner layers of the Earth. Waves at very large distances from the place V. are recorded by highly sensitive equipment, which makes it possible to record pressure fluctuations in the air up to 10 -6 atmospheres (0.1 n / m²) or soil displacement ~ 10 -9 m.

  Literature:

  • Sadovskiy MA, Mechanical action of air shock waves of explosion according to experimental research data, in collection: Fizika explosion, No. 1, M., 1952;
  • Baum F.A., Stanyukovich K.P. and Shekhter B.I., Explosion Physics, M., 1959;
  • Andreev K.K. and Belyaev A.F., Theory of explosives, M., 1960:
  • Pokrovsky G.I., Explosion, M., 1964;
  • Lyakhov GM, Fundamentals of explosion dynamics in soils and liquid media, M., 1964;
  • Dokuchaev M.M., Rodionov V.N., Romashov A.N., Explosion for release, M., 1963:
  • R. Cole, Underwater Explosions, trans. from English, M., 1950;
  • Underground nuclear explosions, trans. from English, M., 1962;
  • Action nuclear weapons, per. from English., M., 1960;
  • Gorbatsky V.G., Space explosions, M., 1967;
  • Dubovik A.S., Photographic registration of fast processes, M., 1964.

  K. E. Gubkin.

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