An explosion is the physical, exponentially coupled process of releasing large amounts of energy , generally in the form of temperature, pressure and kinetic energy .
The cause of the highly concentrated high amount of energy can be a chemical reaction (e.g. due to explosives , explosive atmosphere ), which leads to a sharp rise in temperature and pressure in a very short time . In chemical explosions, a very rapid reaction ( exothermic reactions such as combustion ) of an explosive mixture or a decomposition reaction takes place, in which large amounts of gas and heat are released and a strong pressure wave (air blast) due to the sudden expansion of the gas (or liquid in the Water shock from underwater explosions). The sudden expansion in volume causes a shock wave , which can be described by the model of the detonation wave in the case of an ideal explosion (starting from a point source) . An explosion is accompanied by a bright flash of light and a loud bang.
Other causes can also produce highly compressed gas bubbles, for example gases built up in volcanoes .
In general, a process is referred to as an explosion when a very large amount of energy is released in a very short time in the form of a strong increase in temperature and pressure, which leads to a strong increase in volume, i.e. accelerates matter. In contrast to this, there are also processes which, although they release large amounts of energy in a short time, are not referred to as explosions; for example because they have no direct effect on matter (examples: lightning in a thunderstorm, laser flash , gamma-ray flash ), or the release does not proceed quickly enough (example: rocket launch ).
There are two types of chemical explosions:
- Explosions heat (thermal explosions) are formed when the reaction heat of a chemical reaction is not dissipated fast enough and thus the temperature of the system increases. The rise in temperature leads to a higher reaction rate and thus to an even faster release of heat, which can ultimately lead to an explosion (theories of Semenov, Frank-Kamenitzkii and Thomas). An example of a thermal explosion is the chlorine detonating gas reaction .
- Chain branching explosions occur in radical reactions in which more chain branches than chain termination reactions (through recombination of radicals ) take place, so that the number of radicals and thus the reaction speed increases like an avalanche and leads to an explosion. Such chain branches occur in the oxyhydrogen reaction .
These types differ in the type of chemical reaction. In both cases, however, the thermodynamic process is the same: The released energy leads to a rapid increase in temperature and pressure and thus to a powerful volume expansion that splits the surrounding material apart. Many mixtures of substances can explode in both ways, depending on pressure, temperature and composition. The speed with which the reaction proceeds independently depends on the concentration ratio of the substances (e.g. gases and aerosols). There is a lower and an upper limit, also known as the explosion limit or ignition limit. Beyond these limits, independent explosion propagation in the mixture is no longer possible. The limits are not only dependent on concentrations, but also on environmental conditions such as temperature, pressure or humidity. Within these limits, for example, a mixture of air under atmospheric conditions can react with combustible substances in the form of dust, fibers or lint in a dust explosion .
Another distinction is made macroscopically :
- Deflagration , rapid combustion at the explosion limit with a low flame speed (<1 m / s) and pressure (<1 bar) and usually a thud.
- Deflagration , in which the speed of propagation of the flame or reaction front is slower than the speed of sound of the respective medium (the explosive ) and the plumes of exhaust gas move against the direction of propagation. In air, deflagration occurs at flame speeds below 330 m / s and pressure effects below 14 bar.
- Detonation thatpropagates in the medium at supersonic speed and in which the exhaust plumes move in the direction of propagation (flame speed over 330 m / s and pressure effect from 10 bar to 1000 bar). It is the fiercest reaction; it occurs mainly with explosives.
As far as atomic decay processes of very heavy chemical elements , namely uranium or plutonium , are triggered by a chain reaction by forces in atomic nuclei , a nuclear weapon explosion can occur. An explosion can also be achieved by fusing very light nuclei in so-called hydrogen bombs . In both nuclear fission and nuclear fusion , there is a loss of mass , the matter is converted into energy ( radiation and thermal energy ). This is where the greatest amounts of energy are released from all human-made explosions.
Finally, there are explosions in which no chemical or nuclear reaction takes place, but only an increasing pressure in a solid shell (e.g. gas-rich magma in a volcano or steam in a boiler ) causes it to burst. Sudden, very strong heating of liquids, which then change into a gaseous state with a large increase in volume, can lead to a physical explosion . For example, if a container (glass bottle, pressure cooker, boiler) filled with liquid or, in particular, gas under excess pressure bursts suddenly.
The counterpart to the explosion is the implosion , in which the reactive medium does not expand but contracts. Since the mechanical work leading to the implosion is done via the pressure of the surrounding atmosphere and is not released by an explosive device, the amount of energy, in contrast to that of an explosion, is limited by the imploding volume and the ambient conditions.
Cathode ray tubes on televisions or other display devices, light bulbs - both made of glass - can implode if damaged because they were evacuated during manufacture . Broken glass flying off can injure people nearby.
Explosions in nature
In nature, explosions mostly occur in connection with volcanism . This includes explosive volcanic eruptions (e.g. Krakatau 1883) or steam explosions . Water vapor explosions , a case of physical explosion , occur when water comes into contact with magma .
Impacts from meteorites can also lead to explosions if they hit the ground or water at sufficient speed or if they are slowed down very strongly as a result of air resistance in the atmosphere. In both cases the kinetic energy converted into heat in a very short time, which leads to explosive evaporation of meteorites and possibly the Auftreffmediums (soil water). In this way, impact craters are formed when land falls .
In astronomy, the end of the life cycle of massive stars is referred to by the term supernova . These represent the largest known form of an explosion (in relation to the energy released).
A few living things can cause / use explosions, such as the bombardier beetle .
Some ripe fruits, spore or seed carriers of plants can burst vigorously by themselves or through injury in order to distribute the contents spatially, e.g. B. the potato bovist .
Explosions as wanted or unwanted human work
Technically, two “types” of explosions can be distinguished, intentional and unintentional explosions. Deliberate explosions are usually described with the term detonation; they serve various technical ( quarries , mines , fireworks , tunnel construction , explosion engines ) or military purposes. The largest wanted explosion so far was that of the Tsar bomb , the largest hydrogen bomb ever detonated , which was detonated by the Soviet Union in 1961 and had an explosive force of 50 to 60 megatons of TNT .
Unwanted explosions practically always occur as a result of disturbed technical processes. This can be the incorrect operation of a gas connection in residential buildings or the unintentional release of gases with subsequent ignition in chemical plants, for example. Explosions of this type are divided into gas explosions or dust explosions according to the type of fuel . Chained explosions such as the so-called BLEVE are often possible. First a flammable liquid physically explodes and then a gas explosion follows. Therefore, when dealing with such processes and substances, comprehensive explosion protection must take place.
Examples of explosion accidents are the explosion at the Oppau nitrogen works , Piper Alpha or the explosion in Toulouse . The largest unintentional explosion to date is likely to be the Halifax explosion , an explosion caused by a fire on the ammunition freighter Mont Blanc , which had an explosive force of about three kilotons. This corresponds to about 23% of the explosive power of the Hiroshima bomb Little Boy . Around two thousand people were killed in the explosion.
Depending on the type, severity and distance of the explosion and other circumstances, typical damage to health occurs, such as tears in the lungs , ARDS , pop trauma , burns , severe injuries and states of shock . A distinction is made between primary (directly due to the explosion reaction), secondary (due to thrown fragments) and tertiary injuries (e.g. due to a fall or debris).
In Germany, causing an explosive explosion is a publicly dangerous offense according to § 308 StGB ( crime in the case of intent, offense in the case of negligence).
- ↑ a b c d e Henry Portz: Fire and Explosion Protection from A to Z - Explanation of terms and fire protection characteristics . Springer-Verlag, 2015, ISBN 978-3-322-80197-5 , pp. 1 ( limited preview in Google Book search).
- ^ H. Schubothe: Internal diseases caused by physical environmental factors. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition ibid. 1961, pp. 1161–1194, here: pp. 1191–1193 ( damage and illnesses caused by blasts of air ).
- ↑ Peter OK Krehl: History of Shock Waves, Explosions and Impact A Chronological and Biographical Reference . Springer Science & Business Media, 2008, ISBN 978-3-540-30421-0 , pp. 1272 ( limited preview in Google Book search).
- ↑ Gabriele Cruciani: Short textbook physical chemistry , Verlag John Wiley & Sons, 2006, ISBN 978-3-527-31807-0 , p. 512 
- ↑ W. Bartknecht: Explosions - Process and protective measures . Springer-Verlag, 2013, ISBN 978-3-662-07157-1 , pp. 1 ( limited preview in Google Book search).
- ↑ Kai-Uwe Schmitt, Peter F. Niederer, Duane S. Cronin, Markus H. Muser, Felix Walz: Trauma-Biomechanik: Introduction to the biomechanics of injuries , Verlag Springer-Verlag, 2014, ISBN 978-3-642-54281 -7 , p. 242 
- ↑ Walter J. Moore: Fundamentals of physical chemistry . Walter de Gruyter, 1990, ISBN 978-3-11-009941-6 , p. 343 ( limited preview in Google Book search).
- ↑ Ammann: Reinforced concrete and prestressed concrete structures under shock loads . Springer-Verlag, 2013, ISBN 978-3-0348-5365-1 , p. 24 ( limited preview in Google Book search).
- ↑ a b Karsten Schwanke, Nadja Podbregar, Dieter Lohmann: Natural disasters, cyclones, quakes, volcanic eruptions - unleashed violence and their consequences . Springer Science & Business Media, 2009, ISBN 978-3-540-88684-6 , pp. 35 ( limited preview in Google Book search).
- ^ John S. Lewis: Physics and Chemistry of the Solar System . Academic Press, 2004, ISBN 978-0-08-047012-2 , pp. 360 ( limited preview in Google Book Search).
- ↑ Benjamin Bahr, Jörg Resag, Kristin Riebe: Fascinating Physics An illustrated foray from the universe to the world of elementary particles . Springer-Verlag, 2014, ISBN 978-3-662-45348-3 , pp. 32 ( limited preview in Google Book search).
- ↑ Constanze Eisenbart: The Singular Weapon What remains of the atomic age? Springer-Verlag, 2012, ISBN 978-3-531-18730-3 , pp. 93 ( limited preview in Google Book search).
- ↑ Ulrich Hauptmanns: Process and plant safety . Springer-Verlag, 2013, ISBN 978-3-642-37253-7 ( limited preview in the Google book search).
- ↑ Nelles Verlag GmbH, Eva Ambros, Eleanor Morris, Mary Kelly, Valentin P. Nadezhnikov, Carla Straessle-Compton, Jonathan D. Siskin, J.-Martina Schneider, David Ravvin, Deborah Williams: Nelles Guide Canada - Eastern Ontario, Québec, Atlantic Provinces . Nelles Verlag, 2015, ISBN 978-3-86574-715-0 , pp. 188 ( limited preview in Google Book search).
- ↑ Jens Scholz, Bernd W. Böttiger, Volker Dörges, Volker Wenzel, Peter Sefrin: Emergency Medicine . Georg Thieme Verlag, 2012, ISBN 978-3-13-158983-5 , p. 453 ( limited preview in Google Book search).
- ^ Christian Neitzel, Karsten Ladehof: Tactical medicine, emergency medicine and emergency medicine . Springer-Verlag, 2015, ISBN 978-3-642-39689-2 , pp. 272 ( limited preview in Google Book search).
- Slow motion recordings of underwater explosions (Youtube, English)