Detonation is a process of supersonic combustion that involves a shock wave and a reaction zone behind it. The shock compresses the material thus increasing the temperature to the point of ignition. The ignited material burns behind the shock and releases energy that supports the shock propagation. This self-sustained detonation wave is different from a deflagration that propagates with a subsonic speed and without a shock. Detonations generate high pressures and are usually much more destructive than deflagrations.
Detonations can be produced by high explosives, reactive gaseous mixtures, certain dusts and aerosols. Thermonuclear detonations are believed to be involved in Type Ia supernova explosions.
Detonations are hard to control and are used primarily for demolition and in warfare. A great deal of research is conducted on achieving or preventing detonation in various materials to improve the performance of explosives and engines. An experimental form of jet propulsion, the pulse detonation engine, uses detonation to generate thrust.
Detonation in otto-cycle engines is caused usually by heat (or by pressure) resulting in a premature ignition (preignition, knocking). This force is extremely destructive to engines, and often results in holes blown through the top of pistons or engine blocks. This is different from diesel engines, which use detonation as their primary method of extracting energy from diesel.
In internal-combustion engines, detonation is sometimes called 'knock' and can harm or destroy an engine in less than a second.
Detonator is designed to be fired with a Capacitor Discharge Unit (CDU) fireset with a capacitor in the range of 0.05 to 0.3 µF. The CDU supplies a rapidly rising current pulse on the order of several thousand amps to the detonator to cause it to function.
The detonators were also subjected to a constant current at 45% of the MNDC level established for the detonators (2 Amps) for three minutes.
The specified detonators were subjected to thermal shock between temperatures of -46° C and +71° C. The detonators were subjected to a total of 35 cycles, beginning with the cold temperature.
The exploding-bridgewire detonator (EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnston for the Fat Man-type bombs of the Manhattan Project, during their work in Los Alamos National Laboratory.
The implosion had to be very symmetric or the plutonium would simply squirt out at the low-pressure points.
The EBW and the slapper detonator are the safest known types of detonators, as only very high-current fast-rise pulse can successfully trigger them.
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