Primary explosives explosive trains

An explosive device is initiated or detonated by an explosive train — an arrangement of explosive components by which the initial force from the primary explosive is transmitted and intensified until it reaches and sets off the main explosive composition. Most explosive trains contain a primary explosive as the first component. The second component in the train will depend on the type of initiation process required for the main explosive composition. If the main explosive composition is to be detonated, the second component of the train will burn to detonation so that it imparts a shockwave to the main composition. This type of explosive train is known as a detonator. Detonators can be initiated by electrical means, friction, flash, or percussion. 

Explosives are classed as primary or secondary. Typically, a small quantity of a primary explosive would be used in a detonator (known colloquially as a cap ), whereas larger quantities of secondary explosives are used in the booster and the main charge of a device. This collection of explosives is known as an explosive train in which a signal (mechanical, thermal, or electrical) from the control system is converted first into a small explosive shock from the detonator, which in turn initiates a more powerful explosion in the booster, which amplifies the shock into the main charge. 

The requirement for an explosive train, that is, a primary explosive to initiate the secondary explosive, is a safety feature. In the past, people wishing to illegally use explosives usually had to steal the detonators (e.g., Timothy McVey). Consequently, the effective control of access to detonators has been widely regarded as a key pubhc safety measure by many governments and law enforcement agencies. However, recently, triacetone triperoxide (TATP) has been used as the primary explosive (e.g., Richard Reid s shoe bomb) and TATP is readily, although hazardously, synthesized from acetone, hydrogen peroxide, and acid. 

The unusual danger to pubHc safety in the case of peroxide explosives is not their explosive performance but their ease of initiation and the ease with which terrorists have acquired and used the materials for their synthesis, although synthesis is actually quite hazardous. Both TATP and HMTD are classed as primary explosives. For example, Richard Reid, the would-be shoe bomber, used TATP as part of his firing train in the attempted bombing of a US airfiner in December 2001, or the use of HMTD in the London bombings of 7 July 2005. HMTD was also one of the materials prepared and carried over the US/Canadian border in December 1999 by Ahmed Ressam as the ingredient for the initiators of his devices. 

In early days Alfred Nobel already replaced mercury fulminate (MF, see above), which he had introduced into blasting caps, with the safer to handle primary explosives lead azide (LA) and lead styphnate (LS) (Fig. 1.17). However, the long-term use of LA and LS has caused considerable lead contamination in military training grounds which has stimulated world-wide activities in the search for replacements that are heavy-metal free. In 2006 Huynh und Hiskey published a paper proposing iron and copper complexes of the type [cat]2[Mn(NT)4(H20)2] ([cat]+ = NH4, Na+ M = Fe, Cu NT = 5-nitrotetrazolate) as environmentally friendly, green primary explosives (Fig. 1.17) [3]. 

Primary explosives are substances which show a very rapid transition from deflagration to detonation and generate a shock-wave which makes transfer of the detonation to a (less sensitive) secondary explosive possible. Lead azide and lead styphnate are the most commonly used primary explosives today. However, the long-term use of these compounds (which contain the toxic heavy metal lead) has caused considerable lead contamination in military training grounds. Costly clean-up... 

Uses In the explosive train of H. E. shell between the primary explosive and the main bursting charge to insure complete detonation of the bursting charge and to permit the use of a smaller amount of the dangerous primary explosive. 

Part of an explosive train which initiates the - detonation of high explosives, especially of insensitive ones. It may itself be triggert by a seperate -> primer of primary explosives or an integrated primer. Detonators are classified by the method of initiation percussion, stab, electrical impulse, or flash. Laser initiation is also used. Depending on the application detornators can include a delay mechanism. Explosive charge placed in certain equipment and set to destroy the equipment under certain conditions (- Initiator). 

The sequence of functions incorporated in such a series, as primary explosive, booster, secondary (or "main charge") explosive, is called an explosive train. The elements or components of such a train may themselves also consist internally of a sequence of explosives, the selection of a component depending on the nature of the stimulus applied, whether from a preceding element or from a source external to the train. 

Other investigators [135-140] have studied the initiation of secondary explosives by laser radiation. With direct initiation of secondary explosives, for example, by incorporating a fiber optic cable interfacing the main charge, primary explosives become unnecessary, thus providing increased safety and reliability in explosive trains. 

The primary safety considerations in the formulation, manufacture, and use of explosives are that they must never explode prematurely but always explode when desired. Often this balance is achieved with an insensitive main charge being initiated by the least amount of a more sensitive explosive. This concept is expanded to that of an explosive train in which a series of decreas-ingly sensitive explosives is ultimately sufficient to initiate an insensitive main charge. The sensitivity of explosives to initiation provides a common means of classification ... 

In a general approach we explain why one should start with the generation of structural models (RD, HDD, IBD, PD) and afterwards generate the behavioural models (UCD, AD, SMD, SD). The generation process is illustrated using the interrupted fiize train architecmre that is used if primary explosives are present in the fiize train in military fuzing systems. 

Primary eKplosivee are energetic materials that are sensitive to initiation by heat, sp2urk, impact, or friction. Their primary application is as the first element in an explosive train, which is a. sequence of explosive materials varying in sensitivity. The first element, called the primer, is the most sensitive and is used U> initiate the second element, often called the booster. The booster adds energy to the detonation wave generated by t he primer and is used to initiate the main chargo of the... 

The determination of the initiating strength or priming ability of primary explosives is very important for the correct solution of tasks related to the service application of the primary explosives in initial devices, explosive trains, etc. 

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