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Anexplosive booster is a sensitiveexplosive charge that acts as a bridge between a (relatively weak) conventionaldetonator and a low-sensitivity (but typically high-energy) explosive such asTNT.[1] By itself, the initiating detonator would not deliver sufficient energy to set off the low-sensitivity charge. However, it detonates the primary charge (the booster), which then delivers an explosiveshockwave that is sufficient to detonate the secondary, main, high-energy charge.
UnlikeC4plastic explosive, not all explosives can be detonated simply by inserting a detonator and firing it.
An initiator such as ashock tube, cannonfuse, or even a conventionaldetonator does not deliver sufficient shock todetonate charges comprisingTNT,Composition B,ANFO and many otherhigh explosives. Therefore, some form of "booster" is required to amplify the energy released by the detonator so that the main charge will detonate.
At first,picric acid was used as a booster to detonate TNT, though it was superseded due to the inherent danger ofpicrate formation.Tetryl replaced picric acid because it is more stable, and was once a very popular chemical for booster charges, particularly duringWorld War II. However, since then, tetryl has largely been replaced by other compositions, e.g. a small cylinder or pellet ofphlegmatizedRDX (e.g. CH-6 or Composition A-5) orPETN (slightly larger than the actualdetonator) into which the detonator itself is inserted.
Note:booby traps andimprovised explosive devices frequently useplastic explosive as the booster charge, for example, someC4 orSemtex stuffed into the emptyfuze pocket of a 120mmmortar shell. This is because any standard detonator will initiate plastic explosive as is.
When encountered in connection with artillery shells or air dropped bombs, a booster charge is sometimes referred to as the "gaine", fromFrench:gaine-relais. Seedetonators.
At a purely technical level, a sufficiently large detonator would initiate high explosives without the need for a booster charge. However, there are very good reasons why this method is never used. Firstly, there is a major safety issue, i.e. detonators are (like allprimary explosives) much more sensitive to shock, heat, and friction than an explosive booster. Therefore, minimising the amount of primary explosive that users must store or carry greatly reduces the likelihood of serious accidents. An additional economic reason for using explosive booster charges is that chemical compounds used in detonators (e.g.lead styphnate) are comparatively expensive to produce and encapsulate when compared to the manufacturing costs of explosive boosters.
A common form for boosters is to cast the explosive material into a cylindrical shell made of cardboard or plastic; these are accordingly known ascast boosters.
