A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
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The development <strong>of</strong> low <strong>and</strong> high explosives 5<br />
lower <strong>and</strong> the duration <strong>of</strong> the impulse much greater. Detonation, as opposed to<br />
deflagration, is obtained by the use <strong>of</strong> a burster charge containing a mass <strong>of</strong><br />
conventional high explosive about one-hundredth <strong>of</strong> the FAE mass. The control<br />
<strong>of</strong> FAE weapons was thought to be uneven, <strong>and</strong> research in the USA was reduced<br />
in the 1970s, but more recently the Soviet air force used weapons <strong>of</strong> this type in<br />
Afghanistan, <strong>and</strong> there are reports in the technical military press <strong>of</strong> the very<br />
successful use <strong>of</strong> FAE bombs by the US forces in the Gulf War.<br />
Let us now turn to the detonation process, which has been considerably<br />
developed during the past century. There are now many methods for the safe<br />
detonation <strong>of</strong> high explosives, <strong>and</strong> nearly all consist <strong>of</strong> the initiation <strong>of</strong> a<br />
shock wave into a base charge which then detonates the main explosive charge.<br />
Most recruits to the armed services in the first half <strong>of</strong> this century will have<br />
h<strong>and</strong>led the small aluminium tubes containing a priming charge <strong>of</strong> mercury<br />
fulminate (HgC 2N 2O 2), or lead azide (PbN 6) <strong>and</strong> a secondary charge <strong>of</strong> PETN.<br />
The primary charge could be set <strong>of</strong>f by impact, as in the spring released system<br />
<strong>of</strong> a h<strong>and</strong> grenade, or via a length <strong>of</strong> safety fuse capable <strong>of</strong> initiation by a<br />
safety match.<br />
The priming charge can also be ignited by electrical means, <strong>and</strong> electrical<br />
shotfiring is now widely used. When an electrical charge is connected to the<br />
detonator it heats up a fine wire which then ignites a flashing compound. This<br />
‘fusehead’ fires the primer <strong>and</strong> base charges. Delaying elements can be<br />
introduced between the fusehead <strong>and</strong> the primary charge, or the fusehead can<br />
be set to explode so quickly that the entry <strong>of</strong> the firing current <strong>and</strong> the detonation<br />
<strong>of</strong> the base charge is virtually instantaneous. The use <strong>of</strong> electrical detonation<br />
must be carefully controlled in very sensitive environments where there is a<br />
risk <strong>of</strong> premature firing by static electricity, or where there are dangerous<br />
methane or dust clouds. Special detonators have been developed to overcome<br />
these problems <strong>and</strong> to avoid accidental pre-detonation. These are described<br />
in h<strong>and</strong>books <strong>and</strong> in the marketing literature <strong>of</strong> manufacturers such as ICI<br />
Nobel <strong>and</strong> Dupont.<br />
The other main detonating medium is the ‘detonating cord’ <strong>and</strong> ‘Cordtex’<br />
is a universally used version in blasting <strong>and</strong> quarrying operations, explosive<br />
cutting, <strong>and</strong> underwater operations. A core <strong>of</strong> PETN is surrounded by tape<br />
<strong>and</strong> wrapped with textile or synthetic yarn, <strong>and</strong> this cord is completely enclosed<br />
by a white plastic tube. It has a high velocity <strong>of</strong> detonation which means that<br />
it will initiate most commercial explosives, <strong>and</strong> it can be initiated itself by<br />
most <strong>of</strong> the st<strong>and</strong>ard detonators. There is plenty <strong>of</strong> information on methods<br />
<strong>of</strong> using Cordtex for various blasting operations, involving detonating relays,<br />
jointing <strong>and</strong> branching methods, <strong>and</strong> initiating systems.<br />
A major area <strong>of</strong> development has been the artillery fuse. These were originally<br />
the powder train fuses, or rather inaccurate mechanical devices, but more<br />
recently the need for high firing rates has led to the evolution <strong>of</strong> the electronic<br />
time fuse <strong>and</strong> to the electronic fuse with a high-explosive boosting charge.<br />
The fuse is the shaped end <strong>of</strong> a mortar or artillery projectile <strong>and</strong> consists <strong>of</strong> an