Electrical Initiation

With zero circuit resistance all except lead styphnate and lead dinitrores-orcinate are more sensitive to contact than to gaseous discharge. 

Lead styphnate is exceptionally sensitive to gaseous, and lead azide to contact, discharge. 

Material Contact sparks (500 pF) Gaseous sparks (100 pF) Minimum energy Minimum capacity (pF) 

Bowden and McLaren [94] used single crystals of silver azide whose dimensions were 1.0X0.5X0.5 mm and electrical resistance lO ohms. They made three different types of experiment. In the first they applied 45 V (d.c.) across a crystal and measured the current at different times. They found it increased with time, and when the current was 150 /xA, explosion took place for small fields the crystal was an ohmic conductor. In the second series of experiments they determined the breakdown voltage of a crystal at temperatures in the range 173-324°K. The field was applied for only a few seconds, and it was possible to remove the field before explosion occurred. They found that the breakdown of the resistance was not permanent. Table VI shows the breakdown voltages of a single crystal of AgNa at different temperatures. 

Finally, in the third series of experiments they applied an a.c. field of 9 X 10 V/m at various frequencies across the crystal and measured the time to explosion Table VII gives the results. 

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It is becoming increasingly clear that the preponderant amt of modern ordnance requiring the initiation of HE charges utilize electric initiation. However, there still remains a continued requirement for the use of percussion initiation. The use and description of sensitive artillery primers, eg, M29A1, etc, to accomplish this has previously been discussed... 

Whereas currently most studies deal with azides, a similar effort devoted to other metal salts such as nitrates and chlorates would be an important step toward understanding electrical initiation of pyrotechnics, and conversely to making possible safe, non-expl igniters. For instance, a study by Maycock (Ref 4) shows that those azides, perchlorates, and nitrates in which the solid state shows absorption on the long wavelength side of the anionic excitation band in soln, are the most unstable members of the respective series. Consequently, there is a direct relationship between the absorption spectra of pyrotechnic oxidizers and their respective sensitivities... 

A small sample of crystalline material on a sintered glass funnel detonated with extreme violence when touched with a metal spatula [1]. Static electrical initiation may have been involved [2],... 

Warm potassium reacts explosively with lead dioxide, and sodium probably behaves similarly [1], Magnesium reacts violently [2], and powdered aluminium probably does also, as it reacts violently with the monoxide [3], Mixtures of powdered molybdenum or tungsten with the dioxide incandesce on heating [4], The combination with zirconium is rated highest on a scale for sensitivity to deflagration, friction, ignition and static electrical initiation [5],... 

Squib. 1) (General). Any of various small size pyrotechnic or explosive devices 2) (Specific). A small explosive device similar in appearance to a detonator, but loaded with low explosive, so that its output is primarily heat (flash). Usually electrically initiated, and provided to initiate action of burning type munitions, pyrotechnic devices and rocket propellants. An electrical squib consists essentially of a tube containing a flammable material, and a small charge of powder compressed around a fine resistance wire connected to electrical leads or terminals (Ref 40a, p 135)... 

Electric Primer MK34 Mod O is similar in construction to MK15 primer, except that it is designed for electrical initiation only and cannot be activated by percussion (Ref 52, p 2-129)... 

Zn 83 Si 9.6 parts loaded in a fuze train 0.054 inches long gave a mean delay time of 0.023 sec, while 2) KMnC>4 100, Zn 111 70/30-Tl/Ni alloy 11 parts gave a mean time of 0.062 sec] Ad 112a) R.M. Hillyer R.H.F. Stresau EBW (Exploding Bridge Wire) Initiation of RDX with Fifty Milli-joules , Paper No 5, Electric Initiator Sum-posium, Franklin Institute, Philadelphia,... 

PATR 2110 B.A. Rausch, Application of an Improved Igniter Composition in Electric Initiating Devices (Jan 1955)... 

Military Standard. "Basic Evaluation Test for Use in Development of Electrically Initiated Explosive Components for Use... 

Hangfire Primers. A hangfire in small arms ammunition (initiated by a blow from a firing pin) can be defined as that condition which exists when initiation of the usual chain of events following the release of the trigger in a loaded weapon, occurs at a rate slower than normal the definition of hangfire for electrically initiated ammo is similar... 

ELECTRIC INITIATORS, EXPLOSIVE DEVICES, ASSEMBLIES, SUBSYSTEMS,... 

It should be stressed that all previously descrihed items may be mechanically or electrically initiated to explode when the envelopes or packages are opened, resulting, in death or injury to personnel. Should envelopes or packages resembling above descriptions be encountered, avoid handling the items insofar as possible, evacuate personnel from... 

There are also electric initiating devices, known as "bridgeless type electric cap . 

Flash F use. A small explosive device similar in appearance to a detonator, but loaded with LE (low explosive), so that its output is primarily heat (flash). Usually electrically initiated, and employed to initiate action of pyrotechnic devices and rocket propellants. 

The gun could lie on the ground, without any carriage, on blocks sloped at a 45°angle. The fin-stabilized arrow proj was inserted in the barrel and the base proplnt chge electrically initiated. As the proj passed the separate Y-pieces, addnl proplnt chges in... 

Pyrocartridges (also known as electrical initiators) are used to initiate the explosive train for specific applications in rockets and missiles. The pyrocartridges contain broadly the following ingredients or explosives. 

Electrically Initiated Explosive Devices, Bridgewire Welding for. See Hugh.H. Snider et al, NOLTR 65-37 (26 Feh 1965), Naval Ordnance Laboratory... 

Electric Initiators, Activated, can be divided in 5 main classes basedon the type of transducer used for conversion of the electrical stimulus (a) resistive bridgewire, exemplified by electric blasting caps, squibs,... 

Refs 1) R.I. Gray, "Hazards to Electrically Initiated Explosives in Weapon Systems , Ministry of Supply Rept DGGW 58/6(1958)... 

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