Initiation by impact

The studies of Bobolev et al (Ref 70) on the transition from burning to detonation have already been described in Section VIII under Initiation by Impact Friction... 

II is via penetration of hot combustion products into the existing pores of the expl. Propagation in Region III is via convective flow between the charge surface and its confinement. This regime is claimed to be affected by confinement expansion (due to pressure), and by fragmentation of the peripheral portions of the expl column. The phenomena in Regions IV and V have already been described in Section VIII under Initiation by Impact Friction... 

RDX may be used alone in pressed charges, although for this purpose tetryl is a more general choice. For shell and bomb fillings it is too sensitive alone to initiation by impact and friction and is either desensitised with wax, or else used like PETN in admixture with TNT. RDX may also be compounded with mineral jelly and similar materials to give a useful plastic explosive. 

The monomeric azide and several precursors are explosives of moderate to considerable sensitivity to initiation by impact, shock, friction or heat. 

The azide is very explosive, even when moist. Loosening the solid from filter paper caused frictional initiation. Explosion initiated by impact is very violent, and spontaneous explosion has also been recorded [1], It is also an exceptionally powerful initiator [2]. Detonation of the azide when dry has been confirmed [3], Good crystals are considerably more sensitive to shock, friction and electric discharge than is powder [4],... 

Lead azide (PbN6) is a colorless to white crystalline explosive. It is widely used in detonators because of its high capacity for initiating secondary explosives to detonation. However, since lead azide is not particularly susceptible to initiation by impact, it is not used alone in initiator components. It is used in combination with lead styphnate and aluminum for military detonators, and is used often in a mixture with tetrazene. It is compatible with most explosives and priming mixture ingredients. Contact with copper must be avoided because it leads to formation of extremely sensitive copper azide. 

Lerom, M. W. et al., J. Chem. Eng. Data, 1974, 19, 389-392 Several difluoroaminopolynitro derivatives of stilbene, biphenyl, terphenyl and their precursors are explosives, sensitive to initiation by impact, shock, friction or rapid heating. 

Several fluorodinitro compounds of methane (1,1,1-) and ethane (1,2,2-) are described as explosive, sensitive to initiation by impact, shock, friction or other means [1]. Procedures for safe handling of fluorine and explosive fluoronitro compounds are detailed [2],... 

Birth (Initiation) and Growth of Explosion in Solid and Liquid Explosives Initiated by Impact, Friction, etc. See Vol 2, p B127-L and under Detonation (and Explosion), Initiation (Birth), Growth, Spread and Propagation in Explosive Substances... 

M. Sultanoff, PrRoySoc 246A, 274-81 (1958) (Sympathetic deton and initiation by impact) 21) Dunkle s Syllabus (1957-1958), p 152 (Some work conducted at BRL on sympathetic deton is briefly discussed)... 

M. Sultanoff, "Sympathetic Detonation and Initiation by Impact , PrRoySoc 246A,... 

J- Wenograd, "A Photographic Study of Explosion Initiated by Impact , pp 10-23 in the 3rdONRSympDeton (I960)... 

Fuze, Spitback or Fuze, Flashback. A fuze located in the forward part of a shaped charge munition. When initiated by impact it produces a detonation which is directed toward the element located in the base of munition and this, in turn, detonates the main explosive charge. The combination of point impact fuze and base element is referred to as point initiating base detonating" (PIBD) fuzing system... 

A necessary but not sufficient condition for initiation by impact is that impact pressure (stress) be sufficiently high so that the melting point of the explosive is raised above some critical temperature, TCr- For T>Tcr the explosive, in the hot spot, will decompose adiabati-cally in times of the order 10/usec, which has been observed experimentally. The relation between Tcr the critical stress is then expressed... 

Initiation by Impact is described in detail in this Vol under Impact. Tests in which initiation may occur as a result of dropping an explosive device are described under Drop Tests in Vol 5, pp D1549-1554... 

Gases Liberated from Explosions Initiated by Impoct. It has been known for a long rime that in a true deton of HE, the major products are C02, CO, HaO, N and H, while in thermal decomposition of expls, more complicated mixtures of NOa, NO, NgO, C02, CO, H2, aldehydes etc, result. As it is of interest to know what kind of products are obtained when an expl is initiated by impact, Robertson and Yoffe (Ref 8) tested NG,... 

RDX is a white, crystalline solid with a melting temperature of 204 °C. It attained military importance during World War II since it is more chemically and thermally stable than PETN and has a lower sensitiveness. Pure RDX is very sensitive to initiation by impact and friction and... 

The above data show that FGAN is not abnormally sensitive to initiation by impact, friction or heat, but the molten FGAN is much more sensitive than the cryst material. However, a 52-lb wt allowed to fall 10 ft on a mixt of molten FGAN and-bagging paper confined in a steel tube caused no expln. The impact on,and immersion in similar mixes of burning wood or charcoal also failed to cause deton of FGAN, The probability of expln by impact on molten FGAN appears to be unlikely... 

Due to their extreme sensitivity only a few azides are suitable for use in the expl industry (Ref 3). The prepn and props of most known azides are described in the general Refs 2,4,5,6,8,9,10,11,12,14,15,17,18,19 25 27 their structure and stability (Refs 13, 14a,25 26) their sensitivity to initiation by impact and heat (Refs 7,8,20 21) their thermochemisty (Refs 23 24) the theory of decompn (Refs 16 16a) Raman spectra (Ref 18a)jand their analytical determn (Ref 22) are described in the references indicated... 

Detonation Rate, 1500 m/sec (unconfined and initiated by hot wire), 1700 m/sec (unconfined and initiated by impact with grit particle), and... 

Birth (initiation) and growth of expln in solid and liquid expls initiated by impact, friction, etc 2B127... 

---