Initiation by shock

In a few instances there was evidence of a deflagration, but no detonations were observed Initiation by Shock is undoubtedly the most quantitatively reproducible of all the modes of... 

Related to both DDT and initiation by shock is the initiation of solid expls by gas detonations. Weiss et al (Ref 61) found that PETN at 0.7g/cc could be initiated by a gas detonation of 21 atm initial pressure, which produced an initial (presumably in the PETN) pressure of 2kbar. Under these conditions initiation delay in the PETN was less than one microsecond... 

Detonation in SP is initiated by shock or by DDT (deflagration to detonation transition). Let us first examine shock initiation, ie, initiation by in-contact or close-by detonation of HE... 

An explosive oxidant, readily initiated by shock or phase changes during condensation or evaporation, especially around -160°C. Handle only small quantities at moderately low temperatures. 

Explosive, initiated by shock, friction, pressure or temperatures over 30°C [1], It may also detonate spontaneously at ambient temperature [2],... 

Sodium reacts immediately and incandescently with iodine heptafluoride [5], Mixtures of solid sodium and iodine explode lightly when initiated by shock [6],... 

Mixtures of sodium with silver iodate or sodium iodate explode when initiated by shock. 

Initiation by shock can be instantaneous, or practically so, if the shock is strong enough. In secondary explosives the essential factor appears to be a pressure increase, specifically a pressure "jump of 25-50 atm1 ... 

M.A. Cook etal, TrFaradSoc 56, 1028-38(1960 Promotion of shock initiation of detonation by metallic surfaces) 36a) Andreev Belyaev (i960), 265-68 (Starting impulse and mechanism of initiation) 268-70 (Initiation by heat) 270-73 (Initiation by flame) 273-86 (Initiation by shock or friction) 287-89 (Initiation of expln in projectiles on hitting a target) 36b) J. Favier C. Fauquignon, MP 42, 65-81(1960) (Initiation of expls. and transmission of detonation) 37) D.B. Moore J.C. Rice, Detonation of Secondary Explosives by Lead Azide , SRI (Stanford Research Institute), Poulter Laboratories, Technical Report 004-60(1960) 37a) S.J. Jacobs, AmRocket-... 

Initiation by shock or impact is discussed under "Detonation (and Explosion), Initiation in Explosive Substances ... 

Detonation, Shock Sensitivity in. Sensitivity to shock of explosives, which might also be called "detonability by shock , has been recently measured, mostly by gap tests, using instead of air some plastic materials (such as Lucite) or cardboard for the gap. Some of these tests are described under "DETONATION (AND EXPLOSION), EXPERIMENTAL PROCEDURES IN and also under "DETONATION (AND EXPLOSION), INITIATION BY SHOCK ... 

Initiation by Influence usually called Sympathetic Initiation, is the initiation of an explosive charge by the detonation of a nearby charge separated from the first charge by an inert medium see Detonation by Influence in Vol 4, pp 395-398 and also Initiation by Hot Fragments Initiation by Shock... 

Initiation by Shock will be described in detail under Shock Sensitivity. Some of the tests for determining the shock sensitivity of explosives have already been given under Detonation (and Explosion) Experimental Procedures in Vol 4, pp D318-321, pp D322-331 D344. Some preliminary discussion of shock initiation is also given in Vol 4, pp D520-522... 

This value for the thickness of the hot layer is in agreement with the size of hot spot necessary for initiation by shock. 

They are sensitive to initiation by shock and, when detonated by a blasting cap, explode with tremendous brisance ... 

This compd is a weak expl, extremely insensitive to initiation by shock. It cannot be exploded in the liq state by a No 8 cap when in a Trauzl block but if mixed with kieselguhr (10/3 by wt) it can be exploded by a No 8 cap giving a net expansion of 45 cc in Pb block test... 

A.N. Afanasenkov, Ibid, 1970(68/25), 93—100 CA 73, 89720n(1970) [Detonation props of industrial expls, which included pressure of deton, critical pressure of initiation by shock waves and transmission distance of initiation of detonation (gap) were detd]... 

Recent developments of novel explosive materials have concentrated on reducing the sensitivity of the explosive materials to accidental initiation by shock, impact and thermal effects. The explosive materials, which have this reduced sensitivity, are call Insensitive Munitions, (IM). Although these explosive materials are insensitive to accidental initiation they still perform very well when suitably initiated. Examples of some explosive molecules under development are presented in Table 1.5. A summary of the significant discoveries in the history of explosives throughout the world is presented in Table 1.6. 

TATB is an explosive which is resistant to high temperatures, and therefore used in high-temperature environments or where safety from accidental fires is important. TATB is extremely insensitive to initiation by shock and requires a large amount of booster to initiate it. TATB is therefore regarded as an insensitive explosive and will most likely replace HMX and RDX in future explosive compositions. However, the cost of TATB is five to ten times greater than the cost of HMX. 

It is initiated by shock as readily as nitroglycerine a two kilogram weight dropped from a height of 4 cm causes a sample to explode. In direct contact with flame it melts and bums in the open air with difficulty. It bums evenly only after it has been wanned up. Andreyev [21] has reported that nitromannitol bums with appreciably more difficulty than nitroglycerine. In order to cause it to bum in a glass tube it was necessary to heat it to 95°C and to reduce the pressure to 85 mm Hg. 

His results are presented in the form of output energy (dent in witness plate) vs input shock (exit pressures in the barrier) curves. His curve for RDX, Fig 4, agrees with the writer s observation that coarse RDX is easier to initiate by shock than fine RDX... 

Diminished sensitivity has also been noted with decreasing temp over the range —100 to +22° (Ref 109), and at -196° (Ref 142). Increase of pressure over the range 50 to 200Kbar results in a greatly increased temp for initiation by shock of molten TNT (Ref 106). Cast TNT is less sensitive than the pressed material, as shown by the Gap Test (Vol 4, D321), and by projectile... 

Sodium ignites in fluorine gas but is inert in the liquefied gas [1]. Cold sodium ignites in moist chlorine [2] but may be distilled unchanged in the dry gas [1], Sodium and liquid bromine appear to be unreactive on prolonged contact [3], but mixtures may be detonated violently by mechanical shock [4]. Finely divided sodium luminesces in bromine vapour [1]. Iodine bromide or iodine chloride react slowly with sodium, but mixtures will explode under a hammer-blow [1]. Interaction of iodine pentafluoride with solid sodium is initially vigorous, but soon slows with film-formation, while that with molten sodium is explosively violent [2]. Sodium reacts immediately and incandescently with iodine heptafluoride [5]. Mixtures of solid sodium and iodine explode lightly when initiated by shock [6]. 

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