EXPLOSION IN TURRET TWO
Investigation Continued

      they alone cannot assure against all forms of documented sealing defects.  Further, provision of ready-to-use ammunition to the fleet should by no means depend upon inspection by fleet users, whose experience and competence in such matters may be uncertain, and who must often replenish ammunition at sea in darkness and under adverse conditions.

b.   Gaps in the explosive filler:  Principal present suspect is a gap between the filler and either the projectile base or the tip of the BDF.  Paragraph 10 summarizes the basic problem, reference (j) shows the situation being found in current 8” HC, and paragraph 16 notes the extent of departures from the prescribed standard which are being identified.  Here again, the defects are attributable only to manufacturing and inspection deficiencies in our own Navy facilities.  Until some safe gap size for Explosive D is established (which would require extended testing, since negative information is all the results from each non-premature shot), the standards for Composition A-3 should be enforced for Explosive D as well, as is currently being done by reference (i).

40.           Two more possible sources of a projectile premature have been suggested.  These are noted as follows for the record, but no information yet available to us appears to justify their being regarded as significant to this casualty:

a.      Copper azide problem:  Reference (o) summarizes this situation.  Briefly, copper azide is extremely sensitive to shock, and can be formed internally in any fuze containing lead azide (as does the ADF Mk 55) which also includes exposed copper or copper-alloy elements (which we understand the ADF Mk 55 is not supposed to do).  Although the unsatisfactory production/inspection situation uncovered by reference (i) makes almost any defect believable, we judge that copper azide could not form in the Mk 55 in sufficient quantity in the necessary location to initiate the booster of the ADF Mk 55 prematurely, unless the fuze rotor were prearmed.  In the latter case the presence of copper azide could become one more of the possible causes of firing a pre-armed rotor, with a resulting projectile premature.

b.   Iron picrate problem:  There has been some concern that contact within the projectile cavity between Explosive D (ammonium picrate) and unprotected steel could result in the formation of iron picrates in a form highly sensitive to shock, and in quantity sufficient to initiate projectile detonation.  The possibility is intended to be protected against by specified cavity coatings.  At the direction of COMNAVORDSYSCOM ex-NEWPORT NEWS 8” projectiles are being subjected to breakdown and inspection, including chemical analysis of explosives.  We understand no abnormalities have been discovered thus far.  We can make no further assessment.

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