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SENSITIVITY TESTS
5.3 Large-Scale Drop Test or Spigot Test. This test, developed by LASL, is used
to help assess the safety of large explosive charges subjected to combined
mechanical impact and shearing and, possibly, adiabatic heating. A 6-in.-diam, 4-
in.-high right circular cylinder of high explosive weighing 7-9 lb, and usually at its
working density, is glued into the counterbore of an inert ‘plastic-bonded material
that has about the same shock impedance characteristics. The inert material is an
8-3/4-in.-high truncated cone with diameters of 12-3/4 in. at the top and 8-314 in. at
the bottom. A l/2-in.-thick Micarta plate is glued to its top surface to hold a wire
sling that is used to raise the assembly. A l/2-in.-thick steel plate glued to the bot-
tom surface has a 3/4-in.-diam hole in its center and a 1-3/16-in.-diam, l/4-in.-deep
counterbore cut from the surface facing the HE. A steel pin with a 1-l/8-in.-diam,
l/4-in.-thick head and a 1-l/4-in.-long, 3/4-in.-diam shaft is placed through this
hole so that its shaft protrudes from the bottom of the HE. As assembled, the head
of the steel pin is separated from the bottom surface of the explosive by a 0.35 to
0.50-mm gap and the shaft extends 25 mm beyond the bottom surface of the steel
plate.
A test normally consists of 20 drops performed by following the up-and-down
technique. The results are reported in terms of the drop height that produces events
in half of the trials and of the magnitude of the event.
458
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INERT
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8 an.
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DROP VEHICLE
TARGET
Fig. 5.02. Drop test assembly.
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