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SENSITIVITY TESTS
5.2 Skid Test. The skid test used at LASL is a modification of one designed by the
Atomic Weapons Research Establishment in cooperation with the Explosives
Research and Development Establishment, both of the United Kingdom. The in-
tent of this test, sometimes called the oblique impact test, is to simulate a bare ex-
plosive charge accidentally hitting a rigid surface at an oblique angle during han-
dling. In these circumstances, combined impact, friction, and shearing forces
generate thermal energy.
In the most common version of this test, an uncased hemispherical charge, 254
mm in diameter, is dropped vertically in free fall onto a rigid target inclined at a 45”
angle. In a second version, the hemispherical charge swings down in a harness on the
end of a cable and strikes a rigid horizontal target at a predetermined angle.
In either version, the variables are the drop height, the angle of impact between
target and explosive, and the target surface.
Two target surfaces have been used. The first is a thin (lo-gauge) steel pad
painted with epoxy resin sprinkled with sea sand. After curing, this surface resem-
bles coarse sandpaper. Closekote, 80D-grit garnet paper bonded with epoxy resin to
the surface of a 6.3-mm-thick Dural plate has also been used. The steel or
aluminum target is placed on a rigid steel pad, 114.3 mm thick.
A standard test consists of 10 to 15 drops performed by following the up and down
techniques normally used in sensitivity testing. The overpressure at a distance of 10
ft is measured with an Atlantic Research Model LC-13 pressure gauge. Results
reported are the drop height that produces events in 50% of the trials and the
average overpressure. This test measures each of initiation (drop height) and ease of
detonation growth (overpressure).
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