A History of Research and a Review of Recent Developments

148
Penetration and fragmentation
The penetration length, L, which is the total length of the J-path, not the
final vertical depth, p, was found from the tests to be linked to striking velocity
through the parameter , where W p is the total projectile weight, not
the weight of the explosive charge (W). The curves shown in Figure 7.2 are
taken from ref. [7.13], and refer to four types of soil and projectiles having an
‘average’ nose shape. Detailed information on other nose shapes are given in
the reference.
The vertical penetration of a range of general purpose bombs, with total
weights in the range 100 to 2000 lb, in three different soils, is given in Figures
7.3, 7.4 and 7.5. The curves were said by Stipe to agree with the scatter of
available data to within ±20%, and a rough interpolation between curves
could be made for other soil types. Because the tests were mainly carried out
with free-dropped aerial bombs, the striking velocity has been replaced by the
altitude from which the bombs were dropped in level flight. In each experiment,
delay fusing prevented explosion until full penetration had been achieved,
and the results confirm the earlier statement that penetration into clay is about
Figure 7.2 Length of the J-shaped penetration path (from Stipe, ref. 7.11; US Army
TM5–855–1, 1965 and 1986).