A History of Research and a Review of Recent Developments

The decay of instantaneous overpressure in free air 21
compare p 0 and R, that led to Eq. (1.9), she also measured positive phase
durations, and from these results proposed the relationship
(1.24)
where z=R/W 1/3 in ft/lb 1/3 , t 0 is measured in milliseconds, and typical values of
c 1, and d 1, are:
4000 lb bomb, high capacity, c1=8.1, d1=4.8 1000 lb bomb, medium capacity, c1=6.9, d1=4.2 1000 lb bomb, general purpose, c1=6.2, d1=3.8 As Figure 1.9 shows, the scatter is small. Similar curves to Figure 1.9, but for
nuclear explosions were given in many publications in the 1950s.
A knowledge of the instantaneous pressure and the duration of the positive
phase allows us to calculate the blast impulse of an explosion. This is usually
expressed per unit of projected area, and in imperial units is lb sec/in 2 or lb
msec/in 2 . For the three bombs analysed by Philip, she found that a simple
relationship between impulse (I), charge weight and radius took the form
I=K 1 W 2/3 /R,
(1.25)
Figure 1.9 Relationship between scaled duration and scaled range (from Philip, ref.
1.15).