A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
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Above-ground explosions 33<br />
Figure 2.8 Variation <strong>of</strong> p r /p 0 with angle <strong>of</strong> incidence (from Glasstone <strong>and</strong> Dolan,<br />
ref. 2.9).<br />
The properties <strong>of</strong> obliquely reflecting shock waves have been a subject <strong>of</strong><br />
much theoretical <strong>and</strong> experimental research over the years. Theories due to<br />
von Neumann [2.7] <strong>and</strong> more recently to Dewey <strong>and</strong> McMillin [2.8] have<br />
used different approaches (pseudo-stationary <strong>and</strong> non-stationary) to predict<br />
more accurately the point at which transition to Mach reflection occurs. It is<br />
near this transition that the total pressure exceeds the normal reflection pressure.<br />
The theoretical results have been used to predict the peak hydrostatic<br />
overpressure at ground level from an air burst explosion, <strong>and</strong> are <strong>of</strong>ten expressed<br />
as isobars <strong>of</strong> overpressure plotted on the axes <strong>of</strong> height <strong>of</strong> burst <strong>and</strong> ground<br />
radius. Curves <strong>of</strong> this type were presented by Glasstone <strong>and</strong> Dolan [2.9], <strong>and</strong><br />
an adaptation <strong>of</strong> their results by Satori [2.10].<br />
In a paper in 1985 by Dewey, Heilig <strong>and</strong> Reichenbach [2.11] on oblique<br />
reflections, experiments performed at the Ernst Mach Institut in Freiburg,<br />
Germany were reported for the first time. Small spherical charges <strong>of</strong> hexogen<br />
(0.016 to 1.024 kg) were detonated at heights ranging from 0.15 to 6.5 m<br />
over flat concrete reflecting surfaces. Pressure gauges were flush mounted in<br />
the surface between 0 <strong>and</strong> 8 m radius from a point immediately below the<br />
charge. The test results were compared with experiments at the Defence<br />
<strong>Research</strong> Establishment, Suffield, where 500 kg charges <strong>of</strong> TNT <strong>and</strong> 100 <strong>and</strong><br />
500 kg charges <strong>of</strong> pentolite were detonated at heights ranging between 1.2<br />
<strong>and</strong> 44 m. The results were also compared with experiments at Suffield with<br />
450 000 kg <strong>of</strong> TNT at a height <strong>of</strong> 4 m. By applying the scaling laws to the<br />
hexogen <strong>and</strong> pentolite explosions it was possible to compare the relation<br />
between p 0/p a <strong>and</strong> the primary shock front radius in metres, on a basis <strong>of</strong> a 1<br />
kg charge mass <strong>of</strong> TNT. This comparison is shown in Figure 2.9, where a