Game Development Reference
In-Depth Information
Certain explosives such as C4 and TNT are stable enough that they need a detonator in
order to explode. A detonator is a smaller explosive charge that is used to initiate the explosion
of a larger explosive. Typical detonator explosive materials include mercury fulminate and
diazodinitrophenol, also known as DDNP. The detonator charge is typically set off either elec-
trically, where the detonator is attached to wires that are connected to a battery, or electronically.
Blast Damage
An explosion is a rapid release of energy. The energy of the explosion can be converted to light,
heat, sound, and a blast wave . A blast wave is a region of highly compressed air or other gas
that travels radially outwards from the point of explosion. The blast wave moves very quickly—
well over 1000 km / hr . Behind the shock wave is a region of low pressure. Air rushes into this
low-pressure region, causing a wind effect. The wind caused by an explosion can actually
change direction. Initially the wind will be in the direction of the advancing shock wave. As the
shock wave progresses, the wind can reverse direction depending on the relative pressures in
front of and behind the shock.
The high pressures that exist in the blast wave are the primary cause of damage to buildings
and other structures from an explosion. When a strong blast wave hits a building, the windows
and possibly the exterior walls may be pushed inwards and break. Once the shock wave enters
the interior of the building, it will press both upwards on the ceiling and possibly also down-
wards on the floors. The floors themselves may collapse because they have a large surface area
for the pressure to act upon and are generally not designed to withstand the forces exerted by
the blast wave. When modeling the effects that explosions have upon buildings, you should
keep in mind this sequence of events.
The damage done to a structure is a function of the overpressure that exists in the shock
wave. If you recall from Chapter 3, the force exerted on an object due to a pressure is equal to
the pressure multiplied by the area on which the pressure acts. Table 13-1 shows the magni-
tude of overpressures, in N / m 2 , that are typically required to cause certain types of structural
damage. 1, 2 Keep in mind when looking at Table 13-1 that atmospheric pressure at sea level is
101,325 N / m 2 .
Table 13-1. Building and Structural Damage Levels Due to Blast Wave Overpressures
Overpressure ( N / m 2 )
Damage Type
1000-1500
Window breakage
4000-5000
Minor structural damage to homes
10,000
Serious structural damage to homes
40,000
Collapse of wood-framed building
70,000
Probable destruction of all buildings
Any people inside a building subjected to a blast wave will suffer injuries in proportion to
the damage done to the building. Shattered windows can cause lacerations to people behind them.
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