Game Development Reference
In-Depth Information
1.
Compute the scaled distance based on the distance from the target to the point of
explosion and the amount of TNT that is exploding using Equation (13.1).
2.
Use the scaled distance value to calculate the overpressure for the shock wave from
Equation (13.2).
3.
Use the computed overpressure value to estimate the damage inflicted on the structure
or person from the information in Tables 13-1 and 13-2.
Example: Computing the Blast Damage for a Soldier Standing
by a Window
Let's go through the process of a TNT blast damage calculation. A 5
kg
charge of TNT is deto-
nated 8
m
from a soldier who is standing next to a wood-framed building with glass windows.
What will happen to the soldier and building when the TNT explodes? The first step in the
process is to determine the scaled distance for the explosion based on Equation (13.1)
8
Z
==
4.68
(13.3)
3
5
Using the scaled distance value in Equation (13.3), the overpressure experienced by the
soldier and building can be determined from Equation (13.2).
⎛
⎞
2
⎛
⎞
⎟
4.68
⎜
⎜
⎟ ⎟
808 1
⎜ +
⎟
⎟
⎜
⎜
⎜
⎟
⎟
⎝
4.5
⎠ ⎟
⎝
⎠
N/m
2
p
=
101325
=
33046
(13.4)
0
2
2
2
⎛
⎞
⎛
⎞
⎛
⎞
4.68
4.68
4.68
⎟
⎟
⎟
⎜
⎜
⎜
1
+
1
+
1
+
⎟
⎟
⎟
⎜
⎜
⎜
⎜
⎟
⎜
⎟
⎜
⎟
⎝
⎠
⎝
⎠
⎝
⎠
0.048
0.32
1.35
Based on Tables 13-1 and 13-2, the soldier will be knocked down and his eardrums will be
close to rupturing. The windows of the building will shatter and the building will suffer signifi-
cant structural damage but probably won't collapse entirely.
Blast Damage from Other Types of Explosives
The TNT explosion model, as the name would suggest, is designed to compute the overpressures
due to a TNT explosion. But how would one compute the overpressure from other types of
explosives? As you might guess, many different models have been developed over the years to
compute overpressure for other types of explosives. One of the simplest and most widely used
models, and the one we will discuss in this chapter, is called the
TNT equivalence model
.
The TNT equivalence model is based on converting the explosive being considered to an
equivalent mass of TNT by equating the energy released by the two explosives. The
equivalent
mass
of a given explosive,
m
equiv,TNT
, is equal to the mass of the explosive,
m
ex
, multiplied by
its specific combustion energy,
Δ
H
ex
, and an efficiency factor,
h
, and divided by the specific
combustion energy of TNT,
Δ
H
TNT
.
mH
Δ
η
ex
ex
m
=
(13.5)
equiv TNT
,
Δ
H
TNT
