Game Development Reference
In-Depth Information
The efficiency factor accounts for the fact that for many explosives only some fraction of
the total specific combustion energy is converted into explosive energy.
Once the equivalent TNT mass for the given explosive is computed, the scaled distance
and overpressure for the explosion can be determined from Equations (13.1) and (13.2) just as
was done when TNT was the explosive. Sometimes the specific combustion energies and effi-
ciency factor are combined into a single TNT equivalence factor,
h
equiv
.
Δ
=
Δ
H
H
η
η
ex
(13.6)
equiv
TNT
Using Equation (13.6), the equivalent TNT mass for a given explosive can be written in
terms of the mass of the explosive and its TNT equivalence factor.
m
=
m
η
(13.7)
equiv TNT
,
ex
equiv
Table 13-3 shows the equivalence factors for a number of different explosives.
2, 4, 5
TNT is
the standard, of course, so its TNT equivalence factor is 1. C4 is 18% more powerful than TNT.
Ammonium nitrate in its pure form is a fairly weak explosive. When combined with fuel oil,
however, it gains an explosive power nearly equal to TNT.
Table 13-3.
Explosive-Specific Combustion Energies and Equivalence Factors
Explosive
TNT Equivalence factor
TNT
1.0
C4
1.18
Ammonium nitrate
0.1-0.2
Ammonium nitrate with fuel oil
0.8
Natural gas
0.16
Other Explosion Models
As you might guess, the TNT equivalency model is not the only one available to model the effects
of explosions. Other explosion models include the TNO, Multi-Energy, and Baker-Strehlow
models. Details of these alternative explosion models won't be discussed in this chapter, but
more details about these models can be found in the document “A Comparison of Vapor Cloud
Explosion Models” (see the “References” section at the end of this chapter for details). The
alternative models are available to use as options if the TNT equivalency model doesn't work
for your particular game application.
TNT Equivalence of Bombs
It was mentioned before that TNT is used as a standard explosive against which other explosives
are compared. The damage caused by a explosion can be enhanced if the explosive material is
encased in another object. Terrorists frequently use car, briefcase, or pipe bombs to devastating
effects. Typical TNT equivalence values in
kg
for various types of bombs
1
are shown in Table 13-4.