Game Development Reference
In-Depth Information
As an example, let's use Equation (13.8) to compute the initial velocity of the fragments
from an M-61 hand grenade. The M-61 uses 0.185
kg
of an explosive material known as Comp-B for
its explosive charge. Comp-B has a heat of explosion of 4.04
e
+ 6
J
/
kg
. The mass of the metal
casing is 0.210
kg
. Using the spherical constant shown in Table 13-5, the initial velocity of the
fragments is as follows:
2
m
s
0.185 / 0.21
2
v
=
2 * 4.04
e
+
6
=
4.656
e
+
6
(13.9)
(
)
2
1
+
0.6 0.185 / 0.21
2158
m
v
=
----
(13.10)
Once the initial velocity of the fragments is known, they can be treated like any other
projectile. The forces of aerodynamic drag and gravity will slow down the fragments and cause
them to eventually hit the ground. If a fragment hits an object, the penetration through the
object can be modeled according to the relations that were discussed in Chapter 12.
To determine whether a fragment hits a target, several assumptions can be made. The
blast wave can be assumed to be spherical. The distribution of fragments can be assumed to be
spherical as well. The surface area of a sphere is proportional to the square of the sphere radius.
2
(13.11)
Ar
=
π
If the fragments are evenly distributed around the sphere, the number of fragments per
unit area,
n
, is equal to the total number of fragments,
N
, divided by the surface area of the sphere.
N
n
=
(13.12)
2
4
π
r
Equation (13.12) can be used to determine the number of fragments that will strike a given
target. Once the distance from the target to the point of explosion is determined, the number
of fragments per unit area can be determined from Equation (13.12). Multiplying this value by
the frontal area of the target gives the number of fragments that strike the target. This approach
works best if the target is relatively close to the fragmentation device. Gravity will pull the fragments
towards the earth, and this effect will become more pronounced the longer the fragments have
been flying.
Nuclear Explosions
Unlike chemical explosions that are caused by chemical reactions and the sudden release of
chemical energy, a nuclear explosion is caused by the splitting or forced combination of atoms.
Nuclear explosions can be extremely powerful. The blast wave can damage structures and
people miles away from the point of explosion. The winds following the blast wave can have
speeds of several hundred
km
/
hr
. It is the combination of the blast wave and the wind effects
that cause most of the damage from a nuclear explosion. Nuclear explosions also generate size-
able amounts of harmful radiation.
Nuclear weapons, or nukes, can be designed to explode in the atmosphere, on the ground,
under the ground, or underwater. A nuke that is exploded on the ground or underwater throws
a lot of dirt, water, and other debris into the air into a mushroom-shaped cloud. A typical
mushroom cloud is shown in Figure 13-3.
