Game Development Reference
In-Depth Information
The power density,
I
, is typically expressed in units of
W
/
cm
2
and is equal to the power of
the laser beam,
P
, in
W
divided by the area of the beam,
A
, that strikes the target. The absorbed
energy can be expressed in terms of the beam power and area.
Pt
E
=
α
(14.5)
A
The energy absorbed by the target in Equations (14.4) and (14.5) is really the energy absorbed
per unit area and typically has units of
J
/
cm
2
. The use of
cm
rather than
m
in these expressions
is a standard convention. In looking at Equation (14.5), you might wonder, since there is a time
factor in the equation, whether any laser could meet the required energy density if it was focused
on the target for a long enough time. The problem with this line of thinking is that the energy
applied to the target by the laser will dissipate fairly quickly. It will radiate back into the air, be
conducted throughout the target material, or be removed by convection. In order to melt through
a material, the energy from the laser must be absorbed in a short enough period of time to
overwhelm the dissipative mechanisms. So a 1
MW
laser applied for 0.1 seconds is not the
same as a 1
W
laser applied for 100,000 seconds.
There are a lot of ways that a military laser can damage a target, and you can have some
“fun” when modeling the effects. A laser beam could melt through a fuel tank, causing it to
explode. It could similarly cause bombs or other munitions stored on board a tank, airplane, or
helicopter to explode. The beam could blind the pilot of an aircraft or disable the plane's elec-
tronic systems, causing the aircraft to careen off into a hillside. A laser could conceivably cause
a soldier's uniform to catch on fire. These are just some of the examples of what a laser could
do in a combat situation, but there are many more possibilities that you can build into your
simulations.
Because the energy absorbed by a target is influenced by several variables (laser wavelength,
surface material, surface finish), determining the amount of energy required to disable or destroy a
given target is really a case-by-case situation. However, Table 14-6 provides some general
energy-level damage guidelines that you can use in your game simulations.
6
The energy level
required to penetrate the steel armor of a tank would be considerably in excess of 10,000
J
/
cm
2
,
and there are no lasers in operation today that can meet that energy delivery requirement.
Table 14-6.
Laser Beam Damage Energy Levels
Required Energy Level, (
J
/
cm
2
)
Damage Type
Damage eye cornea.
1
Disable optical sensors.
10
Burn exposed skin.
15
Penetrate airplane metal skin.
700
Shoot down airplane or helicopter.
5000-10,000
Destroy missile.
10,000
