Game Development Reference
In-Depth Information
Figure 11-4.
Gravitational acceleration as a function of altitude
Drag
By this point in the topic, you should be very familiar with the concept of aerodynamic drag
and with the equation that is used to evaluate drag. Just to refresh your memory, the drag expe-
rienced by a rocket as it travels through the atmosphere is proportional to the atmospheric
density, the square of the velocity, the frontal area of the rocket, and the coefficient of drag for
the rocket.
1
2
2
FCv A
=
r
(11.14)
D
D
Unlike most of the vehicles, balls, and projectiles we have been exploring in this topic,
altitude effects must be included when evaluating the drag of a rocket. If a rocket ascends into
the upper atmosphere or into outer space, the density value will change by several orders of
magnitude during the ascent. The density at any altitude can be computed using the
USatm76
class that was discussed earlier in this chapter. Figure 11-5 shows the variation of density with
altitude up to an altitude of 84
km
.
