
42 Ballistics: Theory and Design of Guns and Ammunition
surface area decreases affects this relationship. The simplest model for the relationship
between burn rate and pressure is given by
D
B
=−
β
(2.98)
where
D(df/dt) is the time rate of change of the web (i.e., the burning rate)
β is a burn rate coefcient
p
B
is the pressure (we will discuss the subscript later)
The negative sign comes about because the amount of propellant would be increasing if
D(df/dt) were to result in a positive number. This simple relationship facilitates our analy-
sis of propellant behavior in a gun. Other relationships can more accurately describe pro-
pellant behavior ...