
79Analytic and Computational Ballistics
Again, since the base of our projectile is at location x and the local pressure on the base is
p
S
, we can substitute these values into Equation 3.46 for x
g
and p to obtain
p
x
S
constant=− +
(3.64)
Remember that this is a local condition that we applied to the gas in the vicinity of the base
where the gas’s mass center is approximately at x.
Following the same procedure that we used to arrive at a general expression for pres-
sure, but now with bore resistance, we rearrange Equation 3.64 to nd the constant of
integration, and with simplication arrive at
constant = +
S
p
x
(3.65)
If we use Equation 3 ...