Evaluation of Solid Propellant Burning Rates
Solid propellant burning rate is a fundamental characteristic and the metric commonly chosen to evaluate the performance of any propellant composition. In relation to the aerospace industry, solid propellants are burned in a laboratory setting at different pressures reminiscent of those seen in real rocket motors, and the resulting of burning rates are plotted as a function of pressure. According to Biblarz and Sutton [5], burning rate and pressure are related by a power function (called propellant power law) Equation 1, which is also known as (Saint Robert’s Law). r_b=a.P^n……………………(1). Where, rb : is the burning rate,
P: is the test pressure, a: is the experimentally constant known as the temperature coefficient, n: is the burning rate exponent or pressure index.

A linear relationship fitted to Equation 1 (illustrated in Figure 2) for a typical propellant formulation, when the burning rate is plotted as a function of pressure on a log-log scale.

Figure 2: Burning rate and pressure linear relationship.

AP oxidizer composite solid propellant plays a pivotal role in influencing the burning rate due to its particle size, concentration and combinations of particle sizes utilized. The loading of AP by percent mass (αox) influences oxidizer-fuel ratios which …show more content…
Tailoring involves varying the oxidizer particle sizes, binder ingredients, or additives to alter the burning rate behavior in response to pressure in order to meet a certain mission objective. In Figure 6, the baseline burning rate is modified to become more and less pressure sensitive (blue and red), and this tailoring corresponds to changing the value of n in Equation 1; altering the magnitude of the burning rate although retaining the same pressure sensitivity (gray) corresponds to changing the value of