A rocket is a machine that moves through the ejection of a supersonic gas flow at high temperatures. The rocket can have two types of propellant, can be both liquid and solid, and various chemical compositions. Liquid propellant engines need two components: the fuel and the oxidizer. In the solid propellant rocket motor, the propellant is stored inside the combustion chamber in the form of a propellant grain. After ignition the propellant is consumed to the end, due to this, it is not possible to control the burning of the propellant, and considerable variations in the pressure can occur, resulting in combustion instabilities, when certain frequencies are reached. Therefore, the general objective of this work is to study the stability of the KNSU propellant. The methodology found in the literature was used. Thus, we characterized the propellant frequency range and frequency response function. As a result, the frequency response function curves for the KNSU were obtained and identified the frequency range at which instability occurs.