Topic summary
Solid rocket
Extracted from the Wikipedia article Solid-propellant rocket.
Grain geometry
Solid rocket fuel deflagrates from the surface of exposed propellant in the combustion chamber. In this fashion, the geometry of the propellant inside the rocket motor plays an important role in the overall motor performance. As the surface of the propellant burns, the shape evolves (a subject of study in internal ballistics), most often changing the propellant surface area exposed to the combustion gases. Since the propellant volume is equal to the cross sectional areaAs times the fuel length, the volumetric propellant consumption rate is the cross sectional area times the linear burn rate ḃ, and the instantaneousmass flow rate of combustion gases generated is equal to the volumetric rate times the fuel density ρ: