Energetic material combustion studies on propellant formulations and its components such as AP, ADN, HMX, RDX, TNAZ, NTO and CL-20 have been performed. The propellant formulations examined contained ADN as the oxidizer (in single crystal and "prill" or spherical form). The overall performance of the formulation was found to be sensitive to the microstructure of its oxidizer component. Combustion experiments where the ignition of the propellant is filmed at the highest magnifications inside an ESEM (Environmental Scanning Electron Microscope) show that "hiccups" or "micro-explosions" of the formulation components are providing local increases in the burn rate. Such localized events may form a contribution to the observed instabilities.