Flame response of solid propellant AP/Al/HTPB to a longitudinal acoustic wave

This paper is devoted to an experimental work which consists of the analysis of the flame of a small solid propellant sample, AP/Al/HTPB, subjected to a longitudinal acoustic wave. Experiments were conducted in a closed tube under two mean pressures: 1 and 2.5 MPa. The qualitative and quantitative analysis of the flame snapshots, using a microscope and a high-speed camera, revealed that the acoustic wave created at the end of the chamber by a pulser system strongly affects the flame and the combustion products dynamic above the solid propellant surface, namely, the flame and the hot products oscillate around a line perpendicular to the propellant surface. This dynamic of the hot gas disturbs the local burning rate and the regression surface profile. Thus, the thrust and the burning duration will change, therefore, the flight path of the rocket may shift and can lead to failure of the mission.