Laser Ignition of Nitramine Composite Propellants and Crack Propagation and Branching in Burning Solid Propellants

Two major tasks performed during the report period of investigation were: (i) laser ignition of nitramine-based composite propellants using a high- powered CO2 laser in (ii) crack propagation and branching in burning solid propellants. The laser ignition of a series of RDX-based composite propellants was studied theoretically and experimentally. A comprehensive model for the radiative ignition of the nitramine composite propellants was formulated. The theoretical model was solved numerically. A radiative ignition test setup employing a high-powered CO2 laser was designed and constructed to study ignition characteristics of a series of RDX-based nitramine composite propellants. Interactions between the infrared laser beam and nitramine composite propellants revealed a number of interesting processes. The laser ignition of composite propellants involves many complex thermophysiochemical processes including gasification, initiation of a luminous flame, propagation of the flame, and chemical reactions near the sample surface as well as heat conduction in solid phases. In general, the delay time based upon the onset of light emission decreases monotonically with the increase of incident laser energy flux. Keywords:Ignition, Carbon dioxide laser, Nitramine, Composite propellants, Thermal decomposition, Reaction mechanisms, Ignition delay, Radiation ignition, Crack propagation, Crack branching, Interrupted burning, Depressurization, Extinguishment.