Diode Laser Ignition Mechanism for Hybrid Propulsion Systems

A novel diode laser-based ignition technique for hybrid propulsion systems has been developed. In an effort to determine the physical ignition mechanism, a test series was conducted in an optically accessible, slab-burning combustion chamber. High-speed imaging of the ignition event has revealed that high-temperature carbon particles created during laser-induced flash pyrolysis of the solid fuel grain act as the carriers of ignition energy. Tests run on both charring and noncharring thermoplastic fuel candidates support this observation. In this paper, an initial theory of the ignition mechanism is developed; and supporting evidence collected from tests in both oxidizing (oxygen) and inert (nitrogen) flow environments is presented. Finally, a number of observations regarding the effects of oxidizer velocity and incident laser power on ignition delay are discussed.