Initiating Reaction in Liquid Propellants by Focused Laser Beams

Abstract

Droplets of HAN-based propellants were exposed to initiation by focused ruby laser beam pulses and the extent of decomposition at atmospheric pressure was monitored by accurate measurement of the permanent gas volume generated. Apart from the practical objective of laser ignition, the method allowed the effect of various forms of preactivation to be studied. This included precursory electrolysis, preheating and dyeing of the liquid, as well as incorporation of various species in the gaseous plasma generated by focusing the beam in various media just outside the droplet. It is shown that prcactivation-e.g.,by precursory electrolysis-leads to substantially increased decomposition and that the various methods of presensitising the liquid propellants are cumulative only up to a common maximum. Beyond this. the dominant influence is the constitution of the gaseous plasma, with the inclusion of oxides of nitrogen producing the major effect. These observations are discussed in relation to both their underlying chemical mechanism, and their practical applicability.