Ignition, Combustion, and Curing Characteristics of Direct Ink Written Dual-Cure Electrically Controlled Solid Propellants

High Resolution Image Download MS PowerPoint Slide This study explored the direct ink writing of electrically controlled solid propellants using an ultraviolet and thermally curable binder based on poly(ethylene glycol) diacrylate. This work presents the first known fabrication of an electrically controlled solid propellant using additive manufacturing techniques, as well as the first example of an electrically ignited solid propellant with ammonium perchlorate as the sole oxidizer. Ammonium perchlorate and lithium perchlorate propellants with carbon black additive concentrations from 0 to 5 wt % were formulated and investigated to determine the influence of the additive on curing properties. Thermal decomposition, ignition delays, and burning rates were investigated for propellants containing 2.5 wt % carbon black. Cure depth results revealed diminishing cure depths with increasing carbon black concentrations due to UV absorption by carbon black. The cure depths of propellants ranged from 0.18 to 4.68 mm. Ignition delay experiments exhibited an inverse relationship between ignition delay and applied voltage for the lithium perchlorate propellant and no voltage dependence of the ignition delay for the ammonium perchlorate propellant. The ammonium perchlorate propellant showed considerably lower ignition delays compared to those of the lithium perchlorate-based propellant at all voltages. The lithium perchlorate propellant demonstrated significant ignition delay sensitivity with print orientation, while the ammonium perchlorate propellant did not. Pressurized combustion experiments demonstrated the capability to throttle the burning rate of lithium perchlorate propellant by changing the voltage magnitude and illustrated higher burning rate sensitivity to voltage rather than pressure.