Solid propellant rocket motors are simple, easy for handling, and ready for immediate operation. That is why they are the preferred rocket motors in multiple applications and missions. However, in practice, solid propellant motor thrust cannot be controlled once the propellant has been ignited. The thrust developed during operation depends on the propellant burning surface and burning rate. The burning surface may change according to a predesigned geometry of the propellant grain, but cannot be actively controlled during the propellant combustion. This research investigates the possibility of controlling the burning rate by applying electric field/voltage.
Common ammonium perchlorate (AP) based propellant were found to be insensitive to electric field. However, the research revealed that ammonium nitrate (AN) based propellants are sensitive to electric effect, and their burning rate can be controlled by applying voltage on the propellant. These findings are promising for better managing the energy and maneuverability of tactical motors, as well as for small space motors, where such electric controlled solid motors may replace the traditional hydrazine motors, whose use is projected to diminish and even to be banned due to the hydrazine carcinogenic and toxic properties.
An experimental system has been designed, constructed and tested. The experiments investigated the effect of voltage (up to 250V) for different values of oxidizer mass fraction, strand thickness, storage condition, and pressure, demonstrating 3-5 fold increase of the burning rate when increasing the voltage from 70 to 200V. A theoretical model showed good agreement with the experiments.
