The development of a safe, electrically-controlled extinguishable solid propellant (ESP) thruster would allow NASA to demonstrate an innovative throttleable solid rocket motor that could replace multi-mode liquid propulsion systems. Replacement of cold gas and monopropellant systems for in-space propulsion with a safe, volumetrically-efficient thruster set could offer game-changing improvements in performance. ESPs are inert unless ignited with an electric potential of appropriate magnitude. This project seeks to develop and demonstrate an electrically-controlled extinguishable solid rocket propellant using active electrode power to control propellant ballistics. One motor will be fired in a static test configuration. The motor will be subjected to numerous pulsed commands to demonstrate the ability of the propellant to throttle up and down, and will be extinguished. This motor throttling demonstration will use embedded grain electrodes and variable power supply to control the propellant burn rate and consequently the motor chamber pressure. The test motor will have a variable ratio throat (pintle) than can allow electrode-in-motor tests. The motor firing will demonstrate controllable, throttleable propulsion via electrodes using a minimum smoke (non-aluminized) propellant. The development test motor will be between one inch and five inches in diameter. The motor test firing will occur at the DSSP test range in Lovelock, Nevada. The ability to ignite and extinguish an ESP has been demonstrated using thrusters with a diameter of 0.125 inches. Larger motors have been made and tested, but testing has been limited to throttling (rather than extinguishment and re-ignition). Throttling is achieved by varying the voltage applied across the propellant. The use of an ESP thruster as a replacement for in-space liquid thrusters is presently at a Technology Readiness Level (TRL) of 2 or 3 based on the limited data on extinguishment and re-ignition. Demonstration of ignition, extinguishment, and re-ignition of a one-inch to five-inch diameter motor will constitute component and/or breadboard validation in a laboratory environment, thereby bringing the ESP technology to a TRL of 4 for in-space propulsion. The development of a controllable extinguishable solid propellant clearly supports MSFC's strategic emphasis area of propulsion systems. Specifically, this technology addresses the needs of the technology theme entitled Advanced In-Space Propulsion Tech.