Abstract: A liquid-solid propulsion system having a tank of liquid oxygen and a high pressure chamber loaded with solid grain fuel with a portion of the liquid oxygen being passed through a heat exchanger to convert the liquid oxygen to gaseous oxygen. The gaseous oxygen is directed to the chamber or solid grain fuel to induce a fuel rich gas burn that is directed to a thrust chamber which also receives liquid oxygen to increase the characteristic velocity of the exhaust and thereby provide the specific impulse of the propulsion system. The gaseous oxygen is also directed to the liquid oxygen tank to pressurize the flow of liquid oxygen from the tank. Valves are interposed to control the flow of liquid and gaseous oxygen to provide the required mixture ratio in the thrust chamber for optimum specific impulse or to terminate the thrust of the propulsion system. A method for providing the liquid-solid propulsion system is also disclosed.