Patent ID: 6968673

Claim:
An external combustion cool gas generator comprising: a first storage tank configured to contain a high-pressure liquid propellant; a second storage tank configured to contain a reactive chemical; a combustion chamber connected to the second storage tank and configured to chemically react the reactive chemical to form a hot product gas at a pressure substantially lower than a pressure of the high-pressure liquid propellant; a nozzle having a melting temperature; a heat exchanger connected to the first storage tank at a first end and connected to the nozzle at a second end, the heat exchanger configured to plumb the high-pressure liquid propellant from the first storage tank to the nozzle, wherein the heat exchanger is connected to the combustion chamber so that heat from the hot product gas is transferred to the high-pressure liquid propellant through heat-conducting walls of the heat exchanger to thereby raise a temperature of the high-pressure liquid propellant to substantially gasify the high-pressure liquid propellant, wherein the nozzle is configured to expel the substantially gasified high-pressure liquid propellant from the gas generator and, during the expulsion, to expand the substantially gasified high-pressure liquid propellant, and wherein the gas generator is configured so that an expansion temperature of the substantially gasified high-pressure liquid propellant to be expanded by the nozzle is substantially lower than the melting temperature.