Abstract: Systems and methods of controlling solid propellant burn rate, propellant gas pressure, propellant gas pressure pulse shape, and propellant gas flow rate, rely on the position of a throttling valve. A throttling valve that is movable to a control position is disposed downstream of, and in fluid communication with, a solid propellant gas generator, and in parallel with a plurality of reaction control valves. The solid propellant in the solid propellant gas generator is ignited, to thereby generate propellant gas. The throttling valve is moved to a control position to attain a desired solid propellant burn rate, propellant gas pressure, and/or propellant gas pressure pulse shape.