A method for generating electric power for a rocket system includes burning a primary solid propellant grain to create a primary high pressure gas for providing thrust to the rocket, opening a first valve to divert a portion of the high pressure gas to an auxiliary solid propellant grain for igniting the auxiliary solid propellant grain, wherein the auxiliary solid propellant grain is disposed in a housing separate from the primary solid propellant grain, and burning the auxiliary solid propellant grain to create an auxiliary high pressure gas for turning a turbine. The method further includes driving a generator with the turbine and generating an electric power with the generator.