Abstract: Method and device for continuously and automatically maintaining optimal control settings for rich fuel gas generation within the pre-starting, starting, and operational modes of a ducted solid fuel rocket motor, through actual or potential control of pressure within a fuel rich gas generator by use of a temperature sensitive hydraulic/mechanical choke, the mechanical component of which comprises an expansion bellows endwise attached to a spring-biased slidable nozzle valve throat blockage element, and the hydraulic component comprises a temperature-sensitive constant volume fluid reservoir, or its equivalent.