Abstract: A controlled fuel flow system from variable flow solid fuel gas generator to secondary combustor is provided, which system includes a hot gas valve which is operated by an electronic controller. The valve is mounted between the gas generator and the secondary combustor, which valve has in the throat thereof a pivotable blade that moves to relatively blocking and unblocking positions therein and a nozzle downstream of such blade which communicates with the secondary combustor. A first pressure transducer is mounted in the gas generator and a second pressure transducer is mounted downstream of such blade near or in the nozzle. Actuator means are also provided to pivot such blade between relatively blocked and unblocked settings as guided by electronic gas flow controller logic. The secondary combustor has one or more air ducts therein and the above system is mounted, e.g., in a variable flow ducted rocket.