Speed control of a missile with throttleable ducted rocket propulsion

Abstract : The wide range of altitudes, in which many missiles must be operational, makes the variation of thrust mandatory and leads ultimately to the control of propellant mass flow. With the choice of a solid propellant ducted rocket as propulsion system, the gasgenerator must produce a variable mass flow rates. The widely applied method uses a propellant with a pressure sensitive burning rate. A valve with variable throat area controls the mass flow out of the gasgenerator. This report describes a mathematical model of the controller design. The Mach number controller computes the suitable nominal value for the gasgenerator pressure while accounting for the pertinent gasgenerator dynamics. This procedure requires the knowledge of the pressure sensitive burning rate with adequate narrow tolerance limits. In case of high-g flight manoeuvers the system can optionally switch over to a simple command for the pressure nominal value. An adaptive controller is nested within the Mach number loop to keep the gasgenerator pressure in closed loop control. Thus, an open loop control of the mass flow rate is provided. This loop is controlled by the flight Mach number loop, its value being derived from flight data.