Abstract: A gas-generating agent for use in a ducted rocket engine essentially consists of an aliphatic polyester represented by the formula: ##STR1## or the formula: ##STR2## and a curing agent and optionally incorporating therein additives such as a curing catalyst.

Abstract: To quickly change rocket flight direction immediately after a rocket has been launched without increasing the wing area, the rocket flight direction control system comprises four steering wings for controlling rocket flight directions; four deflectable nozzles for jetting combustion gas backward to generate rocket thrust; a controller for generating steering control signals; and at least one actuator for actuating the deflectable nozzles in response to the steering control signals in synchronism with steering motion of the steering wings. Further, when the deflectable nozzle is divided into two, fixed and movable, nozzles, the diameter of the outlet end of the fixed divergent nozzle of the overexpansion type nozzle in matched with that of the movable nozzle for prevention of gas leakage through a gap between the two nozzles.