Radial pulse motor igniter-sustain grain

Abstract

A radial pulse rocket motor having a nozzle at the aft end includes longitudinally spaced hollow boost and sustain propellant grains in the combustion chamber thereof with an elongated tubular thermal barrier covering substantially the whole of the interior surface of the sustain grain to enable the production of separate boost and sustain pulses. At the forward end of the motor, mounted within a reentrant motor bulkhead position, is a multiple pulse arm-fire device which, when commanded, produces an igniting signal that is transmitted to a boost igniter for igniting the boost grain and a subsequent igniting signal that is transmitted to a sustain igniter for igniting the sustain grain. The sustain igniter is positioned in surrounding relation to the motor forward bulkhead reentrant portion, the multiple pulse arm-fire device, and the forward end of the tubular barrier, and comprises a consumable, molded, polyurethane case having two interlocking tubes with a thin 0.10 inch (2.5 mm.) wide annulus therebetween which contains a thin sheet of igniter propellant wrapped around and bonded to the inner tube. Upon completion of the burning of the boost grain and subsequent initiation of the sustain igniter, the operation of the sustain igniter produces a pressure of flaming gases externally of the forward end of the thermal barrier that is effective to turn the barrier inside out to expose the sustain grain to the flaming gases and to deposit the thermal barrier in the space previously occupied by the boost grain.