GB1480723A - Dual area solid propellant rocket nozzle - Google Patents

Abstract

1480723 Solid fuel rockets: propulsion nozzles ROCKWELL INTERNATIONAL CORP 6 May 1971 13544/71 Heading F1J [Also in Divisions F3 and F4] A solid propellant rocket having boost and sustain grains is provided with a fixed convergentdivergent nozzle and a movable convergentdivergent nozzle, the latter being operable in response to a pressure drop to a predetermined level in the combustion chamber occurring during burning of the boost grain, to block a portion of the throat areas of the nozzles and increase the combustion chamber pressure during burning of the sustain grain. In one embodiment, Fig. 1, the aft end of the rocket casing 11 houses a boost propellant grain 13, a combustion chamber 16, and an exit nozzle section 17 having the configuration of a convergentdivergent nozzle. The section 17 can be made of asbestos- or silica-reinforced phenolic resin and have a graphite insert 19 forming the nozzle throat. Upstream from the section 17 is a hollow nozzleforming movable body 21 having a convergentdivergent throat section 22 and formed of graphite or a reinforced plastic. The outer wall 23 of the movable body 21 has a surface 27 which will act as a seal against the forward convergent surface 25 of the nozzle section 17. Disposed within the section 17 is at least one, and preferably three or more, housings 28 which serve as cylinders for pistons 29. Each piston 29 is fixed through a rod 30 to a support arm 31 secured to the movable body 21. Hydraulic fluid within each housing 28 prevents normal movement of the piston 29 from its forward position, as shown. Connected to each housing 28 is an outlet line 35 and an explosivelyactuated servovalve 37, the latter being actuated by means responsive to a drop to a predetermined pressure level within the combustion chamber, Fig. 7 (not shown) to release the fluid from the housing 28 through a dump port, the force of the combustion gases then moving the body 21 towards a closed position. Initially the movable body 21 is in an open position, permitting the gas to flow through its nozzle section as well as around the body and between it and the nozzle section 17, as shown by the arrows. The combined area of these two nozzle areas is greater than that of the throat insert 19 of the nozzle section 17, thus allowing the latter to govern the chamber pressure. In an alternative embodiment, Fig. 3, an internal body 53 is shaped about its outer periphery so as to form with a portion 51 disposed in the aft end of the rocket casing 47 a first annular convergentdivergent nozzle 57. The body 53 is permanently supported by struts 55, and has a second convergentdivergent nozzle 59 formed within it. Just upstream of the annular nozzle 57 is disposed a torus-shaped, movable body 61. In the open position shown, the gases from the boost grain 49 flow, as shown by the arrows, around the torus and through the throat portion of the first nozzle 57, as well as through the second nozzle 59. Actuating means 63 are essentially the same as those in the first embodiment.