Thiokol Corporation

Donald V Lushis

Victor Singer

Frank S Inman

Thomas J Kirschner, Jr

Donald C Giedt

A braided preform fabrication for annular refractory articles such as an integral monolithic throat section and exit cone of a rocket motor nozzle is formed on a mandrel and includes closely spaced radially oriented carbon rods that extend to a uniform length from the mandrel surface and carbon fibers braided on the surface of the mandrel around the carbon rods in a triaxial braid whereby the fabrication has a 4-D fiber architecture. The density of the fabrication is increased by a process that is repeated four times and involves the steps of vacuum impregnation thereof with pitch, subjecting the impregnated preform to high pressure at a temperature that is gradually increased to about 700.degree. C. to convert the pitch to coke and to form the braided preform and mandrel into a billet, and producing graphitization of the braided preform by subjecting the billet to an argon atmosphere in a vacuum furnace at a temperature that is gradually increased to 2,500.degree. C. The mandrel is usually removed from the billet by machining after the second repetition of the process, but it may be removed at any time after the braided preform structure has acquired sufficient strength to withstand the temperature and pressure of further processing.

Braided preform for refractory articles and method of making

A thrust reversal system for reducing, neutralizing and/or reversing the thrust vector resultant of a solid propellant rocket motor utilizes a movable conical piston or plenum cover that fits over a plurality of small ports that are arranged in a circumferential band around the aft dome of the rocket motor. Before actuation, the cover seals the ports. When actuated, the cover is retracted aft a pre-set distance to uncover the ports, shock and the stroke time being controlled by a shock absorber which in one embodiment of the invention is of the hydraulic type and in other embodiments is of the mechanical type. The cover becomes a baffle which directs the combustion chamber gas exiting the ports outward and forward. Suitable control of the flow characteristics may be exercised by the setting of the travel distance of the piston cover and the number, size and orientation of the ports. The time to reach a negative thrust vector can be reduced by increasing the size of the hydraulic fluid control orifice or by the use of high rate stroke mechanical shock. The amount of reverse thrust may be increased by optimizing the reversal port area and the reversal nozzle angle.

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Newark, DE, United States of America

Donald V Lushis