Redesigned solid rocket motor case-to-nozzle joint development

Abstract

The case-to-nozzle joint in the Space Shuttle solid rocket motor is designed to provide thermal protection to the case and nozzle metal parts and to the O-ring seals during motor operation and subsequent heat soak. As a part of the redesign effort, several design improvements were incorporated into the joint configuration. These included an unvented bonded joint, the addition of a pressure-actuated flap gap next to the bondline, the addition of an adhesive wiping O-ring, and the addition of 100 bolts in the radial direction to restrict joint movement. With the new design features, it became necessary to develop a new nozzle installation procedure. Also, a number of hot-fire static tests were performed before the joint could be used in a flight motor. In several of these tests, flaws were deliberately placed in the case-to-nozzle bondline and O-rings to determine how the redesigned joint would function with a portion of the redundant sealing system disabled prior to motor operation. Each flaw condition tested was accompanied by a flow/thermal analysis. Once these analyses had been verified, analyses were then used to examine other flaw configurations that were not being tested.