Reverification of Techroll Seal Used in the IUS (Inertial Upper State) Nozzle,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HUNTSVILLE AL GEORGE C MARSHALL SPACE FLIGHT CENTER
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The Inertial Upper Stage IUS uses a Techroll Seal in the nozzle design of each of its two solid rocket motors. As a result of the small Solid Rocket Motor SRM-2 anomaly of the STS-6 space shuttle flight, additional seal testing, motor firings, and structural analyses have been conducted. This paper begins with a background of the nozzle configuration, followed by a description of the design features of the Techroll Seal, and concludes with the post-flight seal testing, motor firings, structural analysis, and design changes. Although the Techroll Seal which is constructed of two plies of Kevlar, sandwiched between layers of neoprene, was designed and qualified prior to flight, a significant amount of highly instrumented testing and analysis has been accomplished since the flight anomaly. The additional analysis and testing shows the significant effects of the nozzle gimbal angle and the increase in seal temperature due to gas leakage and pyrolysis gas. It was learned that the critical design condition for the seal occurs much later in the motor burn than at the time of maximum chamber and seal pressure, as concluded in the original design analyses.