NASA LogoNTRSNTRS - NASA Technical Reports ServerSearchmore_vertCollectionsAboutNewsHelpLogin Back to ResultsFeasibility Assessment of Thermal Barrier Seals for Extreme Transient TemperaturesThe assembly joints of modem solid rocket motor cases are generally sealed using conventional O-ring type seals. The 5500+ F combustion gases produced by rocket motors are kept a safe distance away from the seals by thick layers of phenolic insulation. Special compounds are used to fill insulation gaps leading up to the seals to prevent a direct flowpath to them. Design criteria require that the seals should not experience torching or charring during operation, or their sealing ability would be compromised. On limited occasions, NASA has observed charring of the primary O-rings of the Space Shuttle solid rocket nozzle assembly joints due to parasitic leakage paths opening up in the gap-fill compounds during rocket operation. NASA is investigating different approaches for preventing torching or charring of the primary O-rings. One approach is to implement a braided rope seal upstream of the primary O-ring to serve as a thermal barrier that prevents the hot gases from impinging on the O-ring seals. This paper presents flow, resiliency, and thermal resistance for several types of NASA rope seals braided out of carbon fibers. Burn tests were performed to determine the time to burn through each of the seals when exposed to the flame of an oxyacetylene torch (5500 F), representative of the 5500 F solid rocket motor combustion temperatures. Rope seals braided out of carbon fibers endured the flame for over six minutes, three times longer than solid rocket motor burn time. Room and high temperature flow tests are presented for the carbon seals for different amounts of linear compression. Room temperature compression tests were performed to assess seal resiliency and unit preloads as a function of compression. The thermal barrier seal was tested in a subscale "char" motor test in which the seal sealed an intentional defect in the gap insulation. Temperature measurements indicated that the seal blocked 2500 F combustion gases on the upstream side with very little temperature rise on the downstream side.Document ID19980219330Acquisition SourceLegacy CDMSDocument TypePreprint (Draft being sent to journal)AuthorsSteinetz, Bruce M.*(NASA Lewis Research Center Cleveland, OH United States)*Dunlap, Patrick H., Jr.*(Modern Technologies Corp. Middleburg Heights, OH United States)*Date AcquiredSeptember 6, 2013Publication DateJuly 1, 1998Subject CategoryMechanical EngineeringReport/Patent NumberNASA/TM-1998-208484AIAA Paper 98-3288E-11196NAS 1.15:208484Meeting InformationMeeting: PropulsionLocation: Cleveland, OHCountry: United StatesStart Date: July 12, 1998End Date: July 15, 1998Sponsors:Society of Automotive Engineers, Inc.,American Society of Mechanical Engineers,American Inst. of Aeronautics and Astronautics,American Society for Electrical EngineersFunding Number(s)PROJECT: RTOP 523-53-13Distribution LimitsPublicCopyrightWork of the US Gov. Public Use Permitted.Available DownloadsNameType19980219330.pdfSTIcloud_downloadcontent_copyvisibilityRelated RecordsThere are no records associated with this record.visibility_offNo Preview Available
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