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Laser-heated rotating specimen autoignition testSpecimens of 440 C steel were rotated in a chamber pressurized with oxygen gas and heated with a 5-kW CO2 laser to determine the temperature required for autoignition to occur. Tests included exposures of static and rotating (25,000 rpm) specimens in oxygen pressurized to 5.51 MPa, and with focused laser fluences of more than 3.5 billion W/sq m. Specimen surface temperatures were monitored with a scanning infrared camera. Temperature measurement difficulties were experienced due to a problem with internal reflection inside the test chamber; however, posttest specimen examinations confirmed that surface melt (1371 C) was achieved in several tests. No sustained combustion was initiated in any rotating specimen. One static specimen was ignited. Results indicated that conditions necessary for autoignition of 440 C steel are more dependent on specimen geometry and available heat removal mechanisms. Sustained combustion occurred in the ignited static specimen with an estimated 130 C/sec cooling rate due to conduction. The rotating specimens could not sustain combustion due to a greater conductive/convective cooling rate of about 4000 C/sec and ejection of molten material. These results were applied to the Space Shuttle Main Engine (SSME) oxygen turbopump bearings to conclude that the LOX-cooled 440 C steel bearings cannot sustain combustion initiated by skidding friction.
Document ID
19880057445
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Au, A. C.
(Rockwell International Corp. Rocketdyne Div., Canoga Park, CA, United States)
Date Acquired
August 13, 2013
Publication Date
July 1, 1988
Subject Category
Chemistry And Materials (General)
Report/Patent Number
AIAA PAPER 88-2841
Accession Number
88A44672
Funding Number(s)
CONTRACT_GRANT: NAS8-40000
Distribution Limits
Public
Copyright
Other

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