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Cite this document
The liquid oxygen (LOX) reactivity results using the ambient pressure LOX mechanical impact test did not yield reproducible results for halogenated (precision cleaning) solvents tested at the Johnson Space Center (JSC), the White Sands Test Facility (WSTF), and at the Marshall Space Flight Center–Materials Combustion Research Facility (MCRF–MSFC) to replace the precision cleaning solvent, HCFC 225 (AK225). The ambient pressure LOX impact testing is established in the ASTM G86-98 test method and is specified by Test 13A in NASA STD 6001(B). In this test method, a known amount of energy is transferred from a free falling plummet to a striker pin resting directly on the test specimen immersed in LOX. The WSTF impact tester produced higher reactivity rates at lower energy levels for the same tests performed at MSFC. This indicates factors other than total input energy to the sample influence the materials reactivity in LOX. Penetration (calibrated) drop tests were performed at WSTF and MSFC. The penetration drop tests provide a simple and reliable method for verifying impact energy, but this method does not provide a measurement of other factors that may contribute to the material’s sensitivity to impact reactions. This paper discusses the interaction of factors that are not clearly addressed in the ASTM G86-98 test method and that should be an important focus of attention. Many variables were examined, including percent of relative humidity during sample preparation, the use of the plummet (rebound) catcher, variability of sample preparation at each facility, and impact testing with and without the insert disks. These and other variables attribute to the wide differences in reactivity. More standardization and controls in the test protocol, along with further testing and improvements, are recommended. It is hoped that the insight and observations of the NASA independent assessment (IA) team will provide useful support and discussions for improving the standard test method that is used for ambient pressure LOX impact testing.
liquid oxygen (LOX) mechanical impact, repeatability, halogenated solvents, edge reaction, rebound impacts, ignition
Ross, H. R.
A2 Research JV., NASA Stennis Space Center (SSC), Gas & Materials Science, MS
Gentz, S. J.
NASA Engineering and Safety Center (NESC), NASA Marshall Space Flight Center, Hunstville, AL