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Many materials will ignite or initiate high energy reactions when in contact with gaseous oxygen (GOX) or liquid oxygen (LOX) if subjected to stimuli such as a mechanical impact, adiabatic compression (pneumatic impact), or an electrical discharge in the form of a spark. Such materials must therefore be characterized as to compatibility with LOX or GOX to define the degree of hazard with their use.
Generally, materials are more sensitive to mechanical impact in gaseous oxygen than in liquid oxygen, and impact sensitivity is known to increase with increasing pressure. Thus, the evaluation of the sensitivity of materials in GOX is required to supplement LOX impact test data.
Three independently developed high-pressure GOX mechanical impact testers have been used to evaluate materials for the space shuttle program. This paper presents a description of a test program evaluating the performance of these three high-pressure oxygen mechanical impact test systems. Two of the systems were fabricated from the same design drawing, whereas the third system, even though similar, was of different design. Four unpressurized mechanical LOX impact testers were also evaluated.
The most suitable materials identified were Teflon® TFE for gaskets and seals, Krytox® 240AC grease as a lubricant, and the fluorocarbon elastomers where a rubber is absolutely necessary.
oxygen compatibility, mechanical impact, hazards, fire, flammability, minimum impact energy
John Space Center, National Aeronautics and Space Administration, Kennedy Space Center, FL