The International Space

"Flow friction," a proposed ignition mechanism in oxygen systems, has proved elusive in attempts at experimental verification. In this paper, the literature regarding flow friction is reviewed and the experimental verification attempts are briefly discussed. Another ignition mechanism, a form of spontaneous combustion, is proposed as an explanation for at least some of the fire events that have been attributed to flow friction in the literature. In addition, the results of a failure analysis performed at NASA Johnson Space Center White Sands Test Facility are presented, and the observations indicate that spontaneous combustion was the most likely cause of the fire in this 2000 psig (14 MPa) oxygen-enriched system.

Electrical arc ignition is a concern for materials used in low pressure oxygen-enriched environments such as inside spacecraft. The National Aeronautics and Space Administration (NASA) Johnson Space Center requested that the NASA White Sands Test Facility conduct arc ignition tests to evaluate the hazard of electrical arc ignition of materials that could be in close proximity to batteries for the Constellation Program. Wire-break electrical arc tests were performed to determine the current threshold for ignition of generic cotton with a fixed voltage of 3.7 V, a common voltage for handheld electrical devices. These tests were performed in 34 % oxygen at varying pressures.

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ABSTRACT:The flammability in oxygen-enriched atmospheres of commercially pure (CP) titanium rods as a function of diameter and test gas pressure was determined. Test samples of varying diameters were ignited at the bottom and burned upward in 70 % O 2 /balance N 2 and in 99.5+% O 2 at various pressures. The burning rate of each ignited sample was determined by observing the apparent regression rate of the melting interface (RRMI) of the burning samples.The burning rate or RRMI increased with decreasing test sample diameter and with increasing test gas pressure and oxygen concentration.