Using a Burning Rate Emulator to Analyze Flame Extinction Time on the International Space Station

Abstract

There is limited understanding of the fire hazards of liquids and solids in microgravity conditions. As interest in space exploration increases, the need to understand these hazards within spacecraft is of paramount importance. As one of NASA’s Advanced Combustion in Microgravity Experiments, the Burning Rate Emulator (BRE) is used to improve the fundamental understanding of material flammability in microgravity, including the conditions that affect extinction behavior. Oscillation onset and extinction times were measured for emulated flames burning gaseous ethylene and methane diluted with varying amounts of nitrogen using porous 25 and 50 mm BRE burners aboard the International Space Station. Tests were performed with varying fuel flow rates, oxygen mole fractions (XO2) ranging from 0.21-0.4, and pressures ranging from 0.57-1 bar. Relationships between the extinction times and the various experimental parameters were explored to determine what conditions produce longer lasting flames. The measurements are reasonably well correlated by scaling the oscillation onset and extinction times with XO23 Re–0.5, where Re is the jet Reynolds number. These times decrease with increasing burner diameter but are independent of pressure. This is further support of the significant hazards of using enriched oxygen atmospheres in spacecraft.