Experimental Study of Flame Balls in Space: Preliminary Results from STS-83

Results from the Structure Of Flame Balls At Low Lewis-number (SOFBALL) spaceflight experiment conducted on the STS-83/MSL-1 Space Shuttle mission are reported. These are the first premixed gas combustion experiments to be performed in space. Two of the 15 scheduled tests were successfully completed on this shortened mission. Two different types of mixtures were burned, and both burned much longer than expected based on prior theoretical understanding. From these tests, two new insights were obtained, namely, on the buoyancy-induced drift speed and repulsion of adjacent flame balls due to their mutual interaction. Preliminary results from the STS-94/MSL-1 reflight are also presented and show a remarkable sensitivity of the flame balls to small accelerations resulting from Orbiter attitude control maneuvers. Comparison of experimental results to computational predictions reveals limitations in current models of H 2 -O 2 chemistry for very lean mixtures. It is shown how the results of these space experiments may provide an improved understanding of the interactions of the two most important phenomena in combusting materials, namely, chemical reaction and transport processes, in the unequivocally simplest possible configuration.