Burning in microgravity: Experimental results and analysis

Abstract

Burning experiments are analyzed for 59 successfully ignited tests using a gas burner (BRE) to emulate the steady burning of 25 mm diameter flat surface materials. More than half of the tests resulted in long burns of at least 2 and as long as 5 min. Mixtures of ethylene and nitrogen allow for 23.6 and 47.2 kJ/g heats of combustion (LHV). Nominal ambient conditions range from 40% to 21% oxygen and pressures of 1 to about 0.56 bar. NASA human habitat atmospheres have been used. Generally, it has been found that nominal oxygen mole fractions of 26% and above can allow steady flames. The flames are thin blue in color and grow slowly over time for minutes. Some self-extinguish, some had periodic oscillations, and others appear to have become steady and were shut down. Theoretical analyses show the shutdown flames were steady in growth, and all of the test endpoints were more than 94% of steady state in flame heat flux. Flame heat flux for set mass flux allowed the estimation of heats of gasification to relate to steady solid materials that might burn in microgravity. Radiometers allowed the computation of flame radiative fraction that appeared to correlate well with the measured flame height. Results are shown for heat flux, flame height and base radius, radiative fraction as a function of fuel mixture mass flux, and various oxygen and pressure atmospheres.