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Fuel Combustion in Microgravity

Fuels burning in space behave very differently than they do on Earth because of the absence of gravity. The Flame Extinguishing Experiment (FLEX) examines the combustion of liquid fuel droplets on the International Space Station.

The Flame Extinguishment Experiment (FLEX) examines the combustion of fuel droplets burning inside the Combustion Integrated Rack (CIR) aboard the International Space Station (ISS). The goal is to map the flammability boundaries for liquid fuel combustion in reduced gravity to quantify the suppressant effectiveness of various gaseous agents over the range of candidate spacecraft atmospheric pressures and oxygen concentrations. Detailed spatially and temporally resolved measurements of droplet burning rate, flame extinction, flame radiation, soot concentration, and soot temperature are obtained. Using these data, predictive theoretical and numerical codes and chemical kinetic schemes are refined to model flammability boundaries as a function effective gravitational acceleration. There are several important 1-g applications as well, including the development of improved and validated reduced (simplified) theoretical and numerical sub-models of important physical processes (chemical kinetics, radiation, soot formation/destruction) that can be used in simulations of large scale, realistic fires.

During FLEX on-orbit operations, experiment conditions are established, the fuel droplet is dispensed, ignition is achieved, and data is recorded. After the data is retrieved from the ISS, video records are produced and all the data is disseminated to NASA scientists and researchers at USRA's National Center for Space Exploration Research (now known as Advanced Research Associates). Furthermore, the data is analyzed using image enhancement and tracking software to yield the burning rate and flame dimension data as a function of time.