Upward Flame Spread over a Thin Composite Fabric: the Effect of Pressure and Microgravity



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48th International Conference on Environmental Systems


The influence of the environment on the flammability of combustible solid materials is of utmost importance for applications where fire safety must be ensured. Such is the case of spacecrafts vehicles where a fire could be catastrophic, and the environmental conditions can greatly differ from what is encountered on earth. Moreover, experimental testing under these conditions can be difficult and expensive, with limitations in sample size and duration. Reducing buoyancy by decreasing ambient pressure is a possible approach to simulate a spacecraft environment, thus facilitating testing. The objective of this work is to obtain information on the effect of pressure on the flammability of a thin material, and by comparison with microgravity data, determine up to what point reducing pressure can be used to simulate reduced gravity. Specifically, this work studies the effect of pressure and microgravity on upward/concurrent flame spread rates and flame appearance of a burning thin fabric sample made of 75% cotton and 25% fiberglass. Experiments in normal gravity were conducted using pressures ranging between 100 and 30 kPa and a forced flow velocity of 20 cm/s. Microgravity experiments were conducted during NASA's Spacecraft Fire Experiment (Saffire), on board of the Orbital Corporation Cygnus spacecraft at 100 kPa and an air flow velocity of 20 cm/s. Results show that reductions in pressure slow down the flame spread over the fabric. As pressure is reduced, flame intensity is also reduced, until eventually a very weak blue/purple flame was observed for the lower pressure tested. Comparison with the flame spread rates in microgravity show that similar flame spread rates are obtained at around 30 kPa. The results of this work provide information about the similitudes of the flame spread process in low pressure and microgravity environments, providing guidance for potential ground-based testing for fire safety design in space exploration.


Maria Thomsen, University of California, Berkeley
Carlos Fernandez-Pello, University of California, Berkeley
David Urban, NASA
Gary Ruff, NASA
Sandra Olson, NASA
ICES509: Fire Safety in Spacecraft and Enclosed Habitats


Flame spread rate, low pressure, microgravity, environmental conditions, Sibal