Abstract
An experimental study of combustion behavior of polyethylene insulated wires in quiescent atmosphere has been performed in microgravity to obtain fundamental data of burning characteristics of wire insulation for fire safety in space. Four samples with different insulation thickness, 0.075-0.5 mm, and the same wire diameter, 0.5 mm, were investigated. The effects of ambient oxygen concentration, wire initial temperature, insulation thickness, and type of diluents, including He, Ar, N2, and CO2, were examined in the microgravity experiments. The results show that flame configuration and flame spread rate in microgravity change strongly depending on ambient oxygen concentration . It was indicated that flame spread rate decreases with increase in insulation thickness. In addition, decrease rate of flame spread rates as a function of wire insulation thickness appears to be smaller with larger insulation thickness. Flame goes out at highest oxygen concentration with He diluted
atmosphere among the four dilution gases under microgravity. Also, it was observed that CO2 diluted atmosphere increases flammability of polyethylene insulated wires in microgravity compared with normal gravity.
