CHARACTERIZATION OF SMOKE PARTICLES GENERATED IN TERRESTRIAL AND MICROGRAVITY ENVIRONMENTS

Smoke produced by the pyrolysis of fluorinated wire insulations is cha racterized to partially provide the data base required to conduct a co mprehensive Probabilistic Safely Assessment (PSA) of future human-crew ed spacecraft. The smoke is assessed via measurements and observations regarding the size, morphology and elemental composition of the gener ated particulate matter. Of particular interest is how the microgravit y generated aerosols affect the design of future on-board detection an d suppression systems. Analyses of the particles generated from short lengths of overheated wires insulated with Tefzel or Teflon (modified forms of ethyltetrafluorethylene) were performed with the aid of trans mission electron microscopy and energy dispersion spectroscopy. Result s from short-duration microgravity tests in the NASA Lewis drop tower indicate that the sizes of the primary particles vary depending on the corresponding gravity environment within which they were produced. Te fzel particles produced in microgravity were found to be approximately twice as large as those produced in normal gravity. However, the morp hology appears to be gravity independent and material dependent. Clust er formations for both gravity environments are composed of long linea r chains of particulate matter. Additionally, a chemical composition a nalysis for both fluoropolymer insulations suggests that the particula te elemental composition is also independent of the gravity environmen t. (C) 1997 Published by Elsevier Science Ltd.