A gaseous combustible mixture from the pyrolysis of solid fuel and oxygen from the ambient
environment establishes a diffusion flame over the fuel surface. This diffusion flame sustains and
spreads over the solid material by the heat transfer from the flame to the unburnt solid ahead of the
flame. The absence of buoyancy-induced flow in microgravity makes fire in spacecraft behave very
differently from that of normal gravity on the earth. The study of flame spread over solids is vital to
spacecraft fire safety. The spacecraft environment may vary in oxygen concentration and is
characterised by convective flows in the range of 0 - 50 cm/s. The past researches have shown that
these conditions are more conducive for flames to spread over solids compared to normal gravity.
In microgravity, radiation becomes the dominant heat transfer mode and longer residence time
favours soot production. Further microgravity experiments have shown that as oxygen
concentration is reduced to near limit conditions, the flames break into smaller flamelets and these
are thought to extend the range of material flammability. The oxidation of char formed during
pyrolysis in the near-limit conditions may be responsible for the size and shape of the flamelets
formed and possibly influence material flammability. In order to answer the above questions, in the
present work an in-house 3D numerical will be modified by incorporating models for char and soot
formation and their oxidation to simulate near limit formation of flamelets and their extinction in
microgravity environments. The role of solid material properties in this regard will also be explored.