Front view camera Side view camera Fuel holder O 2 port N 2 port Vacuum pump port Manometer port Apparatus for normal-gravity experiments CCD camera Air Honeycomb Fan PMMA 30mm x 10mm x 15,50,125 m Fuel holder Igniter (Ni-Cr wire) Apparatus for micro-gravity experiments conducted with the 4.5sec trop-tower (100meter-drop) of MGLAB in Japan. Igniter (Ni-Cr wire) Fuel holder Vacuum O2O2 CCD camera Air Igniter (Ni-Cr wire) VfVf VfVf Fuel holder VgVg V g ~300mm/sec PMMA 30mm x 10mm x 15,50,125 m V r = V f + V g Spread rate in micro-gravity with varying opposed-flow velocity, oxygen level and fuel thickness Spread rate in quiescent normal- and micro-gravity O2 level: 21% Pressure: 1atm Spread rate in G Spread rate in NG Ratiative effect due to small V f. Thermal-regime spread due to large V f 0.00sec (Ignition) 0.918sec1.836sec2.584sec 2.720sec2.754sec2.822sec3.400sec The unsteady spread observed when the oxygen level is 50% and the fuel thickness is 125 m Radiative loss flame Mass diffusion layer Temperature diffusion layer Unsteady flame spread in micro-gravity (quiescent condition) Scale of the temperature diffusion layer shrinks.