DENDRITIC GROWTH VELOCITIES IN MICROGRAVITY

We measured dendritic tip velocities in pure succinonitrile (SCN) in microgravity, using a sequence of telemetered binary images sent to Earth from the space shuttle Columbia (STS-62). Growth velocities were measured as a function of the supercooling over the range 0.05-1.5 K. Microgravity observations show that buoyancy-induced convection alters the growth kinetics of SCN dendrites at supercoolings as high as 1.3 K. Also, the dendrite velocity data measured under microgravity agree well with the Ivantsov paraboloidal diffusion solution when coupled to a scaling constant of sigma* = 0.0157.