Dendritic growth measurements in microgravity

Abstract

The Isothermal Dendritic Growth Experiment (IDGE) is an orbital space flight experiment, lauched by NASA, in March, 1994, as part of the United States Microgravity Payload (USMP-2). The IDGE provided accurately measured dendritic growth rates, tip radii of curvature, and morphological observations of ultra-pure succinontrile in the supercoolings range between 0.05–2.0 K. Data were received in the form of pairs of digitized binary images telemetered to the ground from orbit in near-real-time, and as 35mm photographic film. The data taken above ca. 0.4 K supercooling provide the first comprehensive assessment of diffusion-limited dendritic growth, and those taken below this value yield new insights into the influence of convection. The IDGE also demonstrated that prior terrestrial dendritic growth data were generally corrupted by melt convection, making their comparison with diffusion-limited theories questionable. A key element in the design and operation of this experiment, which was in development for over ten years at a cost of approximately $12 million U.S., was its reliance on telescience for accomplishing in situ near-real-time monitoring and control of the experiment.