Dendritic crystal growth in microgravity

Microgravity is the unique environment created during space flight. in free fall along a low-Earth orbit (LEO). Although the precise acceleration conditions achieved on a space craft during free fall in LEO depend upon a number of factors.. some of which will be dis- cussed in these notes, one generally call achieve a quasi-steady acceleration of ca. 10(-6)g0: where go denotes the average acceleration of gravity experienced on the surface of the Earth at sea level, approximate to 9.8m.s(-2). In addition, if one attempts crystal growth in microgravity, a spectrum of "g-jitter" is unavoidably encountered, which is random, oscillatory. accelerations and vibrations. G-jitter, which call influence some growth processes. arises from the presence of rotating equipment, such as pumps and fans, and from the movement of astronauts who might be oil board. The main focus of these notes will be to review the scientific accomplishments of three space flight, crystal growth experiments carried out on board the space orbiter/shuttle Columbia in 1994; 1996: and 1997. Each experimental hardware system was a primary component of the United States Microgravity Payload Missions (USMP 2 3, and 4). These experiments addressed fundamental questions concerning dendritic crystal growth, and were named by the National Aeronautics and Space Administration (NASA) as the Isothermal Dendritic Growth Experiment (IDGE). IDGE-1 and IDGE-2 were experimental hardware systems dedicated to testing scientifically the relevant transport and interfacial physics theories describing the steady-state dendritic crystal growth of pure succinonitrile (SCN), which is a body-centered cubic (BCC) crystal with extremely low anisotropy of the crystal-melt, interfacial energy. IDGE-3 was a follow-on experiment that used an advanced hardware system to test similarly the steady-state crystal growth of pure pivalic acid (PVA), which is a face-centered cubic (FCC) crystal with a relatively large anisotropy of the crystal-melt, inierfacial energy. IDGE-3 also accommodated on-board video recording and down-linked telemetry of dendritic growth and mushy-zone melting processes, some of which will be presented during the lecture sequence. The results from these microgravity space-flight, experiments: each conducted during a typical 2-week orbital mission, built a solid experimental foundation that tested prevailing transport theories of dendritic crystal growth. In addition. space experiments confirmed the broad validity of so-called dendritic "scaling laws," which will be developed fully in these notes. Finally, the three space flight experiments created at, archive that is proving useful for "benchmark" testing of modern dynamical theoriess of dendritic growth, including advanced computer simulation techniques based on methods such as phase field and level sets.