Bubble migration inside a liquid drop in a space laboratory

Commercial production of glasses for advanced applications often requires processing techniques substantially different from those in common use. In particular, containerless processing is desirable where melt temperatures are sufficiently high that the container wall reacts chemically with the melt and/or promotes crystallization. An ideal environment for containerless processing is provided by the NASA Space Shuttle program because in orbit, near free fall conditions prevail and little levitation is necessary. In such an environment, however, there are serious problems associated with convective mixing and buoyant fining (bubble removal) of glass melts. Alternate techniques for the promotion of mixing and for managing bubbles in space have been proposed by Subramanian and Cole and include thermocapillarity, rotation, oscillation, etc. This paper will describe these experiments and discuss two of a number of ongoing ground-based projects in support of the flight experiments.