Role of a space station in materials processing
Previous work in materials processing (MP) in space is reviewed, and the role of a space station for future MP programs is examined. Historical MP experiments have been carried out in drop tubes, on aircraft in parabolic trajectories, on SPAR rocket flights, and on the Skylab and Soyuz-Apollo missions. The trials demonstrated gravity-driven convection is eliminated in molten materials, giving rise to expectations that crystals, alloys, and chemical or biological materials can be handled without convective disturbances that gravity causes. Particles of a significantly higher density can remain in suspension in an alloy in the molten state until resolidification. Containerless processing can be implemented at very high temperatures using acoustic, electrostatic, and EM levitation techniques. Convective influences on earth can be identified by their absence in space. The construction of a space station will permit longer-term and larger mass and volume experiments, as well as a closer step to actual commercial enterprises in space.