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7 July 1997 Conceptual design for a rotational mechanism aboard the space shuttle for long-duration processing of semiconducting alloys under optimal residual acceleration conditions
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Abstract
Successful ground based research of certain classes of semiconducting alloys is oftentimes difficult to accomplish due to the ever present effects of gravity acting on the sample during processing. Buoyancy-driven convection in the melt can prevent the formation of a stable boundary layer and hence diffusion-controlled growth conditions. In theory, if such experiments are conducted in the microgravity environment of space, buoyancy-driven convection effects due to gravity are essentially eliminated. Even under weightless conditions, however, some classes of semiconducting alloys remain sensitive to the direction of the residual acceleration vector. The residual acceleration environment is comprised of drag, gravity-gradient, and rotational acceleration contributions that are always present on orbit. These contributors are a function of shuttle attitude, altitude, atmospheric conditions, and the distance away from the shuttle center of gravity. It is possible, through orbital dynamics studies, to provide a shuttle attitude that aligns the residual acceleration vector in an ideal direction relative to the crystal growth axis. Due to shuttle hardware limitations it is often not possible to maintain these desired shuttle attitudes over extended periods of time while critical sample processing is being conducted. The development of a rotating mechanism, integrated with a crystal growth furnace, will allow experimenters the opportunity to process their samples under ideal residual acceleration conditions with no deviations from the desired shuttle attitude, while meeting all the on-orbit shuttle hardware requirements. Such a mechanism can be incorporated into existing hardware and can be flown on multiple shuttle flights to satisfy various science team sample processing requirements, independent of the varying on-orbit conditions that exist from flight to flight.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Brian P. Matisak, Donald C. Gillies, and Richard W. Howard "Conceptual design for a rotational mechanism aboard the space shuttle for long-duration processing of semiconducting alloys under optimal residual acceleration conditions", Proc. SPIE 3123, Materials Research in Low Gravity, (7 July 1997); https://doi.org/10.1117/12.277726
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