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Directional Solidification of Mercury Cadmium Telluride in MicrogravityMercury cadmium telluride (MCT) has been directionally solidified for ten days in the Advanced Automated Directional Solidification Furnace (AADSF) on the second United States Microgravity Payload Mission (USMP-2). A second growth experiment is planned for the USMP-4 mission in November 1997. Results from USMP-2 demonstrated significant changes between microgravity and ground-based experiments, particularly in the compositional homogeneity. Changes were also observed during the microgravity mission which were dependent on the attitude of the space shuttle and the relative magnitudes of axial and transverse residual accelerations with respect to the growth axis of the crystal. Issues of shuttle operation, especially those concerned with safety and navigation, and the science needs of other payloads dictated the need for changes in attitude. One consequence for solidification of MCT in the USMP4 mission is the desire for a shorter growth time to complete the experiment without subjecting the sample to shuttle maneuvers. By using a seeded technique and a pre-processed boule of MCT with an established diffusion layer quenched into the solid, equilibrium steady state growth can be established within 24 hours, rather than the three days needed in USMP-2. The growth of MCT in AADSF during the USMP-4 mission has been planned to take less than 72 hours with 48 hours of actual growth time. A review of the USMP-2 results will be presented, and the rationale for the USMP-4 explained. Pre-mission ground based tests for the USN4P-4 mission will be presented, as will any available preliminary flight results from the mission.
Document ID
19990097528
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Lechoczhy, Sandor L.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Gillies, Donald C.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Szofran, Frank R.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Watring, Dale A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Subject Category
Materials Processing
Meeting Information
Meeting: Experimental Methods for Microgravity Materials Science
Location: San Antonio, TX
Country: United States
Start Date: February 16, 1998
End Date: February 19, 1998
Sponsors: Metallurgical Society
Distribution Limits
Public
Copyright
Other

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