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Friday, November 28, 1997 - 7:00 a.m. CST
11.28.97
 
STATUS REPORT : STS-87-09s
 
 
STS-87 Mission Science Report # 09s
 
 

As the Thanksgiving holiday was wrapping up, cutting-edge research to improve high-tech electronics, satellite imaging and computers continued aboard Columbia. Thursday night, the Space Shuttle crew also received a phone call from President Bill Clinton thanking them for their dedication and hard work over the holiday.

For almost 36 hours, the Shuttle has been maintaining an orientation best suited to support a sensitive investigation studying an alloy that could greatly improve infrared detectors. Early Friday, a sample of the mercury, cadmium and telluride alloy began solidifying to produce a single, unique electrical crystal in the Advanced Automated Directional Solidification Furnace.

"One of our objectives on this flight is to get benchmarks -- near-perfect materials that can be used to compare with and judge materials made on Earth,” said the experiment’s lead investigator, Dr. Sandor Lehoczky of the Marshall Space Flight Center in Huntsville, Ala.

In previous missions, "We demonstrated that under favorable Shuttle orientations, one can grow crystals with improved composition and structural perfection as compared to those grown on the ground under otherwise identical conditions,” said Lehoczky.

"For this mission, we have tried to select a more optimum orientation to further demonstrate the correlation between residual acceleration, which defines ‘up,’ and compositional uniformity."

“We’re working on the materials for the future,” said the experiment’s co-investigator Dr. Dale Watring of Marshall. “The study of the ‘mer-cad-telluride’ alloy is in its infancy. We’ve only begun to scratch the surface of what could be possible.”

Late Thursday evening, Mission Specialist Dr. Kalpana Chawla and Commander Kevin Kregel conducted an experiment in the glovebox facility to investigate certain metal alloys which do not mix well.

Immiscible metallic alloys act like oil and water when combined in a liquid state on Earth. Scientists believe that if uniformly dispersed, these materials could have desirable properties for use in infrared detectors, superconductors and magnets.

"In our first science mission, we thought that if we took these metals into space, heated them to a high temperature -- so they mixed -- and then cooled them, we would get a uniform dispersion of the materials. Instead, the samples often came back with all of one material clumped in the middle, and the other surrounding it, providing us with a new mystery,” said the lead investigator, Dr. Barry Andrews of the University of Alabama in Birmingham.

To study this unexpected separation process called wetting, Andrews’ team chose succinonitrile, an industrial chemical used in making nylon, and glycerol, a chemical used in the cosmetics industry. “They separate like oil and water, and both are transparent, so segregation can be readily seen. They also behave quite similarly to metallic systems," said Andrews.

Chawla and Kregel completed several runs of the experiment. For each run, they placed a sample cell (composed of the two materials between two glass slides held separated by a Teflon gasket ) in a small furnace contained in the Middeck Glovebox. The cells were heated to 194 degrees F to allow mixing and then placed on a cooling rack in the glovebox to cool to 86 degrees F.

As the sample cooled, the astronauts watched through a microscope and sent video to the ground. “We are very pleased with our science data so far. We’ve learned that the extent of the materials’ separation depends on the container and different temperature phases,” said Andrews.

In the MEPHISTO furnace -- a cooperative study by NASA, France and Australia to grow crystals in space -- researchers continued to process sample cartridges of the metal bismuth, with small additions of tin, using directional solidification , a common method used to grow semiconductors and metal alloys. As the samples solidified during the test runs, the scientists looked at the temperature, speed of growth, and shape of the crystals.

In another materials experiment, the science team studying dendrites -- microscopic tree-like structures that form in metals as they solidify -- collected data from their final scheduled dendritic growth cycle Thursday.

Virtually all alloys used in industrial processes solidify from a molten state by dendritic growth. By enhancing the basic understanding of dendritic solidification, industrial production techniques on Earth may be improved.

“Although our primary science is complete, we hope that there will be opportunities during the remainder of the flight to get additional growth cycles at a variety of temperatures,” said the experiment’s lead investigator, Dr. Martin Glicksman of the Rensselaer Polytechnic Institute in Troy, N.Y.,

During the 24 hours ahead, crew members will perform the first test runs of a combustion experiment which studies how various air flow currents can influence the stability of flames, and the mercury, cadmium and telluride alloy sample will continue to solidify in the Advanced Automated Directional Solidification Furnace. In the Confined Helium Experiment, researchers will continue to take ultra-precise measurements in cooled, liquid, “superfluid” helium — which conducts heat 1,000 times more efficiently than any other material.

The next scheduled Public Affairs status report will be issued at approximately 7 a.m., Saturday, Nov. 29. For more information call the Spacelab Newscenter at Marshall Space Flight Center at (205) 544-0034 or visit the web sites: For USMP-4 payload and science information: http://liftoff.msfc.nasa.gov/shuttle/usmp4/ and http://science.msfc.nasa.gov/usmp4/usmp4.htm For STS-87 information: http://www.shuttle.nasa.gov

 

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