STS-87 Mission Science Report # 7s
Wednesday, November 25, 1997, 7:00 a.m.CST
Research results that will affect the future of transportation and electronics industries continue to pour into the Spacelab Mission Operations Control Center at the Marshall Space Flight Center in Huntsville, Ala., as Space Shuttle Columbia’s crew focuses on the Fourth United States Microgravity Payload experiments.
Experiments continued in the glovebox overnight. Mission Specialist Dr. Kalpana Chawla assisted by Mission Commander Kevin R. Kregel worked through this morning on the materials mixing experiment called “Particle Engulfment and Pushing by a Solid/Liquid Interface.”
As liquid metals solidify, a plane of atoms form a line known as the solidification interface. As this line moves, particles are either pushed ahead of, or engulfed by the emerging solid mass. Researchers want to know why some particles are engulfed and others pushed. By understanding this process, they hope to design stronger and lighter composite materials for use in the auto and aerospace industry. The knowledge could also provide an understanding of how and why pot holes form in roads and highways and how to prevent them.
The glovebox briefly overheated and shut down twice last night, but in a surprise twist the result proved beneficial rather than detrimental to the experiment.
Dr. Doru Stefanescu of the University of Alabama in Tuscaloosa said his team had been having difficulty observing the particles and whether they were being pushed or engulfed as the sample solidified. And when the glovebox shutdown, the sample partially solidified, obscuring the position of the solidification line. However, during restart, the sample was remelted, making it translucent and allowing Stefanescu’s team to record the positions of the particles and determine whether they were being pushed or engulfed. “The shutdowns have taught us to use a different technique for our next experiment runs,” said Stefanescu. “Sometimes things that happen like that are good. “This is very promising. We’re looking forward to tomorrow night’s experiment runs.”
In another experiment, this one out in the cargo bay, the growth of tiny pine-tree shaped dendrites is leading researchers to a better understanding of new ways to manufacture steel, aluminum and superalloys for use in transportation and construction industries. Researchers at Marshall Center and the remote “telescience” location at Rensselaer Polytechnic Institute in Troy, N.Y., have been conducting the Isothermal Dendritic Growth Experiment almost non-stop since Columbia reached orbit.
Using video images of pivalic acid, the investigators watch as the melted material solidifies before the camera lens and forms the dendrite crystals. The video downlink is providing valuable data on crystal initialization and growth dynamics. The team is analyzing these early results to solve the puzzle of metallic strength and structure.
Overnight, the MEPHISTO team finished two more melting cycles of the bismuth and tin sample in the furnace experiment. “The hardware is really working great,” said William Foster, project manager from NASA Lewis Research Center in Cleveland, Ohio. “We’re seeing new data and adjusting our experiment to maximize our results.”
Starting later today, plans call for Columbia to be oriented to best support the Advanced Automated Directional Solidification Furnace investigation. The 70 hour long melting and solidification experiment is designed to produce a single, unique electrical crystal with exceptional compositional uniformity. From this, researchers hope to improve metallic crystal structure and to enhance their performance in electronics, computers and infrared detectors.
“The idea is to get the most uniform composition,” said experiment co-investigator Dr. Donald C. Gillies of the Marshall Center. “We can only get this uniformity in microgravity. We are taking two metals, opposite from each other on the spectrum -- one metallic and one semiconductor -- and mixing them together.”
Gillies’ furnace experiment entitled “Growth of Solid Solution Single Crystal” will melt and mix a sample of the mercury, cadmium and telluride alloy. Throughout the processing, the furnace will maintain a temperature of over 1,800 degrees Fahrenheit.
Generally used as infrared detectors, the sample materials are currently used by devices that see in the dark or see through clouds. Though Gillies’ sample is a tough one to grow, researchers believe that the resulting crystal could detect different infrared energy levels from anything ever produced before.
“We’re having a great mission,” said USMP-4 Mission Manager Sherwood Anderson, “we’re getting to the heart of our experiments now.” Anderson said the possibility of a Spartan satellite redeployment is not expected to impact the time allotted for the microgravity experiments.
Looking ahead to the next 24 hours, Columbia’s crew members will resume metal mixing and combustion experiments in the middeck glovebox. Science teams will continue the metal mixing experiments in the MEPHISTO furnace and begin inserting the single crystal sample into the Advanced Automated Directional Solidification Furnace.
The next scheduled Public Affairs status report will be issued at approximately 7 a.m., Thursday, Nov. 27. 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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