STS-87 Mission Science Report # 08s
Thursday, November 27,1997, 7:00 a.m. CST
As many in America began celebrating the Thanksgiving holiday, researchers aboard the Space Shuttle Columbia and in the Spacelab Mission Operations Control Center at the Marshall Space Flight Center in Huntsville, Ala., continued to reap a harvest of scientific knowledge from the fourth flight of the United States Microgravity Payload.
Mission Specialist Dr. Kalpana Chawla and Mission Specialist Dr. Takao Doi worked well into the morning on material mixing experiments in the glovebox.
The first, called “Particle Engulfment and Pushing by a Solid/Liquid Interface,” provided investigators with some unexpected observations. They watched as floating loose particles bunched together to form larger particle clumps -- as commonly observed during ground experiments. But for the first time, they observed the large particle clumps being pushed in front of the solidifying mass, rather than being engulfed by it. Investigators think the understanding of this complex mixing process is the key to plastics, ceramics and alloys of the future.
The experiment is a studying how liquid metals solidify and why some particles are engulfed and others pushed along -- in the liquid -- in front of the solidifying mass. Investigators hope to understand this process to design stronger and lighter composite materials.
After completing several of the particle experiment runs, the glovebox was reconfigured for the Wetting Characteristics of Immiscibles experiment. Dr. Barry Andrews of the University of Alabama in Birmingham, Ala., leads the investigation to discover how to create a uniform mixture of certain metal alloys which do not normally mix well.
Results from this experiment may lead to improved materials on Earth ranging from simple ball bearings to complex semiconductors. Andrews said that the low-gravity processing conditions are necessary to see the results of the experiment. Though still early, he described last night’s results as, “Fantastic, exactly what we wanted to see.”
The glovebox -- a contained workplace for hazardous material -- experienced overheating problems that somewhat slowed the pace of the research last night.
In the early hours of the holiday morning, investigators studying the Confined Helium Experiment, finished recording over 14 hours of very sensitive temperature measurements of liquid helium. Co-investigator Dr. Talso Chui, from the Jet Propulsion Laboratory in Pasadena, Calif., said the experiment’s thermometers performed so well that they did not drift by even one nano-degree -- or a billionth of a degree.
“We have to take many measurements to prove our thermometers are stable and we have done it,” Chui said. “It has to be this stable or we cannot use the information.”
Results from the experiment are expected to explore the limits of how microprocessors can be reduced in size and how electrical performance is affected. Better understanding of miniaturization may lead researchers to the development of even smaller electronic devices with better capabilities.
For the first time -- by using the low-gravity environment of space -- the MEPHISTO team has been able to observe two separate processes of solidification. Results have shown that solidification occurs a little bit below the melting point of a material and depends upon -- the material composition -- and how atoms from the liquid material attach themselves to the forming solid.
As the furnace experiment continued to perform melting cycles of the bismuth and tin sample throughout the morning, researchers strive for understanding that can improve the quality of superconductors and electronic structures. The experiment is a joint effort of the United States, France and Australia.
“We are very happy with the performance of the MEPHISTO hardware,” said Dr. Gerard Cambon of the French Space Agency. “The French team has participated in this experiment for the last 18 months and we have worked in a cooperative effort to enhance the science gains,” Cambon said.
Since last night, Columbia has been drifting in an orientation best suited to support a time consuming and sensitive Advanced Automated Directional Solidification Furnace investigation. It will take one day to melt the mercury, cadmium and telluride alloy sample and two days to solidify it in order to produce a single, unique electrical crystal with exceptional compositional uniformity. From this, researchers hope to understand metallic crystal structures and enhance their performance in electronics, computers and infrared detectors.
“The science teams are getting terrific science data from space that will improve life on Earth in areas that extend from computers to the medicine,” said NASA’s USMP-4 Mission Program Scientist Dr. Michael Wargo.
Looking ahead to the next 24 hours, Columbia’s crew members will resume metal mixing investigations in the glovebox. Science teams will continue liquid helium measurements as the Advanced Automated Directional Solidification Furnace begins mixing the infrared crystal sample.
The next scheduled Public Affairs status report will be issued at approximately 7 a.m., Friday, Nov. 28. 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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