STS-87 Mission Science Report # 2s
Friday, Nov. 21, 1997, 7:00 a.m. CST
Aboard Space Shuttle Columbia Thursday, furnaces were fired up for several research studies, and other experiments were supercooled as scientific research in the microgravity of space proceeded in earnest.
With most all of Columbia’s science payload — known as the U.S. Microgravity Payload-4 — activated, and its experiments under way, important findings are already exciting researchers. “From preliminary results,” said Assistant Mission Manager Jimmie Johnson, “it looks like we’re going to have a great science mission. We’ve gotten a good start on science for this 16-day mission, and all of our systems are performing well.” The science goals of the mission include a study of materials used by industry, research into the unwanted extinction of flames, and the continued miniaturization of computer chips.
Early Thursday afternoon, Mission Specialists Dr. Kalpana Chawla and Dr. Takao Doi performed the first materials science experiment inside a thermal chamber in the Microgravity Glovebox. Researchers are looking at how to create a uniform mixture of the liquids that form certain metal alloys, such as those used in simple bearings or complex superconductors. These alloys are made up of two liquids that do not mix well.
When such metals are processed on Earth, gravity causes the liquids to separate — much the same way as water and oil. This separation causes weaknesses in metal structures. Previous tests of these alloys conducted in the low gravity of space revealed unexpected separation of their components into layers. Scientists expect that one possible cause of the separation is droplet wetting — or coating — along container walls. The experiment initiated Thursday is designed to study ways to control this wetting behavior. Developing a method to eliminate the separation will help create better materials, leading to many benefits on Earth.
Dr. Barry Andrews of the University of Alabama at Birmingham, who leads the experiment, said late Thursday, “The first two experiment samples were processed with fascinating results.” Andrews said those initial samples consisted of compositions where preferential wetting of the gasket material had not been previously observed during processing on Earth. The flight samples indicated a noticeable tendency toward wetting — even for compositions with the lowest content of a colorless crystalline material known as succinonitrile. “This result,” said Andrews, “was completely unexpected and will provide substantial information on the importance of wetting tendencies.”
Scientists on Earth Thursday pored over video images, transmitted from Columbia, clearly showing the continuing growth of dendritic crystals — structures which look much like miniature pine trees. In this experiment, materials are melted and resolidified to observe the growth of dendrites. Metal alloys form dendrites when they crystallize, ultimately creating the strong materials used in production of automobiles and jet engines. Results of this study may improve manufacturing of steel, aluminum and super alloys.
Because Earth’s gravity distorts dendrites as they grow, dendrite crystals produced in the low-gravity of space reveal new information about dendrite formation. The experiment’s principal investigator, Dr. Martin Glicksman of the Rensselaer Polytechnic Institute at Troy, N.Y., said late Thursday that information already gathered from the experiment “is providing extremely valuable insight into microgravity solidification behavior of pivalic acid — our primary test substance.” Glicksman was especially impressed with the high quality of the video downlinked from Columbia Thursday. “It will doubtless lead to new scientific findings about dendrite growth dynamics,” he added.
A furnace onboard Columbia was heated up Thursday to 750 degrees Celsius — or 1,382 degrees Fahrenheit — in a joint experiment between NASA and the French Space Agency studying crystal growth in space. Samples processed in the furnace, known as MEPHISTO, will help researchers understand how gravity-driven convection affects production of metals -- including alloys -- and electronic materials. Precise temperature control allows the crystals to grow gradually —without the effects of Earth’s gravity. The result is large, nearly perfect crystals. For electronic applications, better crystals reduce power needs and increase data handling rates. In metals, more perfect crystals result in improved strength and durability. Three different sample cartridges containing the metal bismuth, with small additions of tin, will be processed in the furnace using directional solidification — a common method for growing semiconductors and metal alloys. The temperature, speed of growth, and the shape of the crystals solidifying within each sample are to be measured in three different ways to identify the internal structure of the crystal.
Project scientist and co-investigator of the study, Henry C. de Groh III of NASA’s Lewis Research Center in Cleveland, Ohio, said early Friday morning, “We’re completing our first solidification and melt cycle now. Everything is going great. This is one data point. We solidify and melt at one velocity, and then we will do several other velocities. Ultimately, we will produce new results on solidification.”
During the next 24 hours, the Spartan solar physics spacecraft is to be deployed from Columbia. Deployment had been scheduled on Thursday, but was delayed due to a problem with SOHO — the Solar and Heliospheric Observatory. That delay resulted in a number of science experiments, originally scheduled Friday, to be conducted Thursday. Also ahead: The Automated Directional Solidification Furnace will be reactivated for an upcoming crystal growth experiment, and another metal alloy sample will be processed in the MEPHISTO furnace.
The next scheduled Public Affairs status report will be issued at approximately 7 a.m., Saturday, Nov. 22. 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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