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Thursday, July 3, 1997, 7 p.m. CDT
STS-94 Mission Science Report # 5s

Aboard Space Shuttle Columbia this morning Mission Specialist Dr. Donald Thomas transferred the plant growth experiment from the Shuttle’s middeck to the EXPRESS Rack, a facility designed for quick and easy installation of hardware and experiments on Space Station. The plant growth experiment is one of two Microgravity Science Laboratory studies that will check the design, development and adaptation of the EXPRESS Rack.

Called the ASTRO/Plant Generic Bioprocessing Apparatus, the plant growth experiment is studying the effect of space on certain types of plants. The investigation examines the production of lignin, essential for the formation and joining of woody cell walls in plants; the production of secondary metabolites, essential for generating energy needed to sustain vital life processes; and changes which occur in the sugars and starches of vegetable plants.

Researchers are interested in determining if these plant processes are interrelated and how they might be manipulated to improve plant growth and production on Earth. Findings may also verify evidence that plants grown in microgravity require less metabolic energy to produce lignin, permitting greater production of secondary metabolites, a source of many medicinal drugs. Secondary metabolites may also be used to attract, repel or poison insects.

Plants being studied aboard Space Shuttle Columbia, include Artemisia annua, a species of sage native to Southeast Asia and a source of the antimalarial drug artemisinin; Catharanthus roseus, which produces vinca alkaloids, used in chemotherapy treatment of cancer; Pinus taeda, or loblolly pine, used widely in the paper and lumber industries; and Spinacia oleracea, a variety of spinach.

Payload Specialist Dr. Gregory Linteris performed a shear cell rotation of the sample processing in the Large Isothermal Furnace. This procedure is part of a study which tests a specially designed shear cell cartridge to determine the diffusion coefficient -- a fundamental quantity which describes the diffusion process -- of tin.

The shear cell method involves two column samples, one pure sample and one sample with an additive. The columns are melted, then rotated into contact with each other for a specific period of time. The resulting single column is sheared into segments and cooled for post-flight analysis. “Outward signs of a good experiment are duration and steadiness of temperature -- the environment -- and the completeness of each rotation,” said Richard Dewitt, senior project engineer with NASA’s Lewis Research Center. “Today’s experiment was right on the money.”

These investigations are providing researchers with a better understanding of the diffusion process and may lead to improved techniques for processing metallic alloys on Earth and in turn better products.

Linteris completed a second successful run today of a propane-fueled soot study to investigate the properties of soot. “We are burning fuels at different atmospheres because soot is very sensitive to pressure. The higher the pressure the more soot produced,” said Dr. Gerard Faeth of the University of Michigan in Ann Arbor.

Later in the day another test run was completed using Ethylene fuel. “Different fuel types also make a big difference,” explained Faeth. “Natural gas, for instance, tends to make little soot. And it is widely used in the U.S., so it is of interest to us. Propane produces more soot, and Ethylene, used in diesel engines, produces even more.”

Information from this study may lead to a better understanding of how to contain unwanted fires and limit the number of fatalities from carbon monoxide emissions.

Payload Commander Dr. Janice Voss and Payload Specialist Dr. Roger Crouch assumed science operations just after noon today.

Voss began a series of small droplet runs this afternoon to study a burning fuel droplet of heptane, part of the Droplet Combustion Experiment. The investigation is collecting information on burning rates of flames, flame structures and conditions under which flames are extinguished. Findings from this study will provide researchers with a better understanding of the combustion process and may lead to cleaner and safer ways to burn fossil fuels as well as more efficient methods of generating heat and power on Earth.

Crouch initiated a run of the Liquid Phase Sintering experiment in the Large Isothermal Furnace. During the experiment samples of tungsten, nickel and iron and tungsten, nickel and copper are heated to 1,500 degrees Celsius. When heated, nickel, iron and copper will melt to create solid-liquid mixtures. “Sintering is thermal heating that causes particles to bond together,” said Dr. Randall German with Pennsylvania State University. “On Earth, sintering distorts the material. We are trying to learn the rules of why things distort on Earth. And we are.”

Late this afternoon, Crouch conducted a fluid physics experiment in Middeck Glovebox facility. The Internal Flows in Free Drop experiment examines techniques for controlling the position and motion of liquids in low-gravity. Results may find application in improving many important processes used by chemical manufacturing industries on Earth, including the petroleum technology, cosmetics and food sciences industries. The study is lead by Dr. S.S. Sadhal of the University of Southern California in Los Angeles.

The computer system aboard the Shuttle which sends commands to experiment facilities had to be rebooted twice this afternoon after it locked up. The crew was able to reboot the system with no impact to science.

The TEMPUS team believes it has now resolved a problem experienced earlier this morning involving a temperature controller used to melt material samples. The team is continuing to troubleshoot a problem with one of the two video cameras used to record data from the experiment. As a result of trouble shooting efforts, one of the planned experiment runs has been delayed.

Ahead, Crouch will complete another test of the soot experiment in the Combustion Module. Voss will continue with the Droplet Combustion Experiment. Voss will exchange the sample in the Large Isothermal Furnace and conduct another run of the Liquid Phase Sintering experiment.

The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 4.


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