STS-87 Mission Science Report # 5s
Monday, November 24, 1997, 7:00 a.m. CST
Spacelab crew members and science teams at Marshall Space Flight Center in Huntsville, Ala., worked steadily through the night to complete as much science as possible in the remaining hours of the mission. Due to a malfunction in the Space Shuttle’s number two fuel cell, Columbia is now scheduled for landing Tuesday afternoon.
The abbreviated mission came as a disappointment to participating scientists. The atmosphere, however, was also marked by bright spots, such as the excitement of one science team which recorded a “first” in combustion research. Payload Commander Dr. Janice Voss completed several runs of the Droplet Combustion Experiment last night. “Six burns were successful and for the first time, we’re burning free droplets,” said Principal Investigator Dr. Forman Williams of the University of California at San Diego.
The experiment is collecting information on burning rates of flames, flame structures and conditions under which flames are extinguished. “We can’t get this kind of information from ground-based experiments,” said Williams. “We have burned at two different atmospheres of oxygen concentration and calculated the burning times of free fuel droplets at each.”
Combustion of fuel droplets is an important element in heating furnaces for materials processing, heating homes and businesses, and producing energy in gas turbines and gasoline-powered engines. Findings from this investigation are providing 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.
The Coarsening in Solid-Liquid Mixtures experiment continued to run in the Middeck Glovebox facility. This investigation, led by Dr. Peter Voorhees of Northwestern University in Evanston, Ill., is studying coarsening in metal mixtures at very high temperatures. During coarsening, small particles shrink by losing atoms to larger particles, resulting in a lack of uniform particle distribution. This weakens the material and shortens its life-span.
“Because of our small size and power usage we’ve been able to continue experiment runs, completing four runs with good success,” said John Caruso, project manager for the experiment, with NASA’s Lewis Research Center. “From the engineering data we’ve received, we expect to get satisfactory science. We expect the samples will show uniform particle distribution.”
Findings from this research may lead to improved manufacturing processes and stronger, longer-lasting materials.
Early Sunday evening, Payload Specialist Dr. Roger Crouch began a study of the Structure of Flame Balls at Low Lewis-number, called SOFBALL, in the Combustion Module. The study is designed to determine under what conditions a stable flame ball can exist and if heat loss is responsible in some way for the stabilization of the flame ball during burning.
“The two completed runs were successful beyond my wildest dreams,” said Principal Investigator Dr. Paul Ronney of the University of Southern California in Los Angeles. During the first experiment, a mixture of hydrogen, oxygen and carbon-dioxide burned in the facility for the entire 500-second limit. This result is significant because, “these are the weakest flames ever burned -- lowest temperature, weakest, most diluted mixtures,” explained Ronney. “These mixtures will not burn in Earth’s gravity.”
“We have known that burning weaker mixtures increases efficiency,” said Ronney, “but not much is known about the burning limits of these mixtures.” Findings from this experiment will also provide researchers with a better understanding of the combustion process and will help to improve theoretical models. “Combustion models give different results for these types of flames,” said Ronney. “This is an acid test to show which, if any, current combustion modules should be used.”
The Experiment Control Systems Computer, which relays ground-commands to the experiment facilities, malfunctioned. The Spacelab crew performed a procedure to disconnect the computer from the master timing unit, allowing the computer and experiments to go to internal timing sources.
In the electromagnetic containerless processing facility, called TEMPUS, two experiment runs ended early when the undercooled, levitated samples came in contact with the wall. Undercooling refers to a liquid being cooled to a temperature below its normal freezing point yet remaining in a liquid state -- like cooling a glass of distilled water on Earth. However, if the glass is tapped or disturbed, ice begins to form quickly -- just as the samples began to solidify when they hit the wall. Another study of undercooled materials was initiated in the facility. This experiment, which measures the specific heat of undercooled metallic melts, is examining how metallic glass forms in zirconium-based alloys.
Before ending his shift early this morning, Crouch began another run of the Liquid Phase Sintering experiment in the Large Isothermal Furnace. This experiment is investigating how liquid metals form a mixture without reaching the melting point of the formed metallic alloy. Information gathered will provide researchers with a better understanding of liquid phase sintering in low-gravity and comparisons of findings to theoretical predictions, should improve theoretical models. The principal investigator for the study is Dr. Randall German of Pennsylvania State University in University Park, Pa.
Dr. Donald Thomas and Dr. Gregory Linteris assumed science operations aboard the Shuttle early this morning. Thomas completed another run of the Liquid Phase Sintering experiment in the Large Isothermal Furnace before beginning to deactivate protein crystal growth experiments.
After completion of another run of the Droplet Combustion Experiment, Linteris began reconfiguring the Droplet Combustion Apparatus for return to Earth.
Ahead, crew members will continue to deactivate experiment facilities in preparation for the Shuttle’s journey home.
The next scheduled Public Affairs Status report will be issued at approximately 6 p.m., April 7.
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