STS-94 Mission Science Report # 11s
Tuesday, July 8, 1997, 7 a.m. CDT
As the Microgravity Science Laboratory mission approaches the half-way mark of its planned 16-day flight, researchers are reporting overall good results so far, and one of the combustion science research teams, which completed its experiment last night, says the information it gathered on this mission is even better than hoped for.
Payload Commander Dr. Janice Voss performed the last run of the Laminar Soot Processes experiment in the Combustion Module last night, and according to lead scientist Dr. Gerard Faeth of the University of Michigan at Ann Arbor, “it was gorgeous; the best of them all.” Between both missions, the one in April and this one, 17 tests were completed, three more than originally scheduled. “Every one worked and yielded good data,” said Faeth. “That was beyond my wildest dreams.”
Researchers learned that achieving non-buoyant, or steady, flames is a lot tougher than thought and so was predicting some of the flame burning characteristics. “After the first few runs we got some starting points, and it was easy to predict when the soot would be produced,” said Faeth, “but predicting how much soot was much more difficult.”
The science team will now spend at least the next 12 months poring over information gained from the study. “There is a tremendous amount of data that comes out of each test,” said Faeth, “so there’s plenty to do.” Findings from the investigation may lead to a better understanding of how to contain unwanted fires, burn fuels more efficiently and reduce pollutants. “The study is a good example of a process found in a diesel engine,” said Faeth.
Later, Voss removed and stowed the soot experiment hardware and began preparing the Combustion Module for an investigation known as Structure of Flame Balls at Low Lewis Number, or SOFBALL. The study is designed to determine under what conditions a stable ball of flame can exist and if heat loss is responsible in some way for the stabilization of the flame ball during burning.
This experiment is designed to 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 investigator Dr. Paul Ronney of the University of Southern California in Los Angeles. “This is an acid test to show which, if any, current combustion models should be used.”
Three runs of the Droplet Combustion Experiment were completed overnight. The experiment is collecting information on burning rates of flames, flame structures and conditions under which flames are extinguished. The experiment involves burning a droplet of heptane fuel at different atmospheric pressures. Last night’s run was at one-half atmospheric pressure, half of that on Earth, in a mixture of helium and 25 percent oxygen.
“We had one excellent run,” said project scientist Dr. Vedha Nayagam of NASA’s Lewis Research Center in Cleveland, Ohio. “It is more difficult to ignite the droplets at lower pressure, but we think we have the procedure down now and it is just a matter of coordination. Timing is critical.”
Results of this investigation will also provide researchers with a better understanding of how combustion occurs and may lead to cleaner and safer ways to burn fuels as well as more efficient methods of generating heat and power on Earth.
In the TEMPUS levitating furnace facility last night, an experiment run was ended when the vapor levels reached the maximum amount allowed for the sample. The experiment is studying glass formation in zirconium-based metals. The experiment had been given additional run time, however, so although it ended early it completed the full originally scheduled run.
Later, Payload Specialist Dr. Roger Crouch performed a scheduled changeout of the TEMPUS side view camera, then activated an experiment to study the nucleation, or point at which solidification from the melted state begins, in liquid zirconium. During the experiment, the melts will be cooled below their freezing points. Researchers are interested in determining the temperatures at which nucleation occurs and how many nucleations occur at each temperature. Nucleation is an important chemical and industrial process.
Later, Crouch performed a shear cell rotation of the sample processing in the Large Isothermal Furnace. This procedure is part of an experiment to study the diffusion process of tracers, or impurities, in melted germanium, an element widely used as a semiconductor and alloying agent.
During the shear cell rotation, samples of pure germanium and germanium with an impurity are rotated into contact with each other. After an opportunity to mingle together, or diffuse, the resulting single sample is sheared into segments and cooled for post-flight analysis.
Findings from materials science experiments aboard Spacelab, including investigations under way in the TEMPUS and Large Isothermal Furnace facilities, may lead to improved techniques of processing materials on Earth and in turn better products.
This morning, Mission Specialist Dr. Donald Thomas is conducting a study of capillary- driven heat transfer devices in the Middeck Glovebox. The goal is to examine the performance of these devices in microgravity and improve their reliability. Similar devices may be used to transfer heat from electrical systems to radiators. Capillary heat transfer is attractive for use in space because it requires no power to operate and such devices cost less because they weigh less.
Payload Specialist Dr. Gregory Linteris is continuing to prepare the Combustion Module for the first SOFBALL test. Ahead, Linteris will initiate the second of six planned runs of the diffusion study under way in the Large Isothermal Furnace and complete a scheduled procedure to change out a disk of one of the microgravity measurement systems on board Columbia.
The next scheduled Public Affairs status report will be issued at approximately 6 p.m., July 8.
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