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Friday, July 11, 1997, 7 a.m. CDT
STS-94 Mission Science Report # 17s

Now entering day 11 of the Microgravity Science Laboratory mission, crew members and science teams are reporting steady growth of good returns with their investigations. “Science teams are getting everything they hoped for, and in some cases, more than they hoped,” said Mission Manager Teresa Vanhooser of NASA’s Marshall Space Flight Center in Huntsville, Ala. “We’re seeing a lot of smiling faces in the science operations areas.”

The flame ball experiment is one that is yielding good results. The experiment, being conducted in the Combustion Module experiment facility aboard Spacelab, studies the burning processes of very weak mixtures of fuel and air in weightlessness. The diluted mixtures are so weak they will not burn under the influence of Earth’s gravity.

Last night, Payload Commander Dr. Janice Voss completed one burn and attempted another. The first run resulted in two flame balls that burned for almost the entire 500-second duration of the test. The mixture didn’t ignite on the reburn. “This is not surprising,” said lead scientist Dr. Paul Ronney of the University of Southern California in Los Angles, “since the flame balls in the first run burned out before the duration, which means they consumed most of the fuel available to them.”

The investigation is providing researchers with a better understanding of the combustion process and may be used to improve theoretical models. “Not much is known about the burning processes of these mixtures,” said Ronney. “So we are trying to see which, if any, theoretical models should be used.” Results from the experiment may also lead to increased fuel efficiency and reduced emissions in combustion engines, and improvements in fire safety which would benefit the mining, chemical manufacturing and aerospace industries.

Payload Specialist Dr. Roger Crouch performed an experiment in the Middeck Glovebox last night to study the manipulation of bubble movement and shape in water. During the experiment, an air bubble is deployed into a water-filled chamber. Sound waves are used to distort the shape of the bubble, and instruments record the bubble’s movement as the shape of the bubble changes. Researchers will use this information to gain a better understanding of fluid physics and improve theoretical models which describe these fundamental processes.

Late last night, crew members began a procedure to fix the top-view camera in the TEMPUS levitating facility. The camera stopped working earlier in the mission. Crew members were unable to complete the procedure because they could not remove all the screws from the panel covering the camera. The crew and science team are continuing to troubleshoot the problem.

Pilot Susan Still performed a shear cell rotation of a sample processing in the Large Isothermal Furnace. This procedure is part of a study examining 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 doped germanium, or one with an additive, 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. Fundamental measurements taken from the segments may have applications for improving semiconductors used in electronic components.

Linteris began his shift early this morning working in the Droplet Combustion Apparatus, a facility designed to accommodate a study of burning fuel droplets. “We are burning heptane fuel droplets at different pressures over a range of atmospheric concentrations to map the burning characteristics of the droplets, to learn what is happening,” explained Dr. Vedha Nayagam of NASA’s Lewis Research Center in Cleveland, Ohio. The run conducted this morning was at one-half atmospheric pressure, half of that on Earth, in a 30-percent concentration of oxygen. “Everything went great,” said Nayagam. “We got some really fantastic runs.”

The study is providing researchers with fundamental knowledge of the burning process and may provide a method for verifying which complex, chemical model accurately describes the process. It may also lead to cleaner and safer ways to burn fuels.

Thomas spent the morning preparing to conduct an experiment in the Middeck Glovebox. The experiment studies the burning process of single, large fuel droplets. A thin fiber is used to position the large fuel droplets in the viewing area. The droplets are ignited and the burning characteristics, such as burn rates, flame positions and the diameters of the droplets at the time the flames are extinguished, are measured. The study also investigates how the burning process is influenced by convection, or the transfer of heat caused by motion in the air. Results from this study may lead to a better understanding of the combustion process and its by-products, such as soot, a harmful pollutant.

Coming up, Linteris will complete the series of runs under way in the Droplet Combustion Apparatus before beginning another test of the flame ball experiment. Thomas will begin the Fiber Supported Droplet Combustion experiment in the Middeck Glovebox. Later, he will initiate another study of undercooled metallic alloys in the TEMPUS levitating facility. Undercooling is when a liquid is cooled below its normal freezing point and still remains a liquid. This TEMPUS investigation will study nucleation, or the point at which solidification from the melted state begins.

The next scheduled Public Affairs status report will be issued at approximately 6 p.m., July 11.


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