STS-94 Day 10 Highlights

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On Thursday, July 10, 1997, 6:00 a.m. CDT, STS-94 MCC Status Report # 18 reports:

More than one week into the STS-94 mission, the seven crewmembers aboard Columbia are continuing their around-the-clock science investigations in the Spacelab module, focusing on how various materials and liquids change and behave in a microgravity environment.

After a brief handover with their blue team counterparts just after midnight, the red team members -- Commander Jim Halsell, Pilot Susan Still, Mission Specialist Don Thomas and Payload Specialist Greg Linteris -- took over responsibility for the management of science operations aboard the Shuttle.

About the same time as the red team began their Flight Day 10 activities, NASA astronaut Michael Foale, aboard the Russian Mir space station, received a phone call from NASA Administrator Daniel Goldin. During their conversation, Foale talked about the activities he and his two cosmonaut crewmates have been engaged in since a Progress vehicle collided with the Spektr science module last month. Foale showed some of the hardware that will be used later this month, during an intervehicular spacewalk, to restore power connections to the 3 undamaged Spektr solar arrays.

Aboard Columbia, Halsell continued with his status checks and video documentation on some of the Microgravity Science Laboratory (MSL) experiments while Still monitored various orbiter systems. The two science members of the red team, Thomas and Linteris, continued their efforts with the 30-plus different experiments being carried in the Spacelab module. Thomas' efforts this morning were with the Glovebox unit and the Bubble Drop & Nonlinear Dynamics experiment while Linteris worked with the Droplet Combustion Experiment.

Thomas and Linteris are both scheduled for a half day of off-duty time this afternoon. Half day rest periods are built into the crew schedule during long duration spaceflights like STS-94 so that the astronauts can remain well rested and operate at peak efficiency.

While he is relaxing this afternoon, Thomas will take a few minutes to talk with high school students from the greater Cleveland area who will be gathered at the Great Lakes Science Center. The conversation between Thomas and the students is scheduled for 11:22 a.m. CDT.

The STS-94 Blue team, Payload Commander Janice Voss, Mission Specialist Mike Gernhardt and Payload Specialist Roger Crouch, will be awakened just after 11 a.m. today, to start their next day of orbiter and science operations. The blue team will take over responsibility for science and orbiter operations shortly after 1 p.m.

On Thursday, July 10, 1997, 7:00 a.m. CST, STS-94 Payload Status Report # 15 reports:

The crew of the Microgravity Science Laboratory mission and science teams on the ground worked steadily through the night, continuing to conduct fundamental scientific research in the areas of combustion science, fluid physics, materials science and biotechnology.

Payload Commander Janice Voss worked in the Combustion Module last night to conduct an experiment to study the burning processes of very weak mixtures of fuel and air in low-gravity. During the experiment, a mixture of hydrogen, oxygen and sulfur hexafluoride -- a combination that does not readily ignite -- was used in the facility. "We were able to get it to burn. The burn and reburn were both extremely successful," said investigator Paul Ronney of the University of Southern California in Los Angeles. This is significant because these are the weakest flames ever burned. They are will not burn on Earth.

Findings from this study may be used to build better models of weak combustion processes which may be applied to the design of cleaner, more efficient-burning fuel engines. "We know that if we can burn weaker mixtures in our engines, we could indeed get higher fuel efficiencies, with lower pollutant formation," said Ronney.

Overnight, Payload Specialist Dr. Roger Crouch and Mission Specialist Dr. Donald Thomas conducted two tests of the Bubble and Drop Nonlinear Dynamics experiment in the Middeck Glovebox. During the experiment, acoustic pressure, or sound, is used to position the bubble in the center of a water-filled container and then flatten it. Researchers are measuring the bubble's movement as the shape of the bubble changes. "This reveals the mechanical properties of the bubble under large forces, or distortions," said investigator Dr. Anthony Hmelo of Vanderbilt University in Nashville, Tenn. "These properties are very difficult to model, so we are conducting this study to better understand fluid physics in general and improve theoretical models."

Findings from this investigation may also have applications for improving industrial processes. "There are a range of industrial processes that depend on drops for operation," said Hmelo. "For instance, the combustion of fuels, the same processes being studied in other experiments aboard Spacelab, depends on the kinds of fluid physics we are investigating in the Middeck Glovebox."

Crouch performed a scheduled disk change-out in the Quasi-Steady and Space Acceleration Measurement system. The system is one of four on board the Shuttle which detects and records the small, unavoidable disturbances in the near-zero gravity of the environment of the Spacelab. Science teams rely on the information, downlinked in near-real-time, to determine the effect of the disturbances on experiments.

In the Large Isothermal Furnace last night, Crouch began the fourth of six planned runs of an experiment to study the diffusion process of tracers, or impurities, in molten semiconductors. Diffusion is the process by which liquid metals mix without stirring. The experiment is a fundamental scientific study to measure the thermophysical properties of germanium, an element widely used as a semiconductor. Findings from the study may have applications for improving the performance of electronic components made from semiconductor materials, such as transistors and integrated circuits.

Early this morning, Payload Specialist Dr. Gregory Linteris reported "fantastic" burns in the Droplet Combustion Experiment. During the experiment, heptane fuel droplets are burned at different pressures and oxygen concentrations. Runs conducted this morning were at one-half atmospheric pressure, half of what it is one Earth, in oxygen concentrations varying from 25 to 40 percent.

Results of each test may be different depending on the pressure, oxygen and size of the droplet. "Three things can happen," said project scientist Dr. Vedha Nayagam of NASA's Lewis Research Center in Cleveland, Ohio. "The droplet can not ignite; it can ignite and burn out partially, leaving a droplet of fuel; or it can ignite and consume the droplet, burning out completely." The Droplet Combustion Experiment is studying these scenarios.

The experiment is also interested in determining the complex chemical processes which occur when the flames are extinguished. "By understanding the chemistry which occurs, we can burn them more cleanly, more efficiently, because we know how they work," said Nayagam.

Later, Linteris began an experiment in the TEMPUS levitating furnace facility to collect fundamental measurements of an undercooled sample of palladium-silicon. Undercooling is when a liquid remains fluid when cooled below its freezing point. During the experiment an electromagnetic pulse is used to squeeze, then release the sample being levitated in the facility. Researchers then gather data on the oscillations, or changes in the sample's shape. "By measuring the oscillations, we can determine the surface tension and viscosity, or resistance to flow," said researcher Bob Hyers of the Massachusetts Institute of Technology in Cambridge, Mass.

"We are using a new technique which is allowing us to measure the viscosity of these samples for the first time, measurements which can't be obtained on Earth. And even some of the surface tension measurements are a first," said Hyers. This information may be used to improve materials processing techniques on Earth and in turn products manufactured from these processes. "The study is providing us with fundamental measurements for modeling industrial materials systems. Without the right parameters, you can't model systems," said Hyers.

Ahead, Linteris will continue to conduct the Droplet Combustion Experiment and the fifth run of the diffusion of molten semiconductors experiment will be initiated in the Large Isothermal Furnace.

On Thursday, July 10, 1997, 5:00 p.m. CDT, STS-94 MCC Status Report # 19 reports:

Science activities are continuing on board Columbia as the seven-member crew supports a steady pace of investigations focusing on flames, combustion, and plant growth on orbit.

After a brief handover with their red team counterparts about 1 p.m. central time today, the blue team astronauts - Payload Commander Janice Voss, Mission Specialist Mike Gernhardt and Payload Specialist Roger Crouch - assumed responsibility for the management of science and orbiter operations.

Throughout the afternoon and evening hours, Voss and Crouch will support investigations in the Combustion Module and Glovebox facilities, while Gernhardt monitors orbiter systems and conducts video documentation of Spacelab operations. Late in the red team's day, Gernhardt and Crouch will take time out from their investigations for an interview with the CBS program "Up to the Minute." That interview is expected to occur about 12:15 a.m. central time Friday.

Before relinquishing responsibility to the blue team, the four-member red team of astronauts completed another day of scientific investigation. Mission Specialist Don Thomas and Payload Specialist Greg Linteris both enjoyed some scheduled off-duty hours this morning, to ensure they remain well rested during this planned 16-day mission. Thomas took a few minutes this afternoon to talk with students who gathered at the Great Lakes Science Center in Thomas' hometown of Cleveland. Thomas answered questions about his preparations for the STS-94 mission, the science he is conducting on board, and his Ohio roots.

The red team astronauts -- Commander Jim Halsell, Pilot Susan Still, Thomas and Linteris -- will be awakened just after 11 p.m. today to start their next day of orbiter and science operations.

Columbia is continuing to fly virtually trouble-free, providing a stable platform for science operations.

On Thursday, July 10, 1997, 6:00 p.m. CST, STS-94 Payload Status Report # 16 reports:

The study of fire dominated the Microgravity Science Laboratory-1 investigations in Columbia's Spacelab, today.

This morning Payload Specialist Dr. Greg Linteris completed a run in the second phase of the Droplet Combustion Experiment. The run is part of a three phase study to map the burning characteristics of heptane fuel droplets over a range of atmospheric pressures. The first phase --conducted earlier in the mission -- burned fuel droplets at one atmospheric pressure, the same as on Earth. The second phase burned the droplets at one-half atmospheric, while the third will burn droplets at one-quarter atmospheric pressure.

"In each phase, we are keeping the pressure the same and slowly reducing the oxygen to see if the fuels can still burn and if so, how they burn," said project scientist Dr. Vedha Nayagam of NASA's Lewis Research Center in Cleveland, Ohio. "On Earth, we encounter low combustion scenarios -- for instance, in gas turbines -- so it's important to know what happens when pressure is reduced."

"We wanted to expand our data base at one-half atmospheric pressure," said co-investigator Dr. Fred Dryer of Princeton University in Princeton, New Jersey, "so we combined two of our gas bottles that had been slated for one-quarter atmospheric pressure studies to yield a one-half atmospheric condition in the test chamber." The one-quarter atmospheric runs are scheduled for later in the mission.

Linteris burned three sizes of heptane droplets -- 4 mm, 3 mm and 2 mm. The 4 mm droplet extinguished after burning 5.9 seconds--leaving behind a relatively large droplet. The smallest droplet burned about nine seconds -- using almost all of the fuel.

"The large droplet extinguished early in its burn time due to loss of significant combustion energy by radiation," said Dryer. "The small droplet burned to near completion because less energy is lost by radiation as the droplet's initial diameter is decreased. We would have received opposite results if we'd conducted this same experiment on Earth."

Basic knowledge gained by the mapping of these various burning regimes will be used by scientists to design better combustion systems, such as combustors and propulsion systems, to extract maximum efficiency while minimizing unwanted pollutants.

After Linteris completed the series of runs to study burning fuel drops, both he and Mission Specialist Dr. Don Thomas took a planned half-day break.

Late this morning, a palladium-silicon sample completed an 11-hour processing period in the TEMPUS levitating furnace facility. The sample went from a solid state to a molten state and then was undercooled 16 times. The co-investigator, Bob Hyers of the Massachusetts Institute of Technology in Cambridge, Massachusetts, said this particular sample was chosen because it is a glass forming metal with many industrial applications.

"Preliminary results look very promising," said Hyers. "We got a wide range of temperatures and achieved a reasonable amount of undercooling."

A sample of palladium copper and silicon is now processing in the levitation furnace. Knowledge gained from this study, led by Dr. Ivan Egry of the German Aerospace Research Establishment in Cologne, may be used to improve materials processing techniques on Earth, and in turn, products manufactured from these processes.

Early this evening Payload Commander Dr. Janice Voss performed a run of the flame ball experiment using a 4 percent hydrogen in air fuel mixture. "The rich fuel mixture matches the lean flammability limit of combustion on Earth," said project scientist Dr. Karen Weiland of NASA's Lewis Research Center in Cleveland, Ohio.

Voss' sparking attempt resulted in eight flame balls. By studying flame balls, scientists hope to understand the physics of near-limit combustion, thereby leading to the design of leaner-burning fuels and improvements in engine efficiency - along with reduced emissions. The Structure of Flame Balls at Low Lewis-number experiment is led by Dr. Paul Ronney of the University of Southern California in Los Angeles.

This afternoon, Payload Specialist Dr. Roger Crouch performed the Bubble Drop and Non-linear Dynamics Experiment led by Dr. L.G. Leal of the University of California at Santa Barbara. During the experiment, Crouch deployed a bubble into the center of a water-filled container and then flattened it. On the ground the science team measured the bubble's movement as the shape of the bubble changed--revealing mechanical properties of the bubble under large forces or distortions. Later, Crouch will deploy two bubbles and try to create one bubble from the two--shedding light on bubble control and manipulation. Results of the bubble experiment could lead to techniques that eliminate or counteract the complications that bubbles cause during materials processing.

Processing of a germanium sample to study diffusion processes in molten semiconductors ended this morning when the control thermocouple, or temperature sensor on the sample, malfunctioned. The sensor inadvertently told the furnace to heat the sample beyond the high temperature limit which caused the Large Isothermal Furnace to shut itself off. The furnace is designed to monitor temperature and will shut off automatically if a sample reaches a certain temperature. The science team on the ground says the Large Isothermal Furnace is operating normally, and are assessing the control thermocouple which is part of this particular sample run. The orbiter crew initiated another scheduled sample run of the experiment at 5:15 p.m. -- after the furnace had cooled down. This run is proceeding normally.

Ahead, Voss will conduct another run of the flame ball experiment and Crouch will continue the bubble experiment.

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