STS-73 Day 6 Highlights

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On Wednesday, October 25, 1995, 7:30 a.m. CDT, STS-73 MCC Status Report # 11 reports:

As the Blue Team was finishing up it's shift, Mission Specialist Mike Lopez- Alegria was interviewed by the NBC Newschannel. During the 5:23 a.m. CDT interview, Lopez-Alegria said the crew was well-adjusted to the onboard routine and "having a ball."

The Blue Team completed it's shift at 6:38 a.m. CDT and the Red Team -- Commander Ken Bowersox, Pilot Kent Rominger, Payload Commander Kathy Thornton and Payload Specialist Al Sacco -- is now on duty. During the Red Team shift today, Bowersox, Thornton and Sacco will all have a half -day off. Shuttle crew members are each given a day off to relax during long- duration shuttle missions such as STS-73. Bowersox and Thornton will have time off during the first part of the shift and Sacco will have time off during the later part of today's shift.

The port payload bay door on Columbia remains partially closed, about 51 degrees from fully open. However, at about 8:43 a.m. CDT, Bowersox will fully open the door. It will remain open for about one hour to allow for a dump of water from the condensate tank associated with the United States Microgravity Lab-2 module. The lab condensate tank collects water from dehumidifiers in the lab and must be dumped periodically, about each six days, during lab flights. The door is being opened during the dump to ensure there is ample clearance for the wastewater, which is ejected from a nozzle on top of the lab's forward end cone. Once the dump is completed, the door will again be closed partially to protect the radiators and cooling lines along its interior from debris impacts in orbit due to the shuttle's orientation and extended stay in space.

On Wednesday, October 25, 1995, 6 a.m. CDT, STS-73 Payload Status Report # 08 reports: (5/21:07 MET)

Overnight activities aboard the second United States Microgravity Laboratory were a balanced mix of crew-intensive fluid physics experiments and ground-controlled investigations into both fluid behavior and crystal growth.

At around 1 a.m. CDT, the Crystal Growth Furnace team finished solidifying a cadmium zinc telluride crystal for Principal Investigator Dr. David Larson of the State University of New York in Stonybrook. The furnace will be allowed to gradually cool until this afternoon.

Cadmium zinc telluride is used as a substrate, or base material, for infrared detecting crystals found in products such as cancer detection devices and the militaryÕs night- vision goggles. A similar crystal grown on USML-1 was a thousand times more defect-free than any comparable crystals ever grown on the ground. Larson hopes to demonstrate that the exceptional quality can be reproduced with the USML-2 sample.

"A sizable amount of effort and research money is going toward Earth-based efforts to improve substrate material," said Larson. The space-grown crystals will give researchers the opportunity to prove the widely held assumption that better substrate material would dramatically improve infrared detectors.

Mission Specialist Cady Coleman operated the Surface Tension Driven Convection Experiment. Initially, she lowered the level of silicone oil within the chamber to create a deeply concave surface. Later, she added oil until the surface rounded outward -- the experiment's first run with a convex surface. The size of the laser beam on the oil surface was adjusted to see how it affected the direction and nature of fluid flows, and the temperature was gradually increased to pinpoint when the flows began to oscillate. As they varied experiment conditions, ground team members saw a number of interesting oscillation patterns never observed in Earth- bound research under the influence of gravity. These observations will help scientists better understand manufacturing processes on Earth and how to improve them -- avoiding defects caused by unwanted flows when materials are cooled from a liquid or gaseous form.

With Coleman operating the surface tension experiment, Payload Specialist Fred Leslie practiced drop deployment in the Jet Propulsion Laboratory's Drop Physics Module. He then began the mission's first experiment for Principal Investigator Dr. Taylor Wang of Vanderbilt University in Nashville. A cheer went up from the science team as Leslie finally succeeded in the delicate process of inserting an air bubble inside a floating water drop. This experiment examines the fluid physics of the resulting liquid shell. It could lay the ground work for encapsulating living cells to treat hormonal disorders such as diabetes. An insulin- producing pancreatic cell could be injected into the body encased in a polymer shell, which would protect the cell from immunological attack and provide timed release of the drug.

"There are actually two factors at work in liquid spherical shells: fluid physics and chemical reactions," said Wang. "With these space experiments, we are able to separate them." Ground-based studies of these complex interactions are hampered by the small size of the drops which must be used and the constant motion induced by gravity. USML-2 experiments will allow experimentation with larger, stationary drops over a longer period of time.

The Geophysical Fluid Flow Cell team completed another six- hour run to simulate atmospheric conditions on the sun. They gradually stepped up the electric charge on the experiment to simulate the increase in gravitational force as the sun increases mass in later stages of its evolution. This instrument revealed several new types of convection on its first flight, Spacelab 3, in 1985. Improvements for USML-2, including real-time video data, should allow even greater insights into the often baffling fluid flows of complex stellar and planetary atmospheres.

On Wednesday, October 25, 1995, 6 p.m. CDT, STS-73 Payload Status Report # 09 reports: (5/09:07 MET)

A short period of leisure time was built into the schedule for the red shift science crew of the second United States Microgravity Laboratory (USML-2) mission today. Payload Commander Kathryn Thornton took her break in the morning, leaving Payload Specialist Al Sacco to enjoy his time off in the afternoon.

Sacco spent the first part of his shift working in the Glovebox facility on protein crystal growth experiments. Various proteins from laboratories around the world are being grown in this facility. Activating one of these protein crystal growth experiments involves mixing a selected protein solution with another solution, which activates growth. The crystals are then placed in an incubator facility at a precise temperature. Sacco today initiated new protein crystal growth experiments, based on his observations of previous sets of investigations. He adjusted experiment parameters in order to modify protein crystal growth conditions such as mixing procedures, crystal seeding, crystal mounting and crystal preservation.

Sacco brought on line the last of the 14 major experiment facilities during his morning shift. Marshall Space Flight Center's Suppression of Transient Accelerations by Levitation Evaluation (STABLE) is a test designed to isolate a small science experiment from high-frequency accelerations, including Shuttle operations and crew activity. The device uses a suspended platform controlled by electromagnetic actuators. Accelerometers on the platform provide data on Shuttle disturbances' data which allows position sensors to locate the platform with respect to the base, keeping the platform centered between disturbances. This greatly reduces accelerations and gives the experiment a smoother ride. An experiment known as CHUCK will debut on STABLE later in the mission.

Sacco continued work today in the Geophysical Fluid Flow Cell Experiment facility. The experiment uses a stainless steel hemisphere about the size of a baseball, surrounded by a sapphire hemisphere, with silicone oil between the two. By applying an electric charge to the hemispheres, a crew member creates artificial gravity. Other parameters changed with each run are the temperature of the silicone oil and the speed of the hemispheres' rotation. In this way, a variety of fluid flows in oceans, planets and stars are mimicked, possibly helping forecast ocean flows and weather patterns. According to Principal Investigator Dr. John Hart, "We've already discovered several interesting things, and we've been able to modify our experiment operations and investigate things we wouldn't have been able to do otherwise."

Pilot Ken Rominger and Sacco kept a close check on growing zeolites in the Zeolite Crystal Growth furnace today. Zeolites are inorganic compounds of aluminum, silicon and oxygen whose porous structures make them valuable catalysts and purifiers for the chemical processing industry.

"We want to learn more about how zeolites nucleate and grow, and more about their structure, so we can apply that knowledge to different processes on Earth," said Co-principal Investigator Dr. Nurcan Bac of the Worcester Polytechnic Institute. "For instance, one of the zeolites in this experiment is widely used by the petroleum refining industry to crack heavy oils into gasoline. If we can increase the efficiency of this type of zeolite, we could get more refined petroleum products from the same amount of crude oil."

Near the end of his shift, Sacco conducted a purge of the argon gas in the Crystal Growth Furnace. Sacco vented the gas then pumped fresh argon into the experiment chamber. This prepared the furnace for the third crystal to be grown in the facility on USML-2: a sample of gallium arsenide, a semiconductor material. Gallium arsenide crystals are valuable for use in electronic devices and a variety of other products. Provided by the Case Western Reserve University, the experiment principal investigator is Professor David Matthiesen, also an alternate payload specialist for USML-2.

This crystal of gallium arsenide will enable scientists to refine techniques for more uniformly distributing a dopant, or impurity, during growth. Impurities are added to these semiconductor compounds to improve or precisely control their electronic characteristics. To produce high quality gallium arsenide crystals, scientists need to understand the process by which these impurities are distributed within the compound during crystal growth.

Sacco set up the Surface Tension Driven Convection Experiment, getting it ready for Thornton to begin experiment runs after her break. While Thornton conducted constant temperature baseline tests on the fluid's curved surface, creating a variety of kaleidoscope-like patterns in the oil, video was downlinked to investigators on the ground. They periodically relayed commands to Thornton to increase or decrease temperatures across the surface of the fluid, allowing investigators to study the transition from stable fluid flows to the more unstable ones that result when the temperature is increased. One key factor prompting this research is that unwanted fluid flows can create defects in the production of high-tech crystals, metals, alloys and ceramics. Thus investigators are seeking to understand how and why they occur.

On Thursday, October 26, 1995, 5 p.m. CDT, STS-73 MCC Status Report # 12 reports:

Columbia's crew members participated in two special events during their sixth flight day as the orbiter itself continued to perform problem-free as did science investigations underway in the Spacelab. Early Wednesday Mission Specialist Michael Lopez-Alegria participated in an interview with NBC Newschannel. Also on Wednesday, STS-73 crew members gathered in the shuttle's middeck and taped the ceremonial first pitch that will open Game Five of the World Series Thursday night in Cleveland, Ohio. The taped message and the first pitch will be played on the "Jumbotron" screen at Jacobs Field in Cleveland and viewed by a nationwide audience on ABC-TV. Commander Ken Bowersox wished the Atlanta Braves and the Cleveland Indians good luck before he threw the slow-spinning pitch, marking the first time a World Series first pitch thrower has not been in the ballpark to make the pitch. Columbia's astronauts will sign the on-board baseballs and give them to Major League Baseball to be enshrined in the Baseball Hall of Fame in Cooperstown, N.Y.

Crew members on the Red Team mark the end of their work day at 6:38 p.m. CDT and will return to their work shift in the Spacelab at 6:38 a.m. Columbia is in a 169 by 164 statute mile orbit, completing a revolution of the Earth each 90 minutes.

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