STS-94 Mission Science Report # 7s
Friday, July 4, 1997 8 a.m. CDT
Through the evening and into the morning on Friday, Space Shuttle crew members and ground controllers worked together to complete a variety of experiments and resolve some of the challenges associated with keeping a complex science payload up and running. The Microgravity Science Laboratory consists of more than 30 experiments in the primary areas of combustion, biotechnology, materials science and fluid physics.
“Great teamwork by the orbiter crew and science teams on the ground has worked around some anomalies enabling us to collect very valuable science data,” said Dr. Patton Downey, assistant mission scientist.
Aboard Columbia, runs of the Droplet Combustion Experiment were slightly delayed while troubleshooting teams investigated a suspected correlation between three brief malfunctions of the computer which oversees all the experiments aboard Spacelab. Within minutes of each malfunction, the crew was able to reboot the computer with no impact to science.
Meanwhile, Payload Commander Dr. Janice Voss performed another run of the soot experiment in the Combustion Module - 1 that had originally been slated for Payload Specialist Dr. Roger Crouch. Shifting the schedule allowed Crouch to perform the Internal Flows in a Free Drop experiment that had been scheduled for a later time.
Crouch began the experiment in which free drops of liquid are deployed and manipulated in the Glovebox using sound waves. Attempts to deploy the drops were, however, unsuccessful. The science team on the ground suspects that a change in the alignment of the liquid injector may have been the cause of the unsuccessful drop deployment and is troubleshooting the problem.
Before the end of his shift, Crouch performed a sample exchange in the Large Isothermal Furnace, initiating the second run of the Liquid Phase Sintering experiment, which is led by Dr. Randall German of Pennsylvania State University in University Park, Pa.
In industry, the liquid phase sintering process is used to form very hard and dense solids -- which, in turn, are used to manufacture products such as cutting tools, car transmission gears and radiation shields. The sintering process involves heating metal or ceramic powders. Under high pressure and temperature, the powder grains liquefy and bond to form strong shapes, such as tools. On Earth, gravity affects the dispersal of the powders and causes the resulting solid to be less uniform. Investigators hope to better understand this process and develop techniques that can be used to lower costs of production and create even better sintered materials.
In the electromagnetic processing facility known as TEMPUS, an experiment to further the understanding of the fundamentals of undercooling and formation of metallic glass was initiated around 10:00 p.m. (CDT) Thursday. The facility uses a combination of an electromagnetic field and the microgravity environment to suspend metal alloys in a free space within a set of coils. Within the coils, the suspended alloy may be melted and resolidified in an ultra- pure environment. The sample of zirconium-nickel was cycled through two stable melting and solidification runs, then became molten and contacted the side of the sample container, adhering there. The experiment run was then terminated and the sample was removed.
“Before the sample stuck to the coils, we were able to get some good data,” said the principal investigator, Dr. Hans Fecht of the Technical University in Berlin, Germany. The experiment team is evaluating data concerning the unexpected contact and sticking. The next TEMPUS experiment run is scheduled for later this afternoon.
Before the handover from the on-board blue shift science crew to the red shift, teams on the ground determined that the apparent cause of earlier glitches with the Experiment Control Computer System was data transmission from the Droplet Combustion Experiment. Transmission of this data was disabled and the droplet combustion team -- commanding the experiment from the ground -- resumed the combustion investigation which resulted in several “good burns,” according to researchers.
Voss and Crouch handed off to Mission Specialist Dr. Donald Thomas and Payload Specialist Dr. Gregory Linteris around 1:00 a.m. (CDT).
After his daily planning session, Payload Specialist Dr. Greg Linteris began the first of several runs of the Droplet Combustion Experiment. The experiment takes place in a specially designed enclosed chamber in which single droplets of heptane fuel can be burned in an atmosphere composed of a mixture of helium and oxygen. The droplet is formed by injecting heptane through two injectors on opposite sides of the test platform within the chamber. Once the drop is formed, the injectors are retracted and the drop is then ignited by two hot-wire igniters that are brought near the droplet from opposite sides. The burning droplets observed and recorded using video cameras and high-resolution photographs. The investigators will study these recordings to obtain data about the physical and chemical processes that take place in droplet combustion, including conditions under which the flames extinguish, the chemistry of the combustion reaction, and the production of pollutants such as nitrogen oxides and soot particles.
“We can’t get this information from ground-based experiments,” said principal investigator Dr. Forman Williams of the University of California at San Diego. “For the first time, we’re burning free fuel droplets.” 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.
Around 3:45 a.m. (CDT) Friday, Thomas set up another combustion study led by Williams --the Fiber Supported Droplet Combustion investigation. During the experiment, single large droplets of fuel are ignited to study how fuel burns and test a new technique of droplet deployment using thin fiber material.
To burn large fuel droplets -- even in the near-weightless environment of space -- it is necessary to have a support mechanism for the drops of fuel. Otherwise the burning drop may move around, hit the walls of the container or move out of the camera's field of view.
The Fiber Supported Droplet Combustion experiment allows combustion investigators to study the burning of fuels -- such as n-heptane, n-decane, methanol, ethanol, methanol/water mixtures and heptane/hexadecane mixtures -- in droplets as large as nearly one-quarter-inch diameter. Additionally, the experiment will shed light on the role that convection plays in burning by introducing a controlled air- flow into the flame environment during the experiment.
As the red shift crew continues its 12-hour duty day, Thomas and Linteris will perform further combustion studies aboard Columbia -- including runs of the Fiber Supported Droplet Combustion Experiment and the Droplet Combustion Experiment.
The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 5.
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