STS-94 Mission Science Report # 7s
Saturday, July 5, 1997, 6 a.m. CDT
As America celebrated the country’s birthday, the crew of Microgravity Science Laboratory -1 mission set off its own special fireworks. For the past 24 hours, combustion experiments aboard Columbia have been the main focus of science activity in the Spacelab.
Yesterday, three series of burning fuel droplet runs were completed in the Droplet Combustion Apparatus. Payload Specialist Dr. Gregory Linteris completed one series Friday morning and then another during his next shift -- early Saturday. Payload Commander Dr. Janice Voss completed one series run Friday afternoon.
During the experiment a heptane fuel droplet is burned in an atmosphere of helium and oxygen. The droplet is formed and deployed in the apparatus. Igniter wires are touched to the sides of the droplet then retracted to create a free burning droplet.
“We look at the flame location, the diameter of the droplet and soot production,” explained lead scientist Dr. Forman Williams of the University of California at San Diego. “Droplet burning occurs in spray combustion, such as in diesel engines, and is relevant to power production and the burning of fossil fuels.”
Yesterday and early this morning, crew members worked in Middeck Glovebox to conduct the Fiber Supported Droplet Combustion experiment, also led by Williams. The experiment studies the burning process of single, large fuel droplets. Mission Specialist Dr. Donald Thomas completed a series of tests yesterday morning burning methanol and ethanol fuel droplets. Payload Specialist Dr. Roger Crouch completed a series of tests last night burning droplets of a mixture of methanol and water.
A thin fiber is used to position the large fuel droplets in the viewing area. Once the drops are ignited, researchers measure characteristics, such as burning rates, flame positions and the diameters of the droplets at the time the flames are extinguished. 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 increased fuel efficiency and a reduction in air pollutants on Earth.
In the Combustion Module --1, two runs the Laminar Soot Processes experiment were completed Friday. Linteris completed one test just before noon and Voss completed another last night. Both studied the burning of an ethylene-fueled flame. The soot investigation is gathering information on flame shape, the type and amount of soot produced under various conditions and the temperature of soot components.
As principal investigator Dr. Gerard Faeth of the University of Michigan in Ann Arbor explains, it would be very difficult to conduct this experiment on Earth. “Imagine a campfire;” said Faeth, “the yellow color of the fire is soot. But the fire is burning very fast and sparks are shooting out in all directions. Obviously, not the ideal environment for studying soot.”
Findings from this investigation may lead to a better understanding of how to contain unwanted fires and limit the number of fatalities from carbon monoxide emissions.
Before the end of his shift yesterday at noon, Thomas completed a disk change-out of the Quasi-Steady and Space Acceleration Measurement system. The system is one of four on board the Shuttle which detects and records the small, yet unavoidable disturbances in the near-zero gravity environment of the Spacelab. Science teams rely on the information, down-linked in near-real-time, to determine the effect of the disturbances on experiments.
Late Friday afternoon, Crouch activated an experiment in the electromagnetic containerless processing facility, called TEMPUS. “We’ve had a very successful experiment run, collecting a wide variety of data on the properties of our sample and its ability to freeze or solidify. This is important to our understanding of theoretical models of liquid crystallization and to processing metallic-glass materials,” said principle investigator Dr. W.I. Johnson of the California Institute of Technology in Pasadena, Calif.
The TEMPUS investigation is designed to measure the thermophysical properties -- heat capacity, thermal conductivity, nucleation rates, surface tension, viscosity and thermal expansion -- of glass-forming metallic alloys. Findings from the experiment using a zirconium-titanium alloy may improve ground-based techniques for processing materials and in turn improve materials and products.
Later, Crouch removed a sample run of the Liquid Phase Sintering Experiment from the Large Isothermal Furnace and initiated the next run of this investigation. During the experiment, compressed powders of tungsten, nickel, iron, tungsten, nickel and copper are heated to 1,500 degrees Celsius. When heated, the nickel, iron and copper melt but the tungsten does not. This forms a solid-liquid mixture. Researchers are using these mixtures to study the sintering process, or how these particles bond when heated.
“On Earth, these mixtures settle out and sintering results in a distorted material,” explained lead scientist Dr. Randall German of Pennsylvania State University in University Park. “How to make materials of the right shape and size with no distortion is fundamental to powder metallurgy, so we are learning why distortion occurs on Earth.”
Early this morning after the sintering sample had finished processing in the Large Isothermal Furnace, Thomas removed it and initiated a study to establish an accurate measurement of the diffusion coefficient -- a fundamental quantity which describes the diffusion process -- of liquid tin in relation to temperature.
On Earth, diffusion experiments conducted at high temperatures have been unsuccessful due to fluid movement caused by gravity. This experiment, led by Dr. Toshio Itami of the Hokkaido University in Sapporo, Japan, may help researchers more clearly define the diffusion process and could lead to improved processing techniques and products on Earth..
Later, Thomas set up the Bubble and Drop Nonlinear Dynamics experiment -- led by Dr. L.G. Leal of the University of California at Santa Barbara -- in the Glovebox. Results could lead to techniques that eliminate or counteract the complications that bubbles cause during materials processing.
Ahead, Thomas will perform the Bubble Drop and Non-linear Dynamics experiment in the Glovebox and Linteris will continue the combustion studies --conducting more runs of the Droplet Combustion Experiment.
The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 6.
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