STS-94 Mission Science Report # 19s
Saturday, July 12, 1997, 7 a.m. CDT
The Shuttle Columbia crew and the Microgravity Science Laboratory are rounding the final turn and heading into the home stretch of their 16-day run of conducting science in space. According to Mission Scientist Dr. Mike Robinson, things continue to go well. “The science teams have been working very hard, and they’re happy with what they’ve seen so far,” said Robinson.
The science team for the flame ball experiment was happy with what it saw last night, reporting two more series of successful runs. The investigation, being conducted in the Middeck Glovebox, examines the combustion properties of very weak fuel mixtures in near-zero gravity. Payload Commander Dr. Janice Voss completed one set of runs last night and Payload Specialist Dr. Gregory Linteris completed another early this morning. “The experiment is going extremely well and the science team is getting fantastic data,” said lead investigator Dr. Paul Ronney of the University of Southern California in Los Angeles.
During the experiment, the chamber is filled with very weak combustible gases, the mixture is ignited with a spark, and information is gathered on the resulting flame balls. “We’re interested in learning which mixtures will burn and which ones won’t,” said Ronney, “and the limits of combustion -- where the weakest possible flames can exist.”
Also, Ronney reported that during last night’s burns, instruments measured very little disturbance in the microgravity environment of the test facility. “The flame is being driven by hot gases surrounding the flame and these gases are extremely sensitive,” said Ronney, “so it’s important to minimize disturbances in the environment.”
Since little is known about the burning processes of these flames, findings will be used to verify which, if any, existing theoretical models are accurate. “We want a steady flame so we can easily compare it to computer models on the ground,” said Ronney. “Any disturbances make that comparison more difficult.”
Another combustion science experiment, which studies the burning process of large fuel droplets, was conducted in the Middeck Glovebox. Payload Specialist Dr. Roger Crouch completed a series of tests last night and another series was completed this morning by Mission Specialist Dr. Donald Thomas. “We are ahead of schedule,” said investigator Dr. Ron Colantonio of NASA’s Lewis Research Center in Cleveland, Ohio. “We’ve been able to complete a few extra runs and we’re getting good science.”
During the experiment, a thin fiber is used to position a large droplet of fuel in the viewing area of the chamber. The droplet is then ignited and information is gathered on the burn rates, flame shape and radiation emitted. “The amount of energy lost through radiation has never been measured before,” said Colantonio. “People have guessed what that is. We’re actually going to measure it.”
Information from this study can also help improve theoretical models of combustion. It will also complement what is being learned from the Droplet Combustion Experiment, also being conducted aboard Spacelab. That experiment is studying the burning processes of heptane fuel droplets. Like the Droplet Combustion Experiment, the Fiber Supported Droplet experiment also burns heptane fuel droplets, but in an environment of oxygen and hydrogen, rather than oxygen and helium. “By changing one parameter, we will be able to measure the effect of the different combinations of elements in the environment,” said Colantonio. “This will be very beneficial to the Droplet Combustion science team.”
Overnight, two shear cell rotations of the sixth and final run of an investigation to study the diffusion process of tracers, or impurities, in melted germanium were conducted. Crouch performed the first rotation last night and a second rotation was performed by Pilot Susan Still early this morning. “It looks like we saved the best for last,” said lead scientist Dr. David Matthiesen of Case Western Reserve University in Cleveland, Ohio. “We’re optimistic the results of this test will be good.”
The experiment involves two samples, one of pure germanium and one of germanium with an additive. The first shear rotation brings samples into contact with other. After diffusing, or mixing, for a certain amount of time, the resulting single sample is sheared into segments and cooled for post-flight analysis.
Germanium is an element widely used as a semiconductor. Knowledge gained from this study may be used to improve the performance of electronic components made from semiconductor materials, such as transistors and integrated circuits.
Last night in the TEMPUS facility, Crouch initiated an experiment to measure the surface tension and viscosity of undercooled liquid metals. During the experiment, an electromagnetic pulse is used to squeeze, then release a sample -- in this case, liquefied gold -- being levitated in the facility. Researchers then gather information on the oscillations, or changes in the sample’s shape. From these measurements researchers are able to determine the surface tension and viscosity -- or resistance to flow -- of the sample. This is a new technique which is allowing researchers to measure some of the fundamental properties of liquid gold for the first time.
One aim of the investigation is to achieve improvements in materials processing techniques on Earth, in turn making possible better products.
Ahead, Thomas will continue to conduct the Fiber Supported Droplet Combustion experiment in the Middeck Glovebox and Linteris will begin the third phase of the Droplet Combustion Experiment. This phase of the study is designed to map the burning characteristics of a heptane fuel droplet at one-quarter atmospheric pressure, a fourth of the atmospheric density on Earth, at varying oxygen concentrations.
The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 13.
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