Search Johnson


Johnson News

Text Size

Wednesday, July 9, 1997, 6 p.m. CDT
STS-94 Mission Science Report # 14s

“Great Balls of Fire” are just what Columbia’s science crew saw today in an experiment to study the simplest form of combustion. But it wasn’t their strength or size that made these flame balls great. The astronauts were continuing an experiment that is resulting in the weakest flames ever produced.

Most of the fuel mixtures that are being used for this experiment are so weak -- resulting in flames that are about one hundred times weaker than a common match flame -- that they will not burn on Earth.

Knowledge gained from this experiment will be used to build better computer models of weak combustion that can be applied to the design of more fuel efficient and cleaner engines. Researchers will also be able to apply experiment results to spacecraft safety.

“We’re learning that there are certain types of fuel mixtures that will burn in a space environment that couldn’t burn on Earth. We can use this knowledge to make the next generation of spacecraft even safer,” said Dr. Paul Ronney of the University of California in Los Angeles, lead scientist for the Structure of Flame Balls at Low Lewis-number experiment.

Both Payload Specialist Dr. Greg Linteris and Payload Commander Dr. Janice Voss performed runs of the flame ball experiment today. This morning, Linteris performed a run of the experiment using a fuel mixture of 4.6 percent hydrogen in carbon dioxide, the most diluted hydrogen/carbon dioxide mixture to be used. After the third sparking attempt, what resulted were two balls of flame that burned for the 500 second duration of the experiment. Upon a reburn attempt the remaining fuel mixture produced a single flame ball.

“We’re almost getting more data than we know what to do with, and we’re going to be spending a lot of time trying to analyze all of this,” said Ronney.

Today, Mission Specialist Dr. Don Thomas and Payload Specialist Dr. Roger Crouch conducted an experiment that could improve manufacturing processes on Earth. Bubbles that form during the processing of materials can cause many complications in a variety of industrial applications, including the solidification of certain alloys which involve systems where large number bubble and drop dispersions are used.

The Bubble and Drop Nonlinear Dynamics experiment, lead by Dr. L.G. Leal of the University of California at Santa Barbara, will help scientist better understand how bubbles respond to ultrasonic radiation pressure -- possibly leading to a technique that could eliminate or counteract the complications that bubbles cause during materials processing.

During the experiment, bubbles are deployed into a water-filled chamber within the Glovebox. Scientists are assessing their ability to control bubble location, manipulate double bubbles and maximize bubble shape. Shape deformation is being studied as a function of size and ultrasonic pressure. The effect of ultrasonic radiation pressure on bubbles will also be assessed by bringing two single bubbles together to form one.

This afternoon, Linteris initiated an experiment in TEMPUS to investigate the maximum amount that a sample of aluminum-copper-iron and aluminum-copper-cobalt melts could be cooled below its freezing point and remain liquid. The investigation, led by Dr. D.M. Herlach of the German Aerospace Research Establishment in Cologne, Germany, could shed light on nucleation, an important chemical and industrial process.

The gum ball-size sample is covered with a thin layer of gold. “The gold is protecting the sample from oxidation,” explained Herlach. “If the sample -- containing aluminum -- were to oxidize, it could not be undercooled.” As the gold-plated sample is processing, researchers are measuring the specific heat of the melt, an important parameter for modeling nucleation and growth processes, which could improve the analysis of undercooling experiments performed in space as well as on Earth.

Crew members from both shifts performed shear cell rotations of the germanium sample processing in the Large Isothermal Furnace -- with Thomas completing one shortly before noon and Voss performing one rotation around 1:30 p.m. This procedure is part of an experiment to study the diffusion process of tracers, or impurities, in melted germanium, an element widely used as a semiconductor and alloying agent.

During the shear cell rotation, samples of pure germanium and germanium with an impurity are rotated into contact with each other. After an opportunity to mingle together, or diffuse, the resulting single sample is sheared into segments and cooled for post-flight analysis.

“This is the first time diffusion in semiconductors has been studied in space. Diffusion of liquid metals has been studied before, but not semiconductors. The difference is metals expand when melted and semiconductors expand, like water, upon freezing. That subtle difference made the development of technology to conduct this experiment very difficult,” said the study’s principle investigator Dr. David N. Matthiesen of Case Western Reserve University in Cleveland, Ohio.

At the beginning of his shift, Crouch successfully performed an inflight maintenance procedure for the Large Isothermal Furnace. One thermocouple -- an electronic temperature sensor -- in the cartridges used for Matthiesen’s samples was not working. After the procedure, the ground crew began to receive data from the thermocouple again.

This evening, Crouch will continue the bubble experiment and Voss will perform another run of the flame ball experiment using the richest fuel mixture yet to be burned.

The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 10.


- end -

text-only version of this release