University of Arizona researchers eagerly await the arrival of a small cylinder of aluminum silicon alloy that was melted and resolidified in the zero gravity of a metals lab on the International Space Station.
They plan to "slice it like a bologna and examine it from one end to the other," said David Poirier, a UA professor of materials science and engineering.
Poirier and his team expect to see a more perfect version of the alloy than can be created on Earth.
The ingot, a product of the first of two tests being performed on the same alloy, already has been picked up by the crew of space shuttle Endeavour, which has a scheduled landing Sunday in Florida. Another ingot awaits testing next month.
The scientists know that gravity interferes with the formation of perfect crystals when molten alloys flow into casts.
In space, the metal should re-form along symmetrical axes, creating a structure with fewer flaws and greater strength, Poirier said.
"We all know that hot air rises," said Robert Erdmann, Poirier's partner in the experiment.
"Hot, liquid metal also rises. In space, there is no way to distinguish between up and down. It doesn't want to move in any particular direction," said Erdmann, an assistant professor of materials science and engineering.
The experiment was controlled from Earth and performed while the space station astronauts slept to avoid any acceleration caused by their movement, Erdmann said.
He and graduate student Matthew Goodman went to NASA's Marshall Space Flight Center in Huntsville, Ala., earlier this month to supervise, armed with calculations and computer programs drawn from an Earth-based mirror of the experiment done by their research partner, Surendra Tewari of Cleveland State University.
Tewari also will perform the slicing and analysis of the sample.
Erdmann and Goodman waited as instruments took repeated temperature readings at 12 points on the furnace and relayed the result to the German headquarters of the European Space Agency. The information was then relayed to Huntsville, where the pair compared it with their computerized data and made adjustments in the furnace temperature.
That part took three to four hours, or more than 10,000 seconds, which is the reference used by Goodman's computer programs.
"We only got one shot to run this experiment 100 percent right," Goodman said. "It was stressful, but very fun."
Joining Poirier and Erdmann in their experiment was a once-in-a-lifetime opportunity, Goodman said, but "not as interesting as it sounds. It was basically me staring at a computer screen for two years."
Goodman said he was interested in model rocketry as a kid and wanted to be an astronaut - until he computed the odds of that happening. He's been melting metals since his days at Catalina Foothills High School, when he built a forge and foundry from scrap metal in his parents' yard.
He'll finish his master's in materials science and engineering this year, and then it's off to graduate school, this time with a biomedical focus. He has heard from a couple of programs that want him and is waiting to hear from Harvard and MIT.
Goodman's translation of his math into complex computer programs was critical to the success of the experiment, Erdmann said.
The ultimate goal of the experiment, Erdmann said, isn't to produce some new space-age metal, but to discover how the casting process affects the product.
"Understanding the connection between processing and structure, this is a very fundamental link," Erdmann said.
The researchers won't even get a chance to test the material's properties, Poirier said. The cylinder, about 6 inches long and one-quarter inch in diameter, will be destroyed in the process of slicing it and mapping its microstructure.
Poirier doesn't expect foundries to be operating in space any time soon, but thinks scientists will find his results useful on Earth.
"There are so many clever people, especially among the engineering community, who might figure out how to mitigate the movement of the liquid as the alloy solidifies," he said.
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