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Checking Out Long-Term Performance Of Space Materials

The University of Chicago will become headquarters for a new national center devoted to investigating the long-term performance of high-tech materials in space with a $5 million grant from the U.S. Department of Defense.

The center's unclassified fundamental research program could potentially lead to the development of new and improved materials for satellites, space stations, high-altitude aircraft, as well as advanced terrestrial applications.

"We're trying to understand how all sorts of materials are going to perform in a very aggressive chemical environment," said project leader Steven Sibener, Professor of Chemistry and Director of the Materials Research Science and Engineering Center at the University of Chicago.

"Right now, the actual atomic-level details by which high-performance materials react, erode, and ultimately age when subjected to the harsh chemical environment of low-earth orbit are very poorly understood. This is a superb opportunity to explore materials chemistry in an extreme environment."

The grant is part of the Multidisciplinary University Research Initiative, a program designed to address large and complex science and engineering problems that have potential for future Department of Defense and civilian applications.

The Chicago-led center survived a funding competition that began with 416 proposals, 48 of which resulted in grants. Five years of funding will began May 1 for the new effort, which is called the Center for Materials Chemistry in the Space Environment.

Collaborating with Sibener are Luping Yu, Professor in Chemistry; John Tully, Yale University; George Schatz, Northwestern University; Dennis Jacobs, University of Notre Dame; Barbara Garrison, Pennsylvania State University; and Timothy Minton, Montana State University. Other collaborators will come from the National Aeronautics and Space Administration, U.S. Air Force Research Laboratories and Boeing.

The collaboration will initially focus its attention on understanding the chemistry of polymers in space. Polymers, a class of relatively soft, lightweight materials that includes Teflon and Kapton, are widely used in spacecraft design. Hard coatings such as diamond films also will be examined.

"The current materials being used in space are still what I would call first-generation space materials that just happen to work at some level," Sibener said. "We intend to go beyond such fortuitous situations and actually develop improved new materials using molecular-level understanding of the relevant chemistry to achieve intentionally designed performance advantages. Recent advances in materials experimentation, chemical synthesis and theory make this the right time to tackle this challenging problem."

Many people think that the orbital environment in space is benign because outer space is perceived to be empty and quiet, Sibener said. In fact, it is a hotbed of corrosive forces capable of eradicating a wide variety of materials.

The space environment is bathed continuously in highly energetic and destructive ultraviolet radiation from the sun, for example. Equally destructive swarms of electrons, electrically charged particles, and oxygen atoms also permeate the orbital environment, depending on the altitude, time of day and cycle of solar activity.

Much of what is known about the effects of such phenomena on materials resulted from the study of the Long Duration Exposure Facility. Launched in 1984 by the space shuttle Challenger, LDEF was mounted with a variety of metals, polymers and ceramics to see how they would fare in the extreme space environment.

The satellite completed more than 32,000 Earth orbits at altitudes ranging from 275 to 175 miles before the shuttle Columbia returned it to Earth in 1990.

LDEF demonstrated how little scientists knew about the durability of materials in space. Some samples that experts thought would survive disappeared, while others that were expected to be destroyed managed to endure. "It tells us that we do not yet really have a good predictive understanding of the underlying chemistry that determines how many of these materials age in space," Sibener said.

The synergistic effects of space chemistry complicate the issue. It's one thing to understand what happens when electrons, ions, oxygen atoms or ultraviolet radiation separately react with a material and quite another matter to understand the reactions when any two or three of the phenomena operate at the same time.

Orbital debris-both man-made and meteoritic-takes its toll, too, as LDEF also showed. One question Sibener and his colleagues hope to answer is how the microscopic defects left by debris impacts influence the subsequent chemistry and structural evolution of such materials.

A synthetic chemist, Yu will produce experimental polymer materials for the collaboration similar to those used in space. Then Yu, along with Sibener, Minton and Jacobs, will conduct laboratory experiments on the materials with gas-surface scattering instruments and powerful microscopes capable of monitoring material structure at the atomic level.

Theoreticians Garrison, Schatz and Tully, meanwhile, will perform calculations to learn how various chemical reactions would be expected to affect the new materials. The combined experimental and theoretical insights will provide guidance to Yu's critical synthetic effort to ultimately design improved compounds for space applications.

The team is eager to tackle the center's work. "There are not only some technological issues, but some fundamental science that you have to address," Yu said. "That's why I'm very excited about this."

Especially appealing to Yu is the challenge presented by trying to synthesize a polymer that resists multiple sources of corrosion in space. In theory, a polymer coated with aluminum or some other metal could possibly resist the corrosion. When a marauding oxygen atom strikes the material, the atom and the metal will react to form a surface film of aluminum oxide that prevents further corrosion. At the same time, the aluminum oxide would serve as a good conductor, potentially draining away damaging floods of electrons.

Even if the new center falls short of synthesizing a new high-performance material for space, "the fundamental science from this collaboration will be very interesting," Yu said. - By Steven N. Koppes

[Contact: Steve Koppes]

08-May-2001

 

 

 

 

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