Dynamics of Bumping
in the
Night
Diego Troya | Virginia Tech
On the first day of classes at Virginia Tech, Diego Troya’s main
focus was giving a good first lecture in freshman chemistry, but he had
one eye on the sky above the duck pond that is framed by the window of
his lab. He was, like many, following the news of the space shuttle Endeavour.
During its journey, it lost a bit of its foam surface, causing a gouge.
There was concern about its landing, which turned out to be quite safe.
In his lab, Troya studies molecular simulations to study the degradation of the polymers that coat and protect spacecraft and satellites like the Hubble telescope and the International Space Station. His studies will add to knowledge of how the skin of a spacecraft — often Teflon — interacts with its environment, and how the gases around Mars or Venus interact with whatever humans send their way. He plans to look closely, very closely, atom by atom.
Simulation of mechanical properties of Carbon Nanotubes (CNTs) and CNT-based nanocomposites using quantum mechanics.
If things fall apart in orbit way out in space, Troya may be curious about just which gas atoms were interacting with which polymer atoms, and how and why.
“The goal is to understand how things occur at an atomic level. If we know that we can control those reactions,” he said. It’s called reaction dynamics. Some reactions are harmful, like corrosion, and some are helpful, like the delivery of a gas that needs to be deposited on that surface. In any case, “If we understand dynamics of a reaction, we control it, accelerate it, stop it.”
What makes Troya’s work so vital to space programs is what happens when a vehicle is launched into orbit. You have to pay a lot for the fuel, and thus want to avoid any extra weight. That’s why satellites use a polymer, something very strong yet light.
But the polymer skin degrades in space, especially at a low-Earth altitude, say 200 kilometers, where conditions are extremely oxidizing. Temperatures swing dramatically, in what’s known as thermal cycling, as the spacecraft faces toward the Sun or away from it. Many of the interactions of polymer skins and their environment can pose threats to a multimillion-dollar satellite project.
Diego Troya welcomes big problems with lots at stake. When he first set out from home in the La Rioja wine region of Spain in 1999, he was a young chemist leaving behind the family vineyards to pursue one immense question. “I knew I wanted to learn how to study the dynamics of large chemical reactions,” he says. “We can easily understand small reactions, say, with three atoms. But for those with 3,000 atoms, it’s very hard to study.” He had won a fellowship for graduate work in chemistry from the Spanish Ministry of Education and Culture that let him travel anywhere, for three months a year during four years of study. His first destination was Evanston, Ill., and the lab of George C. Schatz, an eminent theorist at Northwestern. Troya wound up joining the Schatz team and staying until he moved to Virginia Tech in 2004.
His study of the interface at the atomic level of a polymer surface and gases is something no one has ever done, even though the phenomenon occurs everywhere.
Take the skin as a polymer, for example. It is bombarded with atoms of oxygen, nitrogen, argon and the rest of what we call air. No harm done. But try to picture one molecule at a time heading for that piece of skin, bouncing, ricocheting, and you get a picture of his research. Apply it to the Endeavour and you see one of its main applications.
“What if a satellite is supposed to last for 20 years, and it cracks after 10 years and dies? What this means,” he said, “is that the study of these surfaces is an unsolved problem.” For now.
Nov. 1, 2007
