Smooth operators in space
How supercomputers help to overcome the technical challenge of keeping satellites working smoothly hundreds of kilometres above earth.
As a NASA research satellite orbits earth, its sensors, solar panels and cameras twist and turn to track rain and snowfall hundreds of kilometres away. Precision-engineered gears move the large, sensitive equipment in the vacuum of space.
A special lubricant is used on these gears to keep them turning smoothly. It must be able to withstand the extreme conditions of space and keep working for the lifetime of the satellite, which can be up to 50 years.
For the engineers on the ground working on such space technology, developing lubricants like these poses a technical challenge: how to test products on earth which must work in space.
With few laboratories available to run tests in space conditions, one answer lies in the use of new software in supercomputers that can simulate chemical products, without touching a test tube or a Petri dish. This approach is known as computational chemistry.
“It isn’t simply the software that is special, it’s also the ability to test the theories of scientists and engineers,” says Rajappan Vetrivel, head of computational chemistry at Shell. “We can make discoveries that are impossible in a physical laboratory – discoveries that could help solve some of mankind’s biggest challenges.”
Supercomputers allow scientists to build chains of molecules on a screen and make assessments of how products will perform.
A computer model of iso-octane, a key molecule used in gasoline, after reacting with oxygen
One of the toughest questions for the team that designed the lubricant for satellites was whether it could withstand the extreme temperature variations of space. On the NASA research satellite, the lubricant needs to endure highs of 150°C and lows of -150°C. The temperature varies as the satellite circles earth and moves nearer to the sun, or further away. If the lubricant evaporates or freezes, the satellite’s functions will fail.
High-performance computers are needed for these simulations.
“On a supercomputer many of the equations and calculations can be done in parallel, meaning a simulation only takes about a week,” says Kunj Tandon, a computational chemist with Shell in Bangalore, India. “Computer power has advanced so much that now we can recreate most environments digitally.” The same set of calculations might take a normal laptop 30 years.
Supercomputers are particularly helpful when studying particles too small to monitor in physical experiments. Scientists can zoom in on individual molecules and look at different atomic arrangements. Based on what they find, they can change molecular properties, making the lubricant better able to withstand colder temperatures.
“Computational chemists play increasingly central roles in research and development in many fields,” says Dewi Lewis, Professor of Computational Chemistry at University College London.
For now, supercomputers in chemistry remain an emerging technology. Yet the future possibilities, like space, are vast.
Story by Sarah Kempe
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