Modeling Plasma Propulsion

New Research Illuminates Complex Processes Inside Plasma Propulsion Systems for Satellites
By Raphael Rosen

Princeton, New Jersey -- September 11, 2018 -- If you think plasma thrusters are found only in science fiction, think again. Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have been uncovering the physics behind these high-tech engines, which maneuver satellites in space. New research involving computer simulations gives physicists confidence that they can peer into the inner workings of these machines.

The research began with an Air Force Office of Scientific Research award to PPPL to investigate the origin of spoke-like plasma structures that appear in Hall thrusters, propulsion devices used to correct the orbits of satellites circling Earth.

Former PPPL physicist Johan Carlsson, working with Princeton University graduate student Andrew Powis and other colleagues, simulated a Penning discharge device — a machine that is simpler and easier to model than a plasma thruster. The simulations, performed on WestGrid, a high-powered computer network in western Canada, and the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility at Lawrence Berkeley National Laboratory, accurately reproduced the spokes observed earlier in experiments conducted by PPPL principal research physicist Yevgeny Raitses with the help of students. Since the Penning device shares many characteristics with plasma thrusters, conclusions based on the Penning discharge model can be applied in general to those thrusters, the researchers say.

“We now have confidence that we have the right ingredients built into our model to reproduce the physics of plasma propulsion devices,” said Carlsson, the lead author of a paper reporting the results in Physics of Plasmas.

Developing the model was a complex process. “It was challenging to build a code that could simulate such a large system in a reasonable time frame,” Powis said. “We ran months of simulations to properly characterize the behavior of the spokes and compare our results to theory and experiments.”

The findings gave assurance of scientific understanding. “The good thing is that we have confidence now that we have all the necessary ingredients to understand spoke formation, which occurs in many types of plasma machines,” Carlsson, now with a private company, said. “This paper shows that three components of fundamental research — experimental study, theoretical calculations, and advanced computation — can help increase the understanding of complex phenomena like spokes.”

Some of the simulations were done at the Princeton Institute for Computational Science and Engineering (PICSciE) and the Princeton Office of Information Technology’s High Performance Computing Center and Visualization Laboratory. The research team included physicists Raitses and Igor Kaganovich from PPPL, Powis from Princeton University, and Ivan Romadanov and Andrei Smolyakov from the University of Saskatchewan. Funding was provided by the Air Force Office of Scientific Research, with simulations enabled by support from WestGrid and Compute Canada.

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy.

 https://www.pppl.gov/news/press-releases/2018/09/engage-engines-new-research-illuminates-complex-processes-inside-plasma