Colorado State University Student Creates Formula that Could Improve Spacecraft Thrusters

Note to Reporters: A photo of John Williams is available with the news release at

A postdoctoral researcher at Colorado State University has created a computer simulation that could lead to a doubling of the time that spacecraft and satellites are propelled in space.

The simulation, developed by Cody Farnell, a researcher working with Professor John Williams in the Department of Mechanical Engineering, improves the performance of an ion thruster’s grids, which are used to accelerate ions to high speed to give the spacecraft thrust.

An ion thruster, a type of electric propulsion, converts electrical energy, rather than chemical energy, into thrust for spacecraft propulsion. That high-efficiency thrust keeps satellites and spacecraft floating above Earth for long periods of time to accomplish their missions. Highly efficient ion thrusters are used commercially to keep satellites in proper orbit around Earth and by space agencies to propel spacecraft on deep space missions.

Farnell and Williams published a paper on the simulation earlier this year in the Journal of Propulsion and Power.

Ion propulsion uses electric power instead of chemical fuel as a thrust mechanism. How it works: Solar panels on the spacecraft convert the sun’s energy into electrical power. That power is transferred to a cathode which heats up and releases electrons that are energized and allowed to interact with a gas such as xenon, changing the atoms into ions. These ions are then expelled from the thruster through electrically charged “grids,” which results in thrust.

The ion thruster’s grids may be the first component to wear out, causing the thruster to stop working. Farnell’s simulation uses an evolutionary algorithm to control the grid variables – such as the size of the holes in the grid – to minimize erosion.

The simulation borrows evolutionary ideas to help design optimized grids by changing things like geometries (hole size, hole spacing, grid thickness, grid spacing) and voltages, said Farnell. “We plan further studies in these areas. The next step would be to test the optimized design experimentally in the laboratory,” he said.

Farnell and his twin brother, Casey, are both postdoctoral researchers working with Williams. Williams directs the Colorado State University Electric Propulsion & Plasma Engineering (CEPPE) Laboratory, which has provided research, development and testing of plasma sources and diagnostics since 1965.