Aug 242010
Authors: Emily Johnson

When a spacecraft launches into the atmosphere, there is no guarantee how long it will last.

Cody Farnell and Professor John Williams of the Mechanical Engineering Department are working on a project that could give scientists a little more certainty after they push the launch button.

“Ideally, NASA would be ready for super ambitious missions, like traveling out from the solar system into the stars, which is something that hasn’t been done yet,” said Williams.

A report by Farnell and Williams, published in the Journal of Propulsion and Power, about their experiment, which aims to increase the life expectancy of a grid used in an ion thruster. An ion thruster is the power behind the spacecraft.

“The idea is to increase the life expectancy of the grids, which can be the first component that stops working,” Farnell, a post-doctoral researcher, said. “It would be similar to increasing the life of a car’s transmission, which might fail after a certain number of miles (or hours) of use.”

Farnell used an evolutionary algorithm, which is a mathematical equation, to do that. The algorithm uses ideas from evolution to “mate” good grid sets to form potentially better grid sets. Evolutionary algorithms, also known as genetic algorithms, have been around for a long time and can be applied in many scientific settings.

“Ion thrusters on satellites are usually powered using solar power,” Farnell said. “What I did doesn’t improve its efficiency, it would improve the length of time it would work.”

Professor Williams said that prolonging a grid’s life is a money saver. Launching an object into space takes energy, coming in at about $30,000 per kilogram.

By changing things such as hole sizing and spacing, grid thickness, grid spacing and voltage levels, performance levels of the grid are optimized which can result in spacecraft being able to travel faster and farther.

The next step, Farnell said, would be to physically build and test the grid set in the lab to verify the computer simulation they developed.

“If we can cut out ten kilograms, we save $300 thousand,” Williams said. “Propellant is like fuel, once it’s used, you can’t get ever get it back.”

Staff writer Emily Johnson can be reached at

Cody Farnell

  • Postdoctoral researcher at the Engineering Research Center.
  • Graduated from CSU in 2007.
  • Started a research company with his brother Casey Farnell and Professor John Williams called Plasma Controls.
  • Working on a project at CSU to improve the life of an ion thruster grid.
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