Darwin-inspired spacecraft engine with double life expectancy created

Inspired by Charles Darwin, scientists have doubled the life expectancy of a popular type of ion engine Movie Camera using a software that mimics the way natural selection evolves ever-fitter designs.

Electrostatic ion engines are becoming popular in space missions.

Instead of relying on burning large amounts of heavy liquid propellant for thrust, they use solar power to ionise a small supply of xenon gas.

A high voltage applied across a pair of gridded electrodes sends the positively charged ions rushing at high speed towards the negative electrode.

Most ions pass through the grid, generating thrust.

However, some ions collide with the grid itself, causing it to gradually wear out, said Cody Farnell, a space flight engineer at the University of Colorado in Fort Collins.

Simulations suggest grids in a typical NASA engine will last 2.8 years - but Farnell wondered if changing the grid's design could extend its lifespan, reports New Scientist.

He used evolution-mimicking software called a genetic algorithm (GA), and started by instructing the algorithm to randomly generate values corresponding to the geometry of the grid and the voltages applied to it.

These values can be thought of as analogous to genes.

Each combination of values was then fed into a simulator to give an idea of the grid's performance and its expected lifetime.

If the performance was promising, the "genetic material" was subjected to further random changes, or mutation, and this process was repeated until no more improvements were forthcoming.

After 100 generations, the GA spawned a geometry/voltage set that boosted the ion engine grid's lifetime to 5.1 years - at least in the simulator

Factors optimised included grid hole diameter, hole spacing and the thickness of the grids.

The engine could be improved further by evolving the other parts too, said Farnell.

After 100 generations, the algorithm spawned a design that almost doubled engine lifetime

Propulsion engineer Steven Gabriel at the University of Southampton in the UK is developing a triple-gridded ion engine.

He said Farnell's work could have major implications if real-world tests of his design match the simulations.

The study has been published in the Journal of Propulsion and Power.