SPACE agencies may one day have Charles Darwin to thank for the longevity of their spacecraft. The life expectancy of a popular type of ion engine has been almost doubled using 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 …