Stars in their eyes

IN A clean room at the Airbus Defence & Space (ADS) factory north of London, scientists are working on LISA Pathfinder (pictured), a hexagon-shaped satellite due to be launched next year. The aim of the ambitious space mission is to try, for the first time, to find and measure gravitational waves—ripples in space-time predicted by Einstein’s general theory of relativity. If that’s possible, earthlings would have further evidence that the theory is true, and they should also, eventually, be able to locate black holes more accurately.

To do all that, however, LISA first has to get to a “Lagrange point”, a place where spacecraft can float stably while getting no farther from the earth. This is essential for detecting the gravitational waves. The only force that could then ruffle LISA would be solar wind, explains Justin Byrne, a deputy director of ADS. Solar wind is so light, however, that developing thrusters soft and accurate enough to counteract it has been “the trickiest bit of all”. It would take 1,000 of the thrusters developed for LISA to lift a single piece of paper; LISA has just four.