Rockets have to carry all the fuel they need not only to lift their payload, but to carry the unburned remainder of the fuel itself, an expensive business which rapidly leads to diminishing returns. So a craft that doesn’t have to take its fuel with it is a dream of rocket scientists. New Scientist magazine has recently reported on US experiments with a launch vehicle that rides into space on a beam of laser light. It uses infra-red lasers left over from the old Star Wars experiments of the eighties to fire a series of extremely short and powerful bursts of light focused on the rocket. A carefully-shaped cavity concentrates the light into a tiny area where it is so intense it rips air molecules apart to form a hot plasma that shoots out at speed, driving the craft upwards. Above the atmosphere, the lightcraft will obviously have to carry its own supply of gas to replace the air, but even so great economies in weight and cost of getting satellites into orbit may be possible.