“Rapid unplanned disassembly” is how Elon Musk, the boss of SpaceX, a rocket company, jokingly refers to failures that cause rockets to explode. Alas, there have been several examples lately, including the loss of one of SpaceX’s unmanned Falcon 9 craft last Sunday, shortly after lift-off on a cargo mission to the International Space Station. That followed the explosion in October of a resupply rocket built by Orbital Sciences, another private firm, and the loss of a Russian cargo capsule in April, which went into the wrong orbit and burned up. Despite these three failures, astronauts on the ISS had enough supplies to last until October. But there were more crossed fingers than usual when a Russian cargo mission lifted off from Baikonur in Kazakhstan today at 4.55am, GMT. The successful launch put an end to a run of bad luck. But space flight remains a precarious business.