The largest and most powerful rocket ever built has blasted off from Texas but blew up within minutes in a test flight that its makers, SpaceX, hope will be the first step on a human journey to Mars. It appeared that the two sections of the rocket system – the booster and cruise vessel – were unable to separate properly after takeoff, possibly causing the spacecraft to fail. SpaceX had previously cautioned that the chances of success were low and that the aim of the test flight was to gather data, regardless of whether the full mission was achieved.