A mission by an unmanned SpaceX Falcon-9 rocket has ended in failure after it exploded after lift-off from Cape Canaveral, Florida. br br The rocket was supposed to despatch a cargo ship to the International Space Station (ISS). br br The lower segment of the rocket was then meant to turn around and use its engines to bring itself down to a floating barge. br br It was US company SpaceX's third failed attempt at the manoeuvre.