The unmanned SpaceX Falcon 9 rocket sits on the launch pad at Cape Canaveral Air Force Station
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LIVE: SpaceX rocket launch in Florida

SpaceX is launching an unmanned cargo mission to resupply the International Space Station, and will attempt to soft-land part of the rocket at sea on a floating barge.

Normally the spent stages are destroyed as they fall back to Earth, but the American firm hopes to retrieve part of its Falcon rocket by landing it on the floating platform off the coast of Florida.

If successful, it could lead to less expensive space launches.

The previous attempt was aborted due to a problem with a steering thruster system.