Initially, the mission went to plan: the rocket launched OK (incidentally, the first successful American resupply launch since that other rocket went boom), the cargo part separated from the main rocket first stage, and is now on its way to the ISS, where it should arrive on Monday.
The first stage made it to the 'autonomous spaceport drone' (that's a robot barge to you and me) without problem, but then, according to SpaceX founder Elon Musk, "landed hard":
But as Musk points out, the mission wasn't a complete failure. Landing a rocket vertically on a moving ship isn't exactly easy — SpaceX has likened it to "trying to balance a rubber broomstick on your hand in the middle of a wind storm". The actual landing is comprised of a few different parts: First, a boostback burn gets the craft headed in the right direction; a second 'supersonic retro propulsion' slows the rocket to 250 meters per second; and a final landing burn brings it to about 2 meters per second.
From the sounds of things, the first two parts went well: the rocket certainly hit its target, and presumably didn't do so at several thousand miles per hour. Two outta three ain't bad. [Twitter]