The Dragon cargo ship was carrying 4,000 pounds (1,800 kilograms) of gear to the space station, including a large parking space, known as an International Docking Adaptor, designed to make it easier for an array of commercial crew spacecraft to dock at the orbiting lab in the future.Countdown was normal and the weather was clear, posing no concerns ahead of the launch. After liftoff, SpaceX had planned to make a third try at a controlled, upright landing of its Falcon 9 rocket on an ocean platform with the goal of one day making rockets as reusable as airplanes.