CAPE CANAVERAL, Fla. — SpaceX launched its 21st rocket of the year today (Aug 29), sending a robotic Dragon cargo capsule toward the International Space Station (ISS) before nailing a landing at sea.

A two-stage Falcon 9 rocket blasted off from Launch Complex 39A here at NASA's Kennedy Space Center at 3:14 a.m. EDT (0714 GMT), kicking off the company's 23rd cargo resupply mission to the orbiting lab for NASA. The Dragon is packed with more than 4,800 pounds (2,200 kilograms) of supplies, scientific experiments and hardware, including a new robotic arm that will be tested inside the space station's Bishop Airlock.

A little less than eight minutes after liftoff, the Falcon 9's first stage returned to Earth, landing on one of SpaceX's drone ships in the Atlantic Ocean in a smooth touchdown. The massive ship, called "A Shortfall of Gravitas," is the newest of three drone ships in the company's fleet of recovery vessels that catch falling boosters and return them to port for later reuse.