SpaceX launches unmanned rocket

An unmanned SpaceX rocket blasted off from Florida on Tuesday to send a cargo ship to the International Space Station, then flipped around and made a hard landing on a platform in the ocean.

The booster's flyback, years in the making, marks another step in the company's quest to develop rockets that can be refurbished and reflown, potentially slashing launch costs.

"This might change completely how we approach transportation to space," SpaceX vice-president Hans Koenigsman told reporters during a prelaunch press conference.

• SpaceXFalcon 9 launch ignites dream of reusable rocket

The 63-metre (208-foottall) Falcon 9 rocket, carrying a Dragon capsule, thundered off its seaside launch pad at Cape Canaveral Air Force Station at 4:10 p.m. ET. A launch attempt on Monday was delayed by poor weather.

After sending the capsule on its way to orbit, the rocket's first stage flipped around, fired engines to guide its descent, deployed steering fins and landing legs and touched down on a customized barge stationed about 322 kilometresoff the coast of Jacksonville, Fla.

"Ascent successful. Dragon enroute to Space Station. Rocket landed on droneship, but too hard for survival,"SpaceX founder and chief executive Elon Musk said on Twitter.

During a previous landing attempt in January, the rocket ran out of hydraulic fluid for its steering fins, causing it to crash into the platform.

A second attempt in February was called off because of high seas, but the rocket successfully ran through its pre-programmed landing sequence and hovered vertically above the waves before splashing down and breaking apart.

The primary purpose of Tuesday's launch was to deliverfood, clothing, equipment including an Italian-made espresso machine and science experiments to the station, a $100-billion research laboratory about 418 kilometresabove Earth.

SpaceX is one of two companies hired by NASA to fly cargo to the station following the retirement of the space shuttles. In addition to a recently extended 15-flight NASA cargo delivery contract, worth more than $2 billion, SpaceX is working on a passenger version of the Dragon capsule and has dozens of contracts to deliver commercial communications satellites into orbit.

It hopes to be certified to fly U.S. military payloads by June.