WASHINGTON, April 18 (Xinhua) -- A commercial spacecraft operated by U.S. space company SpaceX blasted off Friday for its third cargo resupply mission to the International Space Station ( ISS), NASA TV showed.
The unmanned Dragon spacecraft was launched aboard a Falcon 9 rocket at 3:25 p.m. EDT (1925 GMT) from the Cape Canaveral Air Force Station in Florida.
"Liftoff!" NASA said in its launch blog. "Dragon is on the way to the International Space Station!"
The spacecraft carried nearly 5,000 pounds (about 2,268 kilograms) of supplies and payloads, including materials to support more than 150 scientific experiments this year.
SpaceX said it will also use the launch to test the recovery of Falcon 9's first stage and gave the chance of success at just 30 to 40 percent.
According to the California-based company, soon after the first stage shut down and separated from the upper stage, it was expected to relight some of its engines for a braking maneuver. Then, the stage ignited an engine again just above the Atlantic Ocean for a landing burn.
"Falcon 9 is carrying four landing legs, which will deploy partway into the landing burn. Eventually, SpaceX hopes to land the first stage on land," the company said.
"Though success is unlikely with this test, it represents an exciting effort toward someday developing a reusable rocket."
At a post-launch press conference, SpaceX CEO Elon Musk said that he "wouldn't give it high odds" for successful landing due to the rough seas and experimental nature of the test.
However, he said he considered it "a success" that the first stage had a zero roll rate. He also said he's confident they will "have a decent change of bringing a stage back this year."
If everything goes as planned, Dragon will arrive at the station Sunday, when it will be grappled and berthed to the orbiting lab for an expected four-week visit. It is scheduled to depart the space station May 18 for a parachute-assisted splashdown off the coast of California.
The launch is proceeding despite the failure last Friday of a backup computer called multiplexer-demultiplexer (MDM) that provides commands to some space station systems, including the external cooling system and the Mobile Transporter rail car on the S0 truss of the station.
This is the third of at least 12 missions to the space station that SpaceX will fly for U.S. space agency NASA under a 1.6- billion-U.S.dollar Commercial Resupply Services contract.
Besides SpaceX, NASA has also signed a deal with another private company called Orbital Sciences Corp. to supply cargo to the space station.