SpaceX Dragon prepares to leave space station

US company SpaceX's Dragon cargo ship is preparing to make its return journey to Earth after a landmark mission to the International Space Station, NASA and SpaceX representatives said Wednesday. The release of the unmanned Dragon is set for 5:35 am Eastern time (0935 GMT) on Friday, with an intact splashdown in the Pacific Ocean off California planned for 1444 GMT, NASA said. "We have a lot ahead of us on the SpaceX side," said mission director John Couluris in a briefing with reporters on the eve of the spacecraft's return after a seven-day mission to the orbiting outpost. "We have done it once," he said, referring to the Dragon's test flight in December 2010 when the capsule entered and returned safely from orbit for the first time. "But it is still a very challenging phase of flight," he added. "We are not taking this lightly at all." The capsule is supposed to make an ocean landing 490 nautical miles (907 kilometers) southwest of Los Angeles, where three vessels are standing by as recovery boats. It will then be transported to Texas so that the cargo it is bringing back can be returned to NASA, though the US space agency cautioned that if anything goes wrong, there is nothing irreplaceable on board. "There is not anything coming home that we couldn't afford to not get back," said Holly Ridings, NASA flight director. The cargo ship carried 521 kilograms (1,148 pounds) of gear for the space lab, including food, supplies, computers, utilities and science experiments. It plans to return a 660-kilogram load to Earth. On May 25, the Dragon became the first privately owned spacecraft to berth with the ISS, an event that NASA and White House officials hailed as the start of a new era in spaceflight in which commercial enterprise will take a larger role. The United States retired its space shuttle fleet last year, leaving cargo missions up to the space agencies of Russia, Japan and Europe. Until private US ventures come up with a replacement vehicle that can carry humans to the $100 billion orbiting lab, the world's astronauts must rely on Russia's Soyuz capsules at $63 million a ticket.