Dragon, which arrived Friday as part of a test flight, was the first privately owned spaceship to reach the $100 billion orbital outpost, a 15-nation project. It was scheduled to splash down in the Pacific Ocean about 560 miles southwest of Los Angeles at 11:44 a.m. EDT.

The United States has been without its own transportation to the space station since its space shuttles were retired last year, leaving Russian Soyuz spacecraft, which are used mainly to transport crew and have little room for cargo, as the only vehicles now flying to the station that return to Earth.

Rather than build and operate a government-owned replacement, NASA is investing in companies such as Space Exploration Technologies, or SpaceX, with the aim of buying rides for its cargo - and eventually astronauts - on commercial vehicles, a far cheaper alternative.

The successful trial run is expected to clear SpaceX to begin working off its 12-flight, $1.6 billion NASA contract to fly cargo to the station.

A second commercial freighter, built by Orbital Sciences Corp is expected to debut this year.

"Our plans are to carry out a test launch in the August-September time frame and the demonstration mission - same as what SpaceX impressively just did - in the November-December time frame," Orbital spokesman Barry Beneski wrote in an email to Reuters.

Orbital has a similar contract to deliver space station cargo, valued at $1.9 billion.

RELEASE THE DRAGON

In Thursday's operation, astronauts detached the Dragon capsule from its berthing port at 4:07 a.m. EDT (0807 GMT) using the station's 58-foot long (17.7-meter) robotic crane, and released it at 5:49 a.m. EDT (0949 GMT) as the spacecraft soared 250 miles above the planet.

"It's been an extremely successful joint mission," said NASA mission commentator Josh Byerly.

SpaceX successful recovered a Dragon capsule from orbit during a previous test flight in December 2010.

"We've done it once, but it's still a very challenging phase of flight," SpaceX mission director John Couluris told reporters on Wednesday.

"The ability to get to (the) space station on our first time, to not only rendezvous but then to berth, transfer cargo and depart safely are major mission objectives. We would call that mission alone a success," Couluris said.

After leaving the space station, the Dragon capsule fired its steering jets to leave orbit and head back toward Earth. Recovery ships owned by American Marine Corp of Los Angeles were standing by to pick up the capsule and bring it back to the Port of Los Angeles, a trip that should take two or three days.

From there, Dragon will be taken to a SpaceX processing facility in McGregor, Texas, unloaded and inspected.

The company's last test will be to see if it can speedily return some equipment from the station to NASA within 48 hours, a practice run for ferrying home precious scientific samples when Dragon begins regular cargo hauls.

The rest of the 1,300 lbs (590 kg) of gear returning on Dragon is due to be sent to NASA within two weeks, said flight director Holly Ridings.

"Because this is a test flight, specifically the program made sure that there's not anything coming home that we couldn't afford to not get back," she said.

"I know it's a really important capability to prove for NASA and for the space station program as we go forward, since this vehicle has the unique capability to return cargo," Ridings said.

(Editing by Tim Pearce)

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