Liftoff of the company's Falcon 9 rocket and Dragon capsule is scheduled for 8:35 p.m. EDT on Sunday (0035 GMT Monday) from Cape Canaveral Air Force Station in Florida.

If successful, the company, founded and run by Internet entrepreneur Elon Musk, will restore a U.S. supply line to the station that was cut off by the retirement of the space shuttles last year.

Since then, NASA has been dependent on Russian, European and Japanese freighters to service the station, a permanently staffed research laboratory that flies about 250 miles above Earth.

In May the firm, also known as SpaceX, made a practice run to the $100 billion orbital outpost, a project of 15 countries, clearing the way for the first of 12 cargo runs.

SpaceX is one of two firms hired by NASA to deliver cargo to the station.

Its other contractor, Orbital Sciences Corp., on October 1 rolled out its first Antares rocket to a new launch pad on Wallops Island, Virginia, for an engine test-firing slated for this month or early November.

The rocket is scheduled to make its debut flight before the end of the year.

Orbital also plans a practice run to the space station, similar to what SpaceX did when its Dragon ship docked at the station. If all goes well, Orbital will be cleared to begin work on its $1.9-billion NASA contract to fly cargo to the station.

REUSABLE

For Dragon's first supply run, NASA is sending about 1,000 pounds (454 kg) of food, clothing, supplies and science gear to the station.

Unlike previous station cargo ships, which were not reusable and burned up in the atmosphere during descent, SpaceX's capsule returns to Earth.

As a result, it will be able to carry back experiment samples and station hardware that is broken or no longer needed.

NASA contributed $396 million to SpaceX and up to $288 million to Orbital to help the firms develop their cargo ships. The agency is running a related, $1.12 billion program with SpaceX, Boeing and privately owned Sierra Nevada Corp. to design station crew transports.

"There's this burst of creativity going on in the private sector," said former NASA astronaut Garrett Reisman, who joined SpaceX in March 2011.

"It's analogous to the golden age of air travel, between the two world wars, where people were trying all different things because nobody knew back then what an airplane was supposed to look like," he said at the American Institute of Aeronautics and Astronautics space conference last month.

NASA hopes to be able to buy rides for its astronauts on commercial space taxis by 2017, breaking Russia's monopoly on station crew transports.

The Dragon capsule was expected to reach the station on Wednesday. It would then remain berthed at the outpost for about 18 days and make a parachute descent into the Pacific Ocean on October 28.

(Edited by David Adams and Xavier Briand)

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