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A commercial vessel carrying a ton of supplies for the International Space Station ran into thruster trouble shortly after liftoff Friday and will miss its docking date, despite a day spent scrambling by flight controllers to fix the problem.

In a press conference Friday afternoon, SpaceX founder Elon Musk said the company had resolved issues that prevented three of the four sets of thrusters on the company's unmanned Dragon capsule from kicking in, delaying the release of solar panels -- and ultimately preventing the vehicle from making its planned docking date.

Dragon's twin solar wings swung opened two hours later than planned as SpaceX worked to bring up the idled thrusters, which Musk said should happen shortly.

“We’ve been deeply engaged in trying to find out what went wrong with the Dragon thruster system,” Musk said over the phone from SpaceX mission control in California. "I’m optimistic that we’ll be able to turn all four thruster pods on and restore full control” soon, he added.

The Dragon is equipped with 18 thrusters, divided into four sets, and can maneuver adequately even with some unavailable. The thruster issues caused SpaceX to miss its scheduled rendezvous.

“Fortunately, we have quite a bit of flexibility in our birthing date,” explained Michael Suffredini, International Space Station program manager. Musk noted that the capsule could orbit safely for up to a month before docking, if needed. And because the cargo is largely scientific, a delay won't put the station crew in any jeopardy.

The problem cropped up following Dragon's separation from the rocket upper stage, nine minutes into the flight. The liftoff was right on time and appeared to go flawlessly; the previous Falcon launch in October suffered a single engine failure that resulted in the loss of a communications satellite that was hitching a ride on the rocket.

This is the first major trouble to strike a Dragon in orbit. Two similar capsules, launched last year, had no problem getting to the orbiting lab.

“It was a little frightening there,” Musk admitted, stressing that the Falcon rocket performed perfectly despite the minor troubles with the Dragon capsule. More than 1 ton of space station supplies are aboard the cargo craft, including some much-needed equipment for air purifiers.

SpaceX has a $1.6 billion contract with NASA for 12 deliveries to restock the space station, and hopes the venture will lead to transporting astronauts there in a few years. A company-sponsored demo mission kicked everything off last May.

Launch controllers applauded and gave high-fives to one another, once the spacecraft safely reached orbit. The successful separation of the Dragon from the rocket was broadcast live on NASA TV; on-board cameras provided the unique views nine minutes into the flight.

Then the trouble struck, and the coverage ended.

The space station and its six-man crew were orbiting 250 miles above the Atlantic, just off the New England coast, when the Falcon soared. Astronauts are to use a hefty robot arm to draw the Dragon in and dock it to the station.

SpaceX tucked fresh fruit into the Dragon for the station residents; the apples and other treats are straight from the orchard of an employee's family. Also on board: 640 seeds of a flowering weed used for research, mouse stems cells, protein crystals, astronaut meals and clothing, trash bags, air-purifying devices, computer parts and other gear.

NASA's deputy administrator, Lori Garver, said using commercial providers is more efficient for the space agency. It's part of a long-term program, she noted, that has NASA spending less money on low-Earth orbit and investing more in deep-space missions. That's one reason why the space shuttles were retired in 2011 after the station was completed.

The goal is to have SpaceX, or Space Exploration Technologies Corp., and other private firms take over the job of ferrying astronauts to and from the space station in the next few years.

SpaceX -- so far the leader of the pack -- is aiming for a manned Dragon flight by 2015.

Competitor Orbital Sciences Corp. has yet to get off its Virginia launch pad. The company plans to launch a free-flying test of its Antares rocket and Cygnus supply ship in April, followed by a demo run to the space station in early summer. Then the so-called operational supply runs can begin.

Russia, Japan and Europe regularly make station deliveries as well, and Russia is the only option for astronaut rides. But only the Dragon is designed to bring back substantial amounts of research and used merchandise.

This Dragon is scheduled to spend more than three weeks at the space station before being cut loose by the crew on March 25. It will parachute into the Pacific with more than a ton of medical samples, plant and cell specimens, Japanese fish and old machinery, and used spacewalking gloves and other items.

SpaceX plans to launch its next Dragon to the station in late fall.

More than 2,000 guests jammed the Cape Canaveral launch site Friday morning to watch the Falcon take flight. It wasn't much of a show because of all the clouds.

The Associated Press contributed to this report.