A private, unmanned spacecraft is once again on its way to deliver supplies to astronauts aboard the International Space Station after experiencing technical issues earlier on Friday.

Following a successful launch aboard SpaceX's Falcon 9 rocket from Cape Canaveral, Fla., Friday morning, SpaceX's Dragon capsule failed to fire up three of its four thruster pods.

As of 4:10 p.m. ET Friday, all four thruster pods were operating again, tweeted Elon Musk, chief designer and CEO for Hawthorne, Cali.-based SpaceX.

"Preparing to raise orbit. All systems green," he wrote.

"Orbit raising burn successful. Dragon back on track," Musk added two hours later.


The Dragon spacecraft's last run to the space station was in October, when it docked with the help of the Canadarm2. (NASA)

At a news conference earlier, Gwynne Shotwell, the president of SpaceX, assured the public that the spacecraft is in orbit and is stable, even though only two of the four thrusters were working at the time.

Musk said that as of Friday afternoon, it was too early to identify the cause of the problem, but it looked like there was a blockage or stuck valve that caused a drop in pressure in the oxidizer tanks of three of the pods. The oxidizer mixes with fuel in order to propel the spacecraft.

"It was a little frightening there," Musk said.

But all tanks had regained their normal pressure by mid-afternoon and the company believes the problem has been resolved.

"If that's the case, it's certainly going to be a huge relief," Musk said.

This is the first time in four flights of the Dragon capsule, including three to the International Space Station, where a problem has arisen, he said.

"I think it was essentially a glitch of some kind and not a serious thing," he added.

Dragon was originally scheduled to dock with the space station Saturday morning. However, NASA said the earliest possible time for docking is now Sunday morning, provided at least three of the thruster pods are operational and the data shows that the spacecraft can safely dock.

William Gerstenmaier, associate administrator for Human Exploration and Operations at NASA headquarters in Washington, said at the news conference that SpaceX's handling of the problems had so far been "extremely professional."

More than a tonne of space station supplies is aboard this Dragon for its second commercial resupply mission, 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, followed by its first commercial delivery in October.

Shortly after the delivery was back on track, Musk tweeted his relief: "Just want to say thanks to @NASA for being the world's coolest customer. Looking forward to delivering the goods!"

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 stem cells, protein crystals, astronaut meals and clothing, trash bags, air-purifying devices, computer parts and other gear.

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

With files from The Associated Press