(NASA photo)

CAPE CANAVERAL, Fla. (March 3, 2013)--The unmanned commercial supply ship Dragon arrived Sunday at the International Space Station a day later than scheduled after a shaky start.

Station astronauts used a robot arm Sunday morning to grab the supply ship

The unmanned capsule is loaded with supplies and scientific experiments.

"The newly arrived scientific experiments delivered by Dragon carry the promise of discoveries that benefit Earth and dramatically increase our understanding of how humans adapt to space," said William Gerstenmaier, NASA's associate administrator for the Human Exploration and Operations Mission Directorate in Washington.

"Spaceflight will never be risk-free, but it's a critical achievement that we once again have a U.S. capability to transport science to and from the International Space Station. The science delivered and to be returned from the space station has the promise of giving us a unique insight into problems that we face on Earth. As the patch of Expedition 34 states: 'Off the Earth...For the Earth,’” he said.

California-based SpaceX, which tests its rocket motors in McGregor, struggled with the Dragon after Friday's launch because a clogged pressure line or stuck valve prevented the Dragon's thrusters from working.

It took flight controllers several hours to gain control and salvage the mission.

In the end, the Dragon arrived just a day late with its 1-ton load.

It will remain at the station most of March before returning to Earth with scientific samples.

SpaceX has a billion-dollar contract with NASA to keep the station supplied.