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Space station crew brings SpaceX's Dragon cargo craft in for a hookup

NASA / SpaceX via Twitter

A video view from the International Space Station shows SpaceX's Dragon cargo capsule in the grip of the station's robotic arm, with Earth below.

Astronauts used the International Space Station's robotic arm to grab SpaceX's Dragon capsule on Sunday after the unmanned spacecraft made a dramatic recovery in orbit. The grapple operation reached its successful climax an hour ahead of schedule, proving that the unmanned capsule had fully recovered from a post-launch glitch that affected its propulsion system.

NASA and California-based SpaceX decided to go ahead with Sunday's rendezvous after the Dragon made a series of orbital maneuvers that demonstrated the craft's thrusters were operating normally. When the Dragon closed in to a distance of 33 feet (10 meters), the Canadian-built robotic arm reached out and latched onto an attachment on the cargo ship.

The robotic-arm grapple was originally scheduled to take place at 6:31 a.m. ET, but it occurred instead at 5:31 a.m., as the station was flying 253 miles (407 kilometers) over Ukraine.

NASA's Mission Control and the space station's astronauts exchanged congratulations. "That was a brilliant capture," NASA astronaut Kate Rubins told space station commander Kevin Ford from Mission Control.

Ford passed along his thanks to NASA's controllers in Houston as well as to SpaceX's mission control at the company's headquarters in Hawthorne, Calif. "It's not where you start, but where you finish that counts, and you guys really finished this one on the mark," Ford said. "You're aboard, and we've got lots of science on there to bring aboard and get done. So congratulations to all of you."

As the crew watched, the robotic arm's remote operators in Houston issued commands to pull the Dragon in for a hookup with the station's Harmony module. "The Dragon is ours!" Canadian astronaut Chris Hadfield wrote in a Twitter update. "Maneuvering it now on Canadarm2 to docking port, will open hatches. Look forward to new smells."

The capsule was berthed at 8:56 a.m. ET, and within a few hours, the station's astronauts hooked up the electrical connections, opened up the hatch from the Harmony module and took their first look inside the Dragon.

"Happy Berth Day," SpaceX exulted on Twitter

How a glitch was fixed
The cargo craft was launched on Friday from Cape Canaveral Air Force Station in Florida, atop SpaceX's Falcon 9 rocket. The ascent to outer space was trouble-free, but minutes after the Dragon reached orbit, SpaceX's controllers noticed that only one of the craft's four thruster pods was working. The thrusters control the Dragon's position in space, and at least three of the pods had to be operational to get NASA's clearance for the berthing.

It took several hours to resolve the glitch and get full thruster functionality. That caused SpaceX to miss its opportunity for a Saturday rendezvous. SpaceX's billionaire founder, Elon Musk, said it looked as if there was a stuck valve or a blockage in the thruster's oxidizer lines. Recycling the valves and sending a blast of pressurized helium through the line cleared the system, he said.

The maneuvers that followed gave NASA and SpaceX the confidence to go ahead with the hookup on Sunday. "The station’s Mission Management Team unanimously agreed that Dragon’s propulsion system is operating normally along with its other systems and ready to support the rendezvous," NASA said in a statement Saturday.

NASA said SpaceX voiced "high confidence there will be no repeat of the thruster problem during rendezvous, including its capability to perform an abort, should that be required." Fortunately, not a single hitch arose during the Dragon's approach.

Chris Hadfield via Twitter

Sub-Saharan Africa provides a backdrop for SpaceX's Dragon capsule in a photo taken from the International Space Station during the cargo ship's approach.


A video view from the International Space Station shows the SpaceX Dragon cargo capsule coming in for Sunday's berthing.


A view from one of the International Space Station's cameras shows the Dragon cargo capsule berthed to the Harmony module.

What's in the Dragon?
The Dragon is carrying more than 2,300 pounds (1,050 kilograms) of cargo, including experiments to study the growth of plants and mouse stem cells in zero-G. There are also spare parts for the station's air-recycling system, grapple bars for the space station's exterior, and a research freezer for preserving biological samples. The crew is getting clothing, personal items and food, including fresh fruit from an orchard owned by the father of one of SpaceX's employees.

The Dragon also is bringing the first copy of "Up in the Air," a single recorded by the band Thirty Seconds to Mars. That song will figure in a public-relations push later this month.

Once the space station's astronauts have finished unloading the cargo, they'll fill the Dragon back up with more than 3,000 pounds (1,370 kilograms) of stuff destined for return to Earth. The cargo craft is due to be set loose on March 25 for its splashdown in the Pacific.

This is the second of 12 resupply flights to be conducted under NASA's $1.6 billion contract with SpaceX. The first flight took place last October. SpaceX and another company, Orbital Sciences Corp., were granted the contracts to help fill the gap left by the space shuttle fleet's retirement in 2011. Orbital's cargo delivery service is expected to start later this year.

SpaceX is one of three companies receiving support from NASA under a separate program to develop crew-capable spacecraft for the space agency's use beginning in 2017 or so. SpaceX is working to upgrade its robotic Dragon capsule with extra safety equipment for crewed flight. The other two companies — the Boeing Co. and Sierra Nevada Corp. — are developing completely new spaceships. In the meantime, NASA is paying the Russians about $60 million per seat for rides to and from the space station.

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Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

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