The commercial cargo ship Dragon returned to Earth from the International Space Station on Sunday, bringing back nearly 2 tons of science experiments and old equipment for NASA.
SpaceX's Dragon splashed into the Pacific, just five hours after leaving the orbiting lab.
"Welcome home, Dragon!" the California-based company said via Twitter.
After a one-month visit, the SpaceX cargo ship was set loose Sunday morning. Astronaut Steven Swanson, the station commander, released it using the big robot arm as the craft zoomed more than 260 miles above the South Pacific.
"Very nice to have a vehicle that can take your science, equipment and maybe someday even humans back to Earth," Swanson told Mission Control.
The SpaceX Dragon is the only supply ship capable of returning items to Earth. The others burn up on re-entry. This was the fourth Dragon to bring back space station goods, with 3,500 pounds (1,600 kilograms) aboard; it came down off Mexico's Baja California coast.
NASA is paying SpaceX and Virginia-based Orbital Sciences Corp. to make station deliveries. Orbital is next up, next month. Russia, Europe and Japan also make occasional shipments.
SpaceX also is competing for the right to ferry station astronauts, perhaps as early as 2017.
The Dragon rocketed to the space station on April 18 with a full load and arrived at the orbiting lab two days later.
These missions continue even as Russian officials are threatening to end participation in the space-station program. As The Christian Science Monitor reported:
On Tuesday, Russian Deputy Prime Minister Dmitri Rogozin announced that the country would consider ending its participation in the space-station program in 2020; would prohibit the US military's use of a rocket motor that powers the Atlas V, one of two launch workhorses for defense and intelligence satellites; and would close down global-positioning-satellite monitoring stations in Russia unless it was allowed to build comparable monitoring stations in the US for its navigation satellites.
All of these threatened steps are in response to sanctions the US and Europe have imposed on influential Russians – including Mr. Rogozin – over Russia's annexation of Crimea and its efforts to destabilize eastern Ukraine.
But the Monitor also noted that the threats, with the exception of cutting off use of the Altas V rocket motor, seem relatively empty.
"I don't think the Russians could operate the station without the US. There's such a level of mutual interdependence that they both really need one another," notes John Logsdon, a professor emeritus of political science at George Washington University in Washington, D.C., and former director of the university's Space Policy institute.
As for Russia's role in transporting crews, halting that in 2020 would represent a hollow threat, since NASA is working with three companies that aim to begin launching crews to the space station by 2017, Congress willing. The three are Space Exploration Technologies (SpaceX), Boeing Company, and Sierra Nevada Corp.
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