Watch NASA TV's coverage of the SpaceX Dragon cargo craft's berthing at the International Space Station.
By Alan Boyle
SpaceX's Dragon cargo capsule is ever so carefully closing in on the International Space Station for the first-ever hookup of a commercial spaceship with the $100 billion government-run orbital outpost.
The encounter would mark the first arrival of a U.S.-made spacecraft at the station since last year's retirement of NASA's space shuttle fleet, and potentially open the way for dozens of orbital cargo shipments. If the plan unfolds as NASA hopes, U.S. astronauts could be shuttled back and forth on the Dragon or similar spacecraft within just a few years.
Today's hookup comes after Tuesday's successful launch of the Dragon atop a Falcon 9 rocket, and represents the culmination of years of planning and hundreds of millions of dollars of spending by NASA and its commercial partner, California-based Space Exploration Technologies Corp., better known as SpaceX. The company was founded a decade ago by dot-com billionaire Elon Musk, with aspirations of eventually sending humans to settle on Mars.
But first things first: Today's operation marks the first full in-space test of the robotic Dragon spacecraft's procedure for approaching the station, and for that reason, every step along the way is being carefully planned out and checked over the course of several hours.?The first steps in the procedure were tested on Thursday, during a series of maneuvers that successfully brought the 14-foot-long, 12-foot-wide, gumdrop-shaped capsule within 2.5 kilometers (1.5 miles) of the $100 billion space station.
Today, a series of engine burns brought the Dragon even closer. "It's a great view," Dutch astronaut Andre Kuipers reported from the space station as he watched the craft approach. "The solar panels are nicely lit."
The craft took up a position 250 meters (820 feet) below the station. From that vantage point, the Dragon was put through a series of maneuvers to test the station-to-spacecraft communication system ??known as the COTS Ultra-high-frequency Communication Unit, or CUCU (pronounced like "cuckoo"). The space station's astronauts had the Dragon approach, then retreat, then approach, then hold its position.
NASA
This graphic lays out the series of maneuvers planned in advance of Dragon's berthing.
NASA
SpaceX's thermal imager provides a view of the International Space Station from 250 meters away.
When NASA gives the go-ahead, the Dragon will be brought to a distance of 30 meters (98 feet) for another instrument check, and finally to 10 meters (33 feet). At that point, NASA astronaut Don Pettit will use the station's 17-meter-long (60-foot-long) robotic arm to grab hold of a grapple attachment on the Dragon.
"Sort of like a cowboy ropin' a steer, we fly in the robotic arm and lasso the vehicle, and then we bring it up to one of the docking ports on station," Pettit said in a pre-flight NASA interview.
This rodeo will take longer than usual, however, due to the need to verify every move along the way. The robotic arm is due to grapple the Dragon at 7:59 a.m. ET. NASA says it will take another three hours or so to pull in the Dragon and get it hooked up to the station's Harmony module. NASA and SpaceX refer to this operation as a "berthing" rather than a "docking," because the Dragon is being passively pulled in rather than powering itself into the docking port.
NASA astronaut Cady Coleman, who underwent training for the berthing operation, said the robotic-arm moves had to be executed carefully to avoid damaging the Dragon or the station.?"If you stop too late, you could really hurt something," she said on NASA TV.
The berthing would put SpaceX in the company of four governmental space ventures?? NASA, the Russian Federal Space Agency, the European Space Agency and the Japan Aerospace Exploration Agency ? that have built vehicles capable of hooking up with the space station.?
If the operation plays out the way it's been planned, the hatch to the Dragon would be opened early Saturday morning. Pettit and the five other occupants of the station will unload about 1,000 pounds (460 kilograms) of cargo, including food, clothes, batteries and a laptop, plus 15 student-designed experiments. Then about 1,455 pounds (660 kilograms) of Earth-bound cargo?? including personal items from the crew as well as completed experiments and old equipment?? will be loaded up on the Dragon.
On May 31, the capsule would be detached from the station and sent back down toward a Pacific Ocean splashdown and recovery off the coast of Southern California. That part of the operation went off successfully during Dragon's first orbital test mission in December 2010, but this would mark the first-ever return of a commercial spacecraft from the space station. Russia's Soyuz capsule is the only other existing space vehicle capable of returning space station payloads.
If today's operation doesn't work out, NASA and SpaceX could make another attempt at a berthing?? and if the Dragon can't hook up at all this time around, another demonstration mission would have to be mounted. But once SpaceX proves that its system works reliably, the company could proceed with cargo resupply missions in earnest. It already has a $1.6 billion contract with NASA for 12 Dragon shipments through 2016.
Another company, Virginia-based Orbital Sciences Corp., is developing a cargo spacecraft known as Cygnus to take on space station shipments as well, under the terms of a $1.9 billion contract. The Cygnus has yet to be flight-tested, however.
In addition to the cargo contract, SpaceX is one of four companies that is receiving millions of dollars from NASA to produce spaceships capable of carrying astronauts. In SpaceX's case, the Dragon would be modified with a launch escape system, while the other companies ? Blue Origin, the Boeing Co. and Sierra Nevada Corp.?? are working with a variety of other spaceship concepts, ranging from capsules to Sierra Nevada's mini-space plane. The first astronaut flights could take place as early as 2017.
Until that time, NASA will have to depend on the Russians to transport U.S. astronauts on Soyuz spacecraft, at a cost of more than $60 million a seat. SpaceX and other players in the commercial space race say they can meet or beat that price.
The transition to commercial operations for orbital transport is a key part of the Obama administration's plan for future space exploration.
"We?re handing off to the private sector our transportation to the International Space Station so that NASA can focus on what we do best ? exploring even deeper into our solar system, with missions to an asteroid and Mars on the horizon," NASA Administrator Charles Bolden said after the Dragon's launch. "We?re committed to ending the outsourcing of work on America?s space program and bringing these jobs back to the United States."?
More about the mission:
Alan Boyle is msnbc.com's science editor. Connect with the?Cosmic Log?community by "liking" the log's?Facebook page, following?@b0yle on Twitter?or adding?Cosmic Log's Google+ page?to your circle. You can also check out?"The Case for Pluto,"?my book about the controversial dwarf planet and the search for other worlds.
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