Space station astronauts readied the world's first commercial supply ship Wednesday for its early morning return to Earth just like NASA's old-time capsules.
The unmanned Dragon capsule was due to splash down into the Pacific on Thursday, nine days after its historic launch to the International Space Station.
Astronaut Donald Pettit and his crewmates closed the hatch to the SpaceX Dragon and disconnected cables on the eve if its departure, after packing it with 1,400 pounds of experiments and old equipment for the ride back.
In the pre-dawn hours of Thursday, the plan was to reverse the steps Pettit took for Dragon's arrival last week, using the space station's robot arm to release the vessel. After flying solo around the planet a few times, the capsule was to aim for a Pacific splashdown, via parachutes, about 500 miles southwest of Los Angeles.
"Only a few countries have done this before, so we're not taking this lightly at all," SpaceX mission director John Couluris told reporters Wednesday.
The California-based SpaceX — Space Exploration Technologies Corp. — is the first private business to launch a spacecraft to the orbiting complex. If Thursday's descent goes well, the company will become the only supplier capable of bringing back a fair amount of space station gear. The Russian Soyuz capsules — now the only option for transporting astronauts — can fit three people and little else.
NASA wants to use Dragons to restock the station's pantry and return items like the space shuttles did until their retirement last summer. Other companies are also developing spacecraft for cargo and crews.
The plan set forth by President Barack Obama would have Dragons and other commercial craft ferrying station astronauts back and forth in the years ahead, setting NASA free to concentrate on expeditions farther afield, like asteroids and Mars.
SpaceX chief Elon Musk, the billionaire who helped create PayPal, said he can have crews flying his Dragons in three or four years.
None of the other visiting supply ships — the property of Russia, Europe and Japan — can return safely to Earth. They burn up in the atmosphere and consequently carry merely trash.
Only one Dragon has flown back from orbit before, during SpaceX's 2010 test flight.
Coulurlis said the descent remains "a very challenging phase of flight." Just in case, NASA requested that only nonessential items come back: old spacewalking gloves, empty science hardware and only a handful of actual experiment samples. The cargo that flew up on the Dragon also contained nothing vital.
No matter what happens Thursday — a successful splashdown or a failed entry — the company considers the events of the past week "a major success for us," Couluris said.
"The ability to get to space station on our first time, to not only rendezvous but then to berth, transfer cargo and depart safely, are major mission objectives," he said. "We would call that mission alone a success."
Although designed to be reusable, this Dragon will not fly again, Coulurlis said. He expects the capsule to eventually go on display.
The next Dragon launch, meanwhile, is targeted for September. The SpaceX Falcon 9 rocket for the flight already is at Cape Canaveral.