The crew of the International Space Station got its first look at the inside of its newest visitor – Space Exploration Technologies Corporation's Dragon cargo ship – Saturday morning and pronounced it a keeper.
The craft made aerospace history Friday by becoming the first commercially built and operated spacecraft to rendezvous and dock with another spacecraft on orbit.
“I spent quite a bit of time poking around in here this morning looking at the engineering and the layout, and I'm very pleased,” observes Don Petitt, a space station flight engineer and the crew member who guided the station's robotic arm as it grappled the craft for docking Friday morning.
SpaceX developed the Dragon to carry cargo and eventually crew, and based on his initial inspection of the craft's interior, riding in a human-rated Dragon “is not going to be an issue,” he said.
The mission began with a flawless launch May 22 from a pad at the Cape Canaveral Air Force Station in Florida. The crew opened the hatch to the cargo craft at 5:53 Eastern Daylight Time Saturday.
This mission, which is slated to end with Dragon's return to Earth May 31, is a demonstration flight. It consists of a final set of tests the craft and its controllers must pass in order to begin delivering on a $1.6 billion contract SpaceX has with NASA to carry cargo to and from the station between now and 2015.
Speaking from within what would be the Dragon's relatively spacious cabin as a capsule for humans, Dr. Petitt acknowledged that in the midst of the grab-and-dock process Friday, he and his colleagues, Andre Kuipers, a European Space Agency crew member, and NASA's Joe Acaba didn't have much time to contemplate the mission's place in history.
With an additional 24 hours to think about it, however, Petitt likened the event to the Golden Spike that symbolized the final link joining eastbound and westbound segments of the first transcontinental railroad line. The spike was driven into that last wooden rail tie on May 10, 1869.
“This is kind of the equivalent of the Golden Spike,” he said
“Nobody remembers who pounded that spike in,” he added, injecting some humility into the docking event. “The important thing is that the railroad was completed,” providing the initial infrastructure for widespread settlement of the American West.
On Sunday, the crew is scheduled to begin unpacking Dragon, which arrived with just over 1,000 pounds of clothing, food, and other items the crew needs. In addition, it's said to carry a surprise care package – something crew members look forward to with each arriving resupply flight.
After his informal inspection of Dragon's interior Saturday, Petitt noted that it carried about as much cargo as his pick-up truck. The craft consists of two segments – the pressurized capsule and an unpressurized “trunk” that doubles as the segment mating the capsule to the second stage of the Falcon 9 rocket at launch. SpaceX has designed an extended trunk for the craft.
Dragon is designed to loft up to 6 metric tons of cargo – somewhat less than Europe's automated transfer vehicle and about the same as Japan's cargo craft. Unlike these, however, which burn up on reentry, Dragon can return with up to 3 metric tons of hardware, experiment samples, and space-station components NASA might want to analyze or refurbish.
That capacity could increase if NASA needed it, said SpaceX founder and chief designer Elon Musk during a post-docking press briefing late Friday morning. SpaceX would just build a longer trunk, he said.
Indeed, returning cargo is one of the features Dragon is demonstrating on this mission. It is slated to return to Earth – splashing down in the Pacific May 31 – with about 1,400 pounds of “down mass,” including some space station components NASA wants to spruce up and return to the orbiting outpost. It's an important capability, NASA officials have noted. While a returning Russian Soyuz craft can carry small amounts of cargo from the station, until now, no other craft serving the station has the ability to bring hefty payloads back. That was the space shuttle's role.
Cargo craft built by Japan and Europe are flying only a combined seven missions between now and 2015, when the final Japanese mission launches. SpaceX and a second company, Orbital Science Corporation, are slated to fly 20 resupply missions through 2015, turning them into the main lifelines between Earth and the station, NASA officials say.