"Go for capture." With those three words, SpaceX's Dragon capsule became the first privately launched spacecraft authorized to berth with the International Space Station. NASA Flight Director Holly Ridings issued the command this morning at 6:49am Pacific, after Dragon had spent the past evening performing demonstration maneuvers to prove its flight control capabilities near the ISS. Astronaut Don Pettit successfully grappled the module with a robotic arm 7 minutes later from aboard the space station.
Dragon will stay docked to the ISS for about a week, after which SpaceX will attempt to recover it for reuse in a reentry mission. If successful, SpaceX will be able to carry out its $1.6 billion contract with NASA to deliver supplies to the space station over 12 trips. This will hopefully free NASA and other government space agencies up to pursue other space exploration goals.
As we talked about on the latest episode of the podcast, the current SpaceX Dragon mission isn't just a test run--it's also delivering precious cargo in the form of supplies to the six astronauts on board the International Space Station (in addition to sold cargo space on the second rocket stage, for things like James Doohan's ashes). NASA has posted Dragon's full manifest online (PDF), which is fun to browse through. Unsurprisingly, half of the payload is dedicated to food, split into 160 rationed meals. 271 pounds of cargo storage bags and 22 pounds of computer equipment were also sent up. Space.com also reports that a stash of patches as souvenirs to commemorate the mission also made the trip. Talk about a collector's item.
All in total, Dragon's cargo weighed in at 1455 pounds including packing materials. SpaceX claims that the average cost of a trip for Dragon to reach the ISS will be $133 million, so that calculates to $91,000 per pound for this trip. While that sounds extremely expensive, Dragon's full payload capacity is actually 13,000 pounds, so future trips will average out to $10,000 per pound of cargo. By comparison, the Space Shuttle program ended up costing $20,000 per pound sent to space, and each mission cost $450 million.
As SpaceX initiates the era of commercial space flights to the ISS, I thought about how these private spacecraft would physically dock with public station stations. Unlike in science fiction film, a craft can't just push up against a station and initiate a pressure seal to pass cargo. Dock compatibility is kind of an important thing in space. As it turns out, all non-russian spacecraft use a docking port called the Common Berthing Mechanism, which is actually the same type of port that connects the separate sections of the ISS itself. The CBM dock offers a circular hatch 50 inches in diameter, which is wide enough to transfer cargo or crew members. Dragon is, after all, crew capable with a max capacity of seven passengers.