After getting off to a rocky start with an engine failure during launch Sunday, a commercial cargo capsule loaded with a half-ton of equipment and supplies, including ice cream, carried out a flawless final approach to the International Space Station early Wednesday, pulling up to within 60 feet so Japanese astronaut Akihiko Hoshide, operating the lab's robot arm, could pluck it out of open space for berthing.
Making the first of at least 12 cargo deliveries under a $1.6 billion contract with NASA, the SpaceX Dragon capsule, after a successful test flight last May, is the first commercially developed spacecraft to visit the station, the centerpiece of a push to restore U.S. resupply capability in the wake of the space shuttle's retirement last year.
Hoshide used station's robot arm to latch onto a grapple fixture on the side of the Dragon capsule at 6:56 a.m. EDT (GMT-4) as the two spacecraft sailed 250 miles above the Pacific Ocean west of Baja California.
"Houston, station on (channel) two, capture complete," Expedition 33 commander Sunita Williams radioed. "Looks like we've tamed the dragon. We're happy she's on board with us. Thanks to everybody at SpaceX and NASA for bringing her here to us. And the ice cream."
"We copy, Suni, nice flying," replied astronaut Rick Sturckow from mission control. "We'll put the post-capture configuration in work."
Williams and Hoshide planned to berth the Dragon capsule at the Earth-facing port of the forward Harmony module to complete the capture sequence.
The long-awaited mission began with a spectacular launch Sunday night from the Cape Canaveral Air Force Station in Florida. But during the climb to space, one of the Falcon 9 booster's nine first-stage engines malfunctioned and shut down, forcing the flight computer to fire the other engines longer than planned to compensate for the shortfall.
The Dragon capsule ended up in a useable orbit, but the engine failure prevented the Falcon 9 second stage from boosting a small secondary payload, an Orbcomm data relay satellite, into its planned orbit. As it was, SpaceX flight controllers had to quickly revise the Dragon rendezvous sequence to keep the craft on course and to conserve propellant.
All of that went off without a hitch and the spacecraft moved into position for grapple right on schedule.
The capsule will remain attached to the space station for the next three weeks while the lab crew unloads science gear, spare parts and crew supplies, including ice cream packed in a science freezer as a special treat for the three-person crew. The capsule will be re-packed with no-longer-needed hardware, failed components and experiment samples for return to Earth around Oct. 28.
Unlike Russian, European and Japanese cargo craft that routinely visit the station, the Dragon capsule was designed to make round trips to and from the lab complex, giving it the ability to bring major components and experiment samples back to Earth for the first time since shuttles stopped flying last year.
"The SpaceX Dragon is a really important vehicle for us because it supports the laboratory use of ISS, both in bringing cargo up to the space station and in bringing research samples home," said Julie Robinson, the space station program scientist at NASA Headquarters.
"It has a great return capability, it essentially replaces that capacity that we lost when the shuttle retired so that now we'll be able to bring home a wide variety of biological samples, physical sciences samples and we'll be able to bring home research equipment that we need to refurbish and then relaunch again."
The NASA contract with SpaceX requires the company to deliver 44,000 pounds of equipment and supplies over 12 flights. To pave the way for operational resupply missions, SpaceX carried out two successful test flights, one that tested the capsule's systems in a solo flight and another that included a berthing at the station last May.
The Dragon capsule measures 14.4 feet tall and 12 feet wide, with trunk section that extends another 9.2 feet below the capsule's heat shield that houses two solar arrays and an unpressurized cargo bay. The spacecraft can carry up to 7,297 pounds of cargo split between the pressurized and unpressurized sections.
For the first resupply mission, the Dragon capsule is loaded with 882 pounds of hardware, supplies and equipment including:
- 260 pounds of crew food, clothing, low-sodium food kits and other crew supplies
- 390 pounds of science gear, including a low-temperature Glacier freezer for experiment samples, fluids and combustion facility hardware, a commercial generic bioprocessing apparatus, cables for the Alpha Magnetic Spectrometer and research gear for the Japanese and European space agencies
- 225 pounds of space station hardware, including crew health care system components, life support system parts, filters and electrical components
- 7 pounds of computer gear
For its return to Earth, the Dragon spacecraft will be carrying 1,673 pounds of experiment samples and hardware, including:
- 163 pounds of crew supplies
- 518 pounds of vehicle hardware
- 123 pounds of computer gear, Russian cargo and spacewalk equipment
- 866 pounds of science gear and experiment samples, including 400 samples of crew urine
Under a separate $440 million contract with NASA, SpaceX engineers are working on upgrades to convert the Dragon capsule into a manned spacecraft that can ferry crews to and from the station. SpaceX managers believe they will be ready for initial manned test flights in the 2015 timeframe, assuming continued NASA funding. Two other companies, Boeing and Sierra Nevada, are developing their own spacecraft designs under similar contracts.