The unmanned Cygnus capsule has been launched for its first commercial delivery mission to the International Space Station (ISS) on Thursday afternoon after delays due to bad weather.
The 13-story Antares rocket, carrying the Orbital Sciences-built cargo capsule, lifted off from its launch pad on Wallop Island Virginia at 6.07pm GMT despite a small liquid oxygen leak on a ground maintenance line having been spotted hours before the launch. The leak was promptly resolved by Orbital Sciences technicians.
"We're in good shape," Orbital Sciences Executive Vice President Frank Culbertson told reporters after launch.
Cygnus’s first commercial mission was previously postponed several times, first due to a failure of the ISS cooling system in late December that required emergency repairs. Later delays were caused by severe and extremely cold weather and intense solar activity. Both conditions could possible cause damage to critical rocket systems.
Cygnus is scheduled to dock with the ISS early in the morning on Sunday 12 January. The first commercial mission, a part of a $1.9bn (£1.15) Commercial Resupply Services (CRS) contract with NASA will deliver 1,461kg of equipment and supplies to the orbital outpost including science experiments, computers and replacement parts for NASA's spacesuits. The capsule also carries food, fresh fruit and belated Christmas gifts for the crew.
Cygnus will remain docked at the station until 18 February. Before departing it will be filled with about 1,300kg of waste which will burn together with the capsule in the Earth’s atmosphere during re-entry above the Pacific Ocean.
Orbital Sciences first tested its Antares rocket in April 2013 and performed a successful test mission to the ISS five months later, becoming only the second private company in the history to dock a spacecraft at the station.
Nasa has now two private providers capable of carrying supplies to the ISS, with SpaceX and its Dragon capsule being in service since 2012. Unlike Orbital Sciences that opted for a disposable vehicle, building a new capsule for every mission, SpaceX is using a reusable Dragon capsule, which is scheduled for its next cargo delivery on 22 February.
Nasa's contract with Orbital Sciences covers eight re-supply mission to be conducted between 2014 and 2016. However, the contract could be extended following the decision the keep the ISS operational until at least 2024.