An unmanned Atlas 5 rocket has blasted off from the US, sending a long-awaited Orbital ATK cargo ship on its way to the International Space Station for NASA.
The Atlas 5, built and flown by United Launch Alliance, a partnership of Lockheed Martin and Boeing, lifted off from Cape Canaveral Air Force Station in Florida at 4.44pm on Sunday (0844 AEDT Monday) after three days of delays to wait out poor weather and high winds.
Sunday's launch reopens one of two US supply lines to the station, a $US100 billion ($A136.24 billion) research laboratory circling 400km above earth. Both cargo lines had been shut down by failed rocket launches.
Orbital, an aerospace and defence company with annual revenues of about $US4.4 billion, hopes to return its own Antares rocket to flight in May, following an October 2014 launch accident. Meanwhile, Orbital bought two Atlas rocket rides from ULA to resume work under its $US1.9 billion NASA contract.
NASA's second supply line, operated by privately owned Space Exploration Technologies, or SpaceX, is aiming to return its Falcon 9 rocket to flight this month following a botched station cargo run in June.
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Both companies hope to win follow-on station resupply contracts from the US space agency in January. They face competition from privately owned Sierra Nevada Corp, which is offering a robotic version of a small shuttle-like space plane called Dream Chaser. Boeing was eliminated from the competition last month.
With the arrival of its Cygnus capsule at the station, Orbital hopes to make up for lost time. The upgraded capsule, which is due to arrive on Wednesday, is loaded with more than 3500kg of food, clothing, computer gear, spacewalk equipment, science experiments and other supplies.
That is almost as much cargo as Orbital delivered during a test flight and its two successful cargo missions.
Cygnus will be the first US ship to reach the station since April, though Russia and Japan also fly freighters. Europe flew its fifth and final ATV cargo capsule in August.
The two US launch accidents, plus a failed Russian cargo run in April, have left the station's storage bins a bit empty.
NASA aims to keep a six-month supply of food aboard and is currently down to a four-month cushion. Toilet supplies run out in February, said station program manager Kirk Shireman.
