A United Launch Alliance (ULA) Atlas V rocket carrying the OA-4 mission lifts off from Space Launch Complex 41. The mission, flown for Orbital ATK under NASA’s Commercial Resupply Services contract, marks the first time the Cygnus has flown on an Atlas V rocket. This was ULA’s 12th launch in 2015. At just over 8 tons, Cygnus is the heaviest payload to launch atop an Atlas V rocket.