Video: Atlas 5 launch with GOES-S viewed from KSC press site (members only)

The nine Merlin main engines at the base of a recycled Falcon 9 rocket booster ignited Thursday night for several seconds during a pre-flight test-firing on a Cape Canaveral launch pad, clearing a major hurdle ahead of a scheduled May 31 liftoff with a high-power communications satellite for SES.

Watch the Atlas 5 rocket and OSIRIS-REx asteroid sample return spacecraft pre-launch news conference and the mission science briefing held on Launch-minus 2 days at the Kennedy Space Center.

A United Launch Alliance Delta 4-Heavy rocket lifted off from Cape Canaveral at 8:09 p.m. EST Thursday (0109 GMT Friday). The long-delayed mission is carrying a classified spy satellite into orbit for the National Reconnaissance Office.