Photos: Atlas 5 rolls out for launch

SpaceX’s next Falcon 9 rocket arrived at Kennedy Space Center’s pad 39A on Thursday for a hold-down engine firing ahead of launch next week with the U.S. Air Force’s X-37B spaceplane. The brief engine ignition occurred at 4:30 p.m. EDT (2030 GMT).

A critical test-firing of the Space Launch System’s core stage engines cut off about a minute into a planned eight-minute burn Saturday on a test stand at NASA’s Stennis Space Center in Mississippi. The rocket’s four engines ignited at 5:27 p.m. EST (2227 GMT) for a test that was to pave the way for the core stage’s shipment to the Kennedy Space Center for launch preparations.

The top secret intelligence-gathering payload for the U.S. government set for launch Tuesday on top of a Delta 4-Heavy rocket is likely the next in a line of sensitive eavesdropping satellites designed to intercept radio signals and other communications traffic from adversaries around the world.