Video: Take a virtual ride on the Atlas 5 launch pad emergency ziplines

A United Launch Alliance Delta 4 rocket blasted off from Vandenberg Air Force Base in California at 3:40 a.m. local (6:40 a.m. EST; 1140 GMT) today to place a secret payload into space for the National Reconnaissance Office. Follow the mission in our live journal.

The 75th Atlas 5 rocket rolled to its launch pad at Cape Canaveral on Wednesday, a day before it was scheduled to lift off with a U.S. Air Force satellite to provide warnings of missile launches that might threaten U.S. territories and allies.

A new launch date has been established — June 9 — for the Delta 4-Heavy rocket to carry a classified satellite into space for U.S. national security needs.