Snapshots from Atlas 5 launch

United Launch Alliance’s first Vulcan Centaur rocket completed a critical test-firing of its Blue Origin-built BE-4 main engines Wednesday night, clearing one of two remaining technical hurdles before the launcher is cleared for its inaugural flight later this year.

A hydrogen-fueled main engine and four solid rocket boosters combined to propel a United Launch Alliance Delta 4 rocket off its launch pad at Cape Canaveral on March 15, successfully sending a U.S. Air Force communications satellite into orbit.

A sophisticated combat-ready U.S. military missile warning satellite moved to its launch pad at Cape Canaveral Space Force Station Saturday on top of a United Launch Alliance Atlas 5 rocket, ready for liftoff Monday afternoon.