Video: Falcon 9 test-fired before fourth Starlink launch (members only)

A top secret payload developed in secrecy for the U.S. government is set to ride into orbit from Florida’s Space Coast aboard a SpaceX Falcon 9 rocket Thursday.

Ground crews finished the initial build-up of the last “single stick” medium-lift variant of United Launch Alliance’s Delta 4 rocket on its launch pad at Cape Canaveral last week in preparation for liftoff with a GPS navigation satellite July 25.

The towering structure to be used for liftoffs of NASA’s Space Launch System rolled from a construction site to launch pad 39B at the Kennedy Space Center in Florida this week, arriving at the seaside complex Friday for a week of fit checks.