Live coverage: Atlas 5 countdown and launch journal

An Antares rocket carrying the Cygnus cargo ship has exploded moments after lift off from Wallops Island, Virginia.

The sixth and final satellite in the U.S. military’s network of ultra-secure, nuclear-hardened AEHF communications relay stations has arrived in Florida for final preparations for liftoff in March on a United Launch Alliance Atlas 5 rocket, the first of nearly 20 U.S. Space Force missions planned for launch in the first year of operations for the new military service.

A rocket engine that could power United Launch Alliance’s next-generation rocket has passed a major design review, clearing the way for full-scale hotfire testing starting next year and certification for test flights in 2019, according to Aerojet Rocketdyne, the powerplant’s developer.