Video: Press site view of Falcon 9’s launch with the Es’hail 2 satellite (members only)

Near the end of a ground-shaking test firing of Northrop Grumman’s solid-propellant Castor 600 rocket motor — the first stage of a new booster being designed to launch spy satellites and other national security payloads — a major part of the rocket’s big nozzle appeared to break apart, littering the test site with shards of debris.

SpaceX is counting down to liftoff Saturday of a Falcon 9 rocket with a commercial cargo craft heading for the International Space Station after engineers replaced a component in an upper stage steering system that grounded the launcher Tuesday.

A commercial Dragon cargo capsule is heading back to Earth Tuesday to conclude a 31-day stay at the International Space Station. The SpaceX-owned spacecraft was released from the station’s Canadian-built robotic arm at 10:59 a.m. EDT (1459 GMT), and the Dragon supply ship splashed down in the Pacific Ocean with nearly 3,400 pounds of cargo at 4:21 p.m. EDT (2021 GMT).