Watch the Falcon 9 launch from pad 39A

On its second flight, SpaceX’s mammoth Falcon Heavy rocket hurled an Arabsat communications satellite the size of a school bus nearly one-quarter the way to the moon Thursday, days after NASA’s administrator identified the privately-developed rocket as a backup to the agency’s behind-schedule Space Launch System for sending astronauts back to the lunar surface.

The Starlink 17-9 mission added another 24 broadband satellites to its low Earth orbit constellation of more than 8,300. Liftoff from pad 4E at Vandenberg Space Force Base happened at 11:06 a.m. PDT (2:06 p.m. EDT / 1806 UTC).

Launching with a Spanish radar observation craft and the first two experimental satellites for SpaceX’s planned global broadband network, a Falcon 9 rocket fired away from California’s Central Coast shortly before sunrise Thursday after several days of delays.