Time-lapse video: The Falcon Heavy goes vertical again

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.

Four veteran astronauts have been selected to train for launch aboard new commercial crew capsules being built by Boeing and SpaceX that are intended to ferry astronauts to and from the International Space Station starting in 2017, NASA announced Thursday.

The mission was the second of potentially three Falcon 9 flights set to take place this week. Liftoff from pad 40 at Cape Canaveral Space Force Station happened at 10:35 p.m. EDT (0235 UTC).