Live coverage: Delta 4 countdown and launch journal

SpaceX test-fired 27 main engines on a Falcon Heavy rocket Thursday in Florida, clearing a hurdle before installing three commercial communications satellites on the launcher for a mission to geostationary orbit later this month.

The last of NASA’s current-generation tracking and data relay satellites designed to link mission control with the International Space Station has been assigned for launch on a United Launch Alliance Atlas 5 rocket in October 2017, officials announced Friday.

SpaceX called off a launch attempt in Texas Monday for the Super Heavy booster and Starship launch vehicle, blaming a bad valve on the first stage. The next launch attempt for the world’s largest rocket is scheduled for Thursday, depending on weather and a fix for the valve problem.