Live video of launch pad 39A (members only)

A Falcon 9 rocket is again standing upright on launch pad 39A at NASA’s Kennedy Space Center in Florida after ground teams lowered the booster Friday to swap out mice heading to the International Space Station for medical experiments.

China led the world with 34 orbital launch attempts in 2019 — including two failures — followed by 22 flights from Russian-operated launch pads and 21 satellite delivery missions originating from U.S. spaceports, all of which were successful.

Engineers scrambled to keep NASA’s billion-dollar asteroid-bound OSIRIS-REx spacecraft on track for its launch last week in the aftermath of an explosion a mile away at SpaceX’s launch pad at Cape Canaveral.