Watch conditions at Kennedy Space Center during Tropical Storm Isaias

Stormy weather near NASA’s Kennedy Space Center kept SpaceX’s Falcon 9 rocket on the ground Thursday, delaying liftoff of a commercial supply ship with equipment and experiments for the International Space Station until Saturday.

SpaceX is replacing two engines on the Falcon 9 booster set to launch four astronauts next month on the company’s first operational Crew Dragon flight to the International Space Station, following an investigation that revealed a subcontractor failed to adequately clean out narrow vent ports on multiple engines across the company’s fleet, officials said Wednesday.

The mission was the 12th launch of a Falcon Heavy rocket to date. The rocket lifted off from pad 39A at NASA’s Kennedy Space Center at 10:13 a.m. EDT (1413 UTC) on Wednesday, April 29.