Watch live: Vice President Pence visits Kennedy Space Center

With an eye on fast-moving Hurricane Irma, SpaceX successfully launched a Falcon 9 rocket from the Kennedy Space Center Thursday while NASA and contractor personnel rushed to prepare the sprawling spaceport for extreme winds, torrential rain and a threatening storm surge.

Astronauts Doug Hurley and Bob Behnken say SpaceX’s Falcon 9 rocket was a “very pure flying machine” as it sped their Crew Dragon spaceship into orbit, but they said they were surprised by the rougher-than-expected ride on the Falcon 9’s powerful upper stage.

Fueled segments of the solid rocket boosters that will lift off on the first flight of NASA’s Space Launch System have arrived at the Kennedy Space Center in Florida, but officials will hold off on stacking the boosters until the SLS core stage completes a crucial test-firing later this year.