Today’s flight will be the 14th for the Falcon 9. The 157-foot-tall rocket is named for the Millennium Falcon spacecraft featured in Star Wars; the number 9 is derived from the number of Merlin 1D engines on the first stage.
Puffs of gaseous oxygen can be seen venting away from the side of the rocket as it stands on the pad. This is normal, caused when small amounts of super-cold liquid oxygen warm up and boil off. The tank is topped off until the final minutes of the countdown.