NASA and SpaceX have postponed today's planned launch of the SpaceX Demo-2.
They will try again Saturday.
Weather at the Kennedy Space Center in Florida is to blame for the postponement.
The Crew Dragon spacecraft, propelled by a Falcon 9 rocket, will carry NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station.
The launch is historic in part because it ends a nearly 10-year-long U.S. dependency on Russia for seats to space. It also marks the first time Elon Musk's private space firm, SpaceX, is launching astronauts. (ABC News has more here)