Rocket company SpaceX will make a second attempt in the coming hours to get Nasa astronauts Doug Hurley and Bob Behnken into orbit.
Their flight to the International Space Station (ISS) on Wednesday was postponed because of poor weather at Florida’s Kennedy Space Center.
Saturday’s forecast is not brilliant. The meteorologists say conditions will probably be touch and go again.
The lift-off is scheduled for 15:22 EDT (19:22 GMT; 20:22 BST).
There’s huge focus on Hurley’s and Behnken’s mission because it will mark the first time that the United States has been able to launch its astronauts to the ISS since the retirement of Nasa’s space shuttles in 2011.
It will also be the first occasion that the US space agency has used a private company to transport one of its crews to orbit.