After completing a dress rehearsal for launch day over the weekend, the four astronauts gearing up for liftoff Thursday on a SpaceX Falcon 9 rocket are in good spirits and spending time with their families in Florida before leaving the planet for a six-month expedition on the International Space Station. Forecasters with the U.S. Space Force’s 45th Weather Squadron predict an 80% chance of acceptable weather for launch early Thursday.

Using a new, uprated main engine for the first time on a rocket of its kind, a United Launch Alliance Delta 4-Medium+ vehicle will soar into space Wednesday night carrying a $566 million Air Force communications satellite.

The launch of two NASA astronauts dealt with two previous scrubs due to a valve issue on the Atlas 5 rocket and then a ground system issue at the launchpad. Liftoff happened at 10:52 a.m. EDT (1452 UTC) on Wednesday, June 5.