Here's why NASA astronauts Suni Williams and Butch Wilmore are stuck, but not stranded, at the International Space Station after launching into space in June.

NASA's next crew of four was originally set to launch in February, with Wilmore and Williams returning home by the end of the month alongside two other astronauts. However, SpaceX requires additional time to ready the new capsule for flight, pushing the launch to late March at the earliest.