Four astronauts launched on Friday en route to the International Space Station.

A SpaceX Falcon 9 rocket lifted off at 7:03 p.m. Eastern time from NASA’s Kennedy Space Center in Florida.

This is a routine rotation of crew on the space station, but it is garnering extra attention because it will allow the return to Earth of Suni Williams and Butch Wilmore, two NASA astronauts whose brief scheduled visit to the space station last June was unexpectedly stretched to more than nine months.

The stay of Ms. Williams and Mr. Wilmore in orbit was extended at least two more days when the first attempt at launching this mission on Wednesday was called off with less than 45 minutes left in the countdown. Mission controllers were unable to solve a hydraulic issue with a clamp arm that holds onto the rocket until a few minutes before launch.

On Friday, the countdown proceeded smoothly with the rocket lifting off on time into the mostly clear skies. As typical, the booster of the Falcon 9 dropped off and landed on a pad near the launch site while the second stage continued to orbit.

A few minutes after the second stage completed its engine burn, the Crew Dragon spacecraft with the astronauts separated.

“Thank you to all of the teams from across the world who contributed to the launch today,” Anne McClain, the NASA astronaut who serves as the commander of the mission, known as Crew-10. “Spaceflight is tough. Humans are tougher.”

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