Astronauts were stuck on the space station in February and had to be returned home

The capsule shot into orbit to pick up the test pilots, whose Boeing spacecraft returned to Earth empty earlier this month for safety reasons.

The change in rides left Nick Hague of NASA and Alexander Gorbunov of Russia to bring back Butch Wilmore and Suni Williams.

Because NASA rotates space station crews about every six months, this newly launched flight will not return until the end of February with two empty seats reserved for Mr. Wilmore and Ms. Williams.

Officials said there was no way to bring them back to SpaceX sooner without disrupting other planned missions.

When they return, the couple will have spent more than eight months in space. When they signed up for Boeing’s first astronaut flight, which launched in June, they expected they would only be away for a week.

NASA ultimately concluded that Boeing’s Starliner was too risky after a cascade of problems with the engines and helium leaks marred the flight to the orbiting complex.

The space agency excluded two astronauts from this SpaceX launch to make room for Mr. Wilmore and Ms. Williams on the return flight.

Ms. Williams has now been promoted to commander of the space station, which will soon return to its normal population of seven.

Once Mr. Hague and Mr. Gorbunov arrive this weekend, four astronauts who have been living there since March will be able to depart in their own SpaceX capsule. Their return home was delayed by a month due to the unrest on the Starliner.

Mr Hague noted before the flight that change was the only constant in human spaceflight.

“There is always something that changes. Maybe this time it was a little more visible to the public,” he said.

Because of his experience and handling of a launch emergency six years ago, Mr. Hague was appointed commander of the rescue mission.

The Russian rocket failed shortly after launch and the capsule carrying him and a cosmonaut catapulted from the top to safety.

Young NASA astronaut Zena Cardman and veteran space flyer Stephanie Wilson were pulled from the flight after NASA chose SpaceX to bring the stranded astronauts home.

The space agency said both are eligible to take part in future missions. Mr. Gorbunov remained under an exchange agreement between NASA and the Russian space agency.

“I don’t know exactly when my launch into space will be, but I know I will get there,” Ms. Cardman said from NASA’s Kennedy Space Center, where she attended the launch livestream.