NASA will bring ISS astronauts home early after medical problem

NASA will bring home a crew of four astronauts ahead of their scheduled return from the International Space Station due to a “controlled medical evacuation,” agency officials said Thursday.

It is the first time in the space station’s 25-year history that astronauts have returned early due to a medical problem.

NASA did not say who had the medical problem or what the problem was. However, the agency said the astronaut’s condition was stable.

The astronaut in question is one of four who arrived at the space station in August in one of SpaceX’s Crew Dragon capsules: Zena Cardman and Michael Fincke of NASA; Kimiya Yui from JAXA, the Japanese space agency, and Oleg Platonov from Roskosmos, the Russian space agency.

Their mission, known as Crew-11, was scheduled to end next month after the arrival of Crew-12, the next group of four astronauts. Now they will undock and return to Earth in the coming days.

“I have concluded that it is in the best interest of our astronauts to bring Crew-11 back before their scheduled departure,” said Jared Isaacman, NASA’s administrator since December 18, during a press conference Thursday evening.

This was not an emergency requiring an immediate return to Earth, Mr. Isaacman and other NASA officials said, but a prudent precaution because of the limited medical facilities on the space station.

“There remains the remaining risk and the question of what that diagnosis is,” said Dr. James Polk, NASA’s chief health and medical officer. “That means there is some risk to the astronaut on board. And so we always err on the side of the astronaut’s health and well-being.”

Dr. Polk described the astronaut’s condition as “absolutely stable.”

After Crew-11’s departure, three more astronauts will remain on the space station: Christopher Williams of NASA and Sergey Kud-Sverchkov and Sergey Mikaev of Russia. They flew to the space station on a Russian Soyuz spacecraft in November and are expected to stay there until the summer.

The smaller number of astronauts in orbit will be able to continue operating the space station, although they would likely have to reduce the amount of scientific work they do.

In a statement Wednesday, NASA said it was postponing a spacewalk scheduled for Thursday due to a crew member’s medical problem. Mr. Fincke and Ms. Cardman were scheduled to conduct a six-and-a-half-hour spacewalk on Thursday to modernize the station’s power system.

During the press conference, Dr. Polk said the medical problem had nothing to do with the spacewalk or space station operations.

According to NASA, it is Mr. Fincke’s fourth trip to the space station and Mr. Yui’s second. It is the first space flight for Ms. Cardman and Mr. Platonov.

As part of the crew’s mission, some of the astronauts will participate in studies to assess how space travel might affect astronauts’ health. This work examines, among other things, how the body processes B vitamins in space and how body fluids are redistributed in constant weightlessness.

A timetable for the return is expected to be announced in the next 48 hours. It is expected to continue following normal procedures for a splashdown in the Pacific Ocean west of San Diego.

Mr. Isaacman said NASA and SpaceX wanted to move forward with the launch of Crew-12.

He said an early launch of Crew-12 would have no impact on NASA’s Artemis II mission, scheduled to launch next month and sending four astronauts on a trip to the moon and back without landing.