Russia launched a Soyuz spacecraft to replace a capsule that developed a coolant leak in December, stranding two cosmonauts and one NASA astronaut.

The Soyuz MS-23 spacecraft lifted from Russia's Baikonur Cosmodrome launch site in Kazakhstan on Thursday at 7:24 p.m. EDT and Friday at 5:24 a.m. local time.

The unmanned spacecraft will spend around two days in orbit, moving toward the International Space Station.

 It is planned to dock with the Poisk module, which is on the Russian-controlled segment of the space station, sometime after 8 p.m. EST on Saturday.

In September, cosmonauts Sergey Prokopyev, Dmitry Petelin, and NASA astronaut Frank Rubio arrived at the space station onboard the Soyuz MS-22 spacecraft. The Soyuz MS-23 will serve as their return vehicle.

Instead of carrying crew passengers, the Soyuz MS-23 rocketed into space on Thursday with a "Zero-G indicator," an item meant to float freely when the spacecraft encounters microgravity. The signal for this mission is a teddy bear attached to a string inside the cabin.

What caused the leak in the coolant?

Almost two months into the three men's mission, the MS-22 had a coolant leak, resulting in dangerous cabin temperatures for the crew's return flight. 

The Russian space agency Roscosmos and NASA moved swiftly to develop alternative vehicle designs. Roscosmos officials found that the leak was caused by a micrometeoroid impact that created a tiny hole.

After docking with the space station on February 11, a Russian cargo ship dubbed Progress encountered a similar coolant leak, casting doubt on the launch plans for the rescue vehicle. Three days later, Roscosmos announced through Telegram that the Soyuz MS-23 launch would be delayed until at least March while the agency probed the reason for the Progress vehicle's coolant leak.

Tuesday, however, Roscosmos said in an amended Telegram message that "external forces" were the source of the Progress spacecraft's leak.

NASA's deputy manager of the International Space Station, Dana Weigel, said at a briefing on Wednesday that the Russians are continuing to investigate both the Soyuz and Progress coolant leaks.

"They have organized a state committee to investigate the irregularities," she noted, stressing that the panel is investigating probable reasons for the capsules' takeoff through their orbital ride.

Crew change

MS-23 was initially scheduled to launch on March 16, carrying Roscosmos cosmonauts Oleg Kononenko, Nikolai Chub, and NASA astronaut Loral O'Hara to the space station.

• Also read Russia to Rescue ISS Astronauts Following Meteoroid Attack

Instead. Prokopyev, Petelin, and Rubio's tenure on the space station will be prolonged until the Soyuz MS-23 can transport them to Earth later this year. According to a report from Russia's state-run news agency TASS, this return might occur in September.

If this schedule continues, the three crewmembers will have extended their six-month space mission to around one year.

NASA's program manager for the space station, Joel Montalbano, said that the crew is in excellent condition and there is no need to hasten their return to Earth.

At a news conference held on January 11, Montalbano said that the team is "ready to help wherever we ask." 

"They are overjoyed to work and research in orbit, where we are now stationed in space. As a result, they are prepared to agree with any decision we make."

He continued, "I may have to fly them additional ice cream as a treat."

• Also read NASA considering SpaceX as a fallback for Russia's leaking Soyuz ship crew.

The launch of the Soyuz MS-23 spacecraft occurred only days before the launch of the Crew-6 mission by NASA and SpaceX. Crew-6 will include NASA astronauts Stephen Bowen and Warren "Woody" Hoburg, Sultan Alneyadi, an astronaut from the United Arab Emirates, and Roscosmos cosmonaut Andrey Fedoseyev.

NASA's Crew-5 astronauts will come home after their five-month mission on the SpaceX Crew Dragon shortly after the arrival of these four.

 NASA officials said this week that the coolant leaks suffered by the Soyuz and Progress spacecraft would not affect SpaceX missions and that no such difficulties have been identified with Crew Dragon vehicles.