I started dropping my eyes on a Russian space on Wednesday night

A Russian spacewalk was canceled at the last minute on Wednesday night when the spacecraft attached to the International Space Station suddenly burst into flames.

Cosmonauts Sergey Prokopyev and Dmitri Petelin were in spacesuits when the plane went down, when flight controllers were told to stand down while a leak in the Soyuz spacecraft was investigated. The spacewalk was released shortly before 10 pm ET (03:00 UTC).

The leak appears to have originated in an external cooling loop located at the aft end of the MS-XXII Soyuz spacecraft. Public affairs officer Rob Navias, who was handling NASA’s televised spacewalk, noted the spacecraft as dropping substantially. A video of the leak shows particles continuously streaming from the Soyuz, a more remarkable sight. This was most likely ammonia, which is used as a space coolant, although Russian officials have not confirmed this.

At no time were some of the comrades of the crew in danger at the station, among them Prokopyev and Petelin, and their compatriot Anna Kikina; NASA astronauts Frank Rubio, Nicole Mann and Josh Cassada; and Japanese astronaut Koichi Wakata. The leak was outside the station, not inside the laboratory circuit.

But the leak raises questions about the viability of the Soyuz space shuttle, which is a ride to Earth for Prokopyev, Petelin, and NASA’s Frank Rubio. The Soyuz launched this vehicle to the space station in September and is due to return to Earth next spring. After three hours on Monday night, the leak remained ongoing, showing no sign of abating.

The Soyuz is a tough ship, so it’s believed that it can’t do any damage to its ability to unlock from the space station and return to Earth. However, if Russian and NASA engineers consider that Rubio will be on board—determine that there is bile—a Soyuz replacement would be needed to fly the station. Soyuz vehicles have the ability to launch and dock automatically. But it would mean that until the time the space shuttle arrived, the three crew members would not have an emergency escape vehicle.

The remaining four astronauts flew to the station aboard the SpaceX Dragon spacecraft in October. That vehicle cannot accommodate seven people for the return to Earth.

Given the longevity of the rain, NASA is also likely to be concerned about the impact of all that ammonia on the surfaces of the space station and other space vehicles. A lot of ammonia will probably boil off the surface of the hardware over time, but it will certainly complicate operations as the US space agency works toward its December 19 space walk to install new solar suits.