An oxygen-supply system on the space station's Russian side has failed

• The oxygen-supply system on the International Space Station's Russian segment failed this week.
• Crew members aren't in danger, since the station has another oxygen system on its US segment.
• But the issue is the latest in a string on the station's Russian side — there has also been a broken toilet and an air leak.

The International Space Station is starting to show its age, particularly on the Russian side. In the last few months, a toilet in that segment went bust, an air leak got larger, and temperatures mysteriously increased.

Then on Wednesday, the Russian segment's oxygen-supply system failed, according to space agency Roscosmos. The Zvezda service module, where the system is located, has been in orbit for 20 years.

The failure coincided with the arrival of three new crew members, including NASA astronaut Kate Rubins – bringing the station's population to six. The crew isn't in danger, however, since the station has two oxygen-supply systems: one on the US side and one on the Russian side. The other system is functioning normally, according to Russian space agency Roscosmos.

"Nothing threatens the security of the crew and the ISS," a Roscosmos spokesperson told the AFP.

The station also keeps extra oxygen onboard in case both systems break down.

Still, the failure is another sign that Russian side of the orbiting lab is in need of upgrades. The station has already outlived its 15-year life expectancy.

"All modules of the Russian segment are exhausted," cosmonaut Gennady Padalka told Ria Novosti, a Russian state news agency.

Roscosmos did not immediately respond to Business Insider's questions about the failure.

An oxygen-system failure, a busted toilet, and an elusive leak

The ISS has two sides: the Russian Orbital Segment and the US Orbital Segment. The Russian segment contains the station's oldest module, the Zarya Control Module, which launched in 1998.

Its Zvezda Service Module, which launched in 2000, is the Russian segment's main module. It houses cosmonauts' living quarters: the kitchen, bathroom, and life-support systems, including the water-filtration system and the oxygen-supply system that just broke.

The report of the oxygen failure came after crew members spent months trying to find the source of an air leak on the space station. The ISS has been leaking at an above-average rate since September 2019, but crew members only started investigating in earnest over the summer.

In September, NASA and Roscosmos determined the leak was coming from the Zvezda module.

Daniel Huot, a NASA spokesperson, told Business Insider he wasn't "aware of any relation between this failure and the leak." The agency is working to get additional information, however.

Crew members still haven't pinpointed the exact location of the air leak, which they'll need to do in order to fix it. Officials maintain that the leak isn't major, though it seems to have contributed to the decision to push back Crew-1, SpaceX's first official mission for NASA.

A recent temperature increase that cosmonauts reported, meanwhile, was also in the Zvezda module, SpaceDaily reported. So was the toilet that broke down, though it has been repaired, according to Ria Novosti.