The ISS is cracking. But air leaks are just one of its problems.

There are cracks in the ISS. The International Space Station is leaking air.

We’ve known about this air leak for years, and have done a lot to try and fix it, and haven’t been able to. It’s just getting worse, to the point NASA recently elevated the issue to the highest level of risk in their internal system. The fact is, we don’t even understand exactly why the leak is happening, much less how to fix it.

And yet NASA is considering keeping the ISS in orbit past 2030.

Is that even possible at this point? What are the major issues facing the ISS? Is the deorbit plan—to have SpaceX design and build a new vehicle in just five years—feasible? Will private space stations be ready by 2030? And what happens if Russia doesn’t agree to all this, as they’re only committed to the ISS through 2028??

The OIG report and ISS’s current situation

A report came out in the last few weeks from the NASA Office of the Inspector General that basically outlines the risks of operating the ISS through 2030 (or possibly beyond.) Right now, the ISS is scheduled for retirement in 2030 and controlled deorbit in early 2031.

But NASA has also made clear that they don’t want to retire the ISS if there’s nothing to take its place—they want to hand the torch over to private, commercial space stations that can continue the work of the ISS in low Earth orbit, and they want them in orbit before the end of life of the ISS.

That means that the contingency plan that NASA is currently working on is an indefinite extension of the ISS’s life past 2030. They don’t especially want to do this, and it’s not the primary plan—but it’s a very real (and honestly likely) possibility. The question is: Can the ISS even handle that? The ISS is not in great shape, and every year that goes by it gets worse.

The air leak in question is located in the Zvezda Service Module is on the Russian side of Space Station, and it’s the third oldest module on the ISS, after Zarya and Unity. It launched in July of 2000. If you know how spacecraft work, Zvezda is basically the ISS’s service module. It provides power, life support, docking ports for Progress cargo modules and Soyuz spacecraft, sewage processing, and is the primary source for the ISS’s propulsion systems.

It’s not all that surprising that one of the early Russian modules is the one that’s falling apart. These early modules have undergone significant stress as the ISS has been expanded and added onto. Plus the original structural frame of Zvezda dates back to the mid-1980s. It was intended as a successor to the Mir space station, called Mir 2.

At the time the Russian space program was so strapped for cash that they launched Zvezda on a rocket emblazoned with the Pizza Hut logo, for which the company reportedly paid over a million dollars. (The first U.S. module Harmony was also modified from what was supposed to be a U.S. space station. And guess who built that module? The Boeing Company.)

If you’re getting the sense here that the construction of the ISS was a little haphazard—you’re not wrong. Everyone was basically scrambling to repurpose plans and hardware from their individual space stations that didn’t pan out.

Knowing all this, it’s not surprising that 24 years later, the ISS is falling apart a little bit.

The air leak in Zvezda

Okay, so: What’s going on with this air leak?

NASA has known about it since 2019. It’s located in a vestibule that separates a Progress docking port from the rest of the service module, called the Service Module Transfer Tunnel, and the leak has gotten progressively worse. I say “leak” in the individual, but that’s technically inaccurate because we’re talking about multiple leaks of varying sizes. Some of them, NASA and Roscosmos have been able to pinpoint the source and do work mitigating or fixing them. Others, they haven’t been able to figure out. This has been going on for five years, and everything has gotten worse.

The ISS normally leaks a lot of air in its normal day to day operations. The stable leak rate is around 0.6 pounds-mass of air per day. Anything above that requires NASA and Roscosmos to investigate the source. Well in September of 2019, that increased dramatically to 1.2 pounds per day. Then a year later, it dramatically increased again to 3 pounds per day. In 2022, NASA and Roscosmos identified multiple air leak sources and fixed them, but only managed to bring the leak rate down to 1.7 pounds per day. After 2021, they brought it down to 0.2 pounds, but it’s been an ongoing problem.

That’s how they’ve functioned for years, with this leaky vestibule. At this point we know that the Service Module Transfer Tunnel is cracking; that’s why it’s leaking. But why is it cracking, when nowhere else on the Station seems to have that problem?? That’s the mystery.

They’ve basically ruled out a debris or micrometeoroid strike. Is it defective workmanship? Is it stress from docking and undocking? The analysis says, based on what the Service Module Transfer Tunnel has experienced, it shouldn’t be in this state. Yet it is, so something is going on.

The location of the leak is actually incredibly lucky because it can be sealed off by an airlock to mitigate air loss. Right now on the ISS, they keep the hatch on that area closed, and so it doesn’t really impact the day to day of Space Station. If the leak gets significantly worse, and they feel like it’s a present danger, they can just close off the tunnel completely. They’ll lose a valuable docking port, but it is an option.

But without understanding why these cracks are happening, it remains a serious danger to the astronauts and cosmonauts aboard the ISS and severely complicates any plan to extend the life of the Space Station.

Especially because — the leak is getting worse! Both NASA and Roscosmos maintain that the condition of the Service Tunnel Transfer Module isn’t an immediate risk to the structural integrity of the ISS, But in February of this year, the leak rate increased again to 2.4 pounds per day, and then two months later it went up again to 3.7 pounds.

NASA and Roscosmos have done work to mitigate this leak rate—the current leak rate isn’t clear but some repairs have been done, and Russia is limiting operations in the area and keeping the hatch closed when the airlock isn’t in use. But also, another problem: NASA and Russia haven’t actually agreed on what the highest maximum acceptable leak rate is, which means there’s no consensus on the point at which that part of the Space Station needs to be sealed off permanently.

But the air leak isn’t the only problem here

This is a hard situation. And it’s just one of the problems facing the ISS right now. There are others that are a real problem when it comes to the idea of extending ISS operations past 2030. Right now, there isn’t really a viable private space station that looks like it will be ready by then, which means it’s very possible NASA will be looking to extend ISS operations.

Let’s talk about the practical problem with that: Russia hasn’t agreed to any plan to extend ISS operations past 2030, and core modules of the ISS are dependent on one another—you can’t separate the U.S. and Russian parts of the ISS and use them independently. We can’t keep the ISS in orbit without the Zvezda module’s thrusters and the boosts that the Progress spacecraft provide. Literally, as the ISS is configured right now, without the Russian Progress spacecraft, we can’t keep the ISS in orbit.

Lack of redundancy is a huge concern

And as the NASA Office of the Inspector General points out, we’re dependent on Russia in other ways too. Many times, over the course of the history of the ISS, the Russian Soyuz has been the only way to get NASA astronauts to and from the International Space Stations—from the grounding of the Shuttle fleet after the Columbia disaster to the long period between the end of the Space Shuttle program and the launch of SpaceX’s Crew Dragon.

And still, we don’t have redundancy. The U.S. only has one operational crew spacecraft to take astronauts to and from the ISS (and as of right now, NASA still hasn’t decided when Boeing Starliner will fly again, and if there will be another crewed test flight required. We’re looking at June of 2025 for them to even make that decision, but the spacecraft’s fate is still uncertain.)

Three times in the past few months, the SpaceX Falcon 9 rocket has been grounded after anomalies with the second stage or after landing. They’ve all been relatively short periods, the longest one was only about two weeks, but right now the SpaceX Falcon 9 rocket is the only way we have to get crew to and from the Space Station besides the Soyuz.

What’s even worse is that it’s also the only way we have to get cargo to and from the ISS besides the Progress. SpaceX holds one of the commercial cargo contracts with the Dragon spacecraft. Northrop Grumman’s Cygnus vehicle is the other spacecraft that resupplies the ISS. They’re currently in between rockets, waiting on the new Antares that’s supposed to debut next year. Until it does . . the Cygnus is launching on a SpaceX Falcon 9. The Falcon 9 is literally the only way the U.S. has to get crew or cargo to the ISS. (If you’re wondering about the Sierra Space Dream Chaser, it’s delayed, we’re hoping the first cargo flight will be in 2025.)

Again, as I’ve said many times: SpaceX’s Falcon 9 rocket is a great and reliable launch vehicle, the workhorse of the launch industry. These anomalies have been minor, and none of them affected the mission. But this kind of dependence on one launch vehicle is NOT good, and NASA’s plans for redundancy haven’t generally gone well (again, I give you the case of Boeing Starliner).

And if Boeing Starliner has taught us anything after that whole “return without spacesuits contingency plan” it’s that having extra spacecraft docked to the ISS for an emergency is a good thing. We just don’t have that capability at the moment.

Right now, there are still crew swaps going on between cosmonauts and astronauts—one NASA astronaut trains with a Russian crew and flies on a Soyuz, and vice versa. But this cooperation is scheduled to end in 2025 (though NASA is negotiating with Roscosmos to extend it).

Micrometeoroid strikes, replacement parts, and NASA’s budget

That’s not the only issue facing a possible extension to the life of the ISS—the ISS is increasingly vulnerable to micrometeoroid and debris strikes as it ages.

A micrometeoroid strike is what likely damaged a Soyuz capsule in 2022 and led to NASA astronaut Frank Rubio’s record-breaking spaceflight: an extension from 6 months to over a year because Russia had to send up a second vehicle to bring the astronauts back.

And more and more parts need to be replaced. Have you tried replacing a part on something that’s over 20 years old? A lot of the time it’s easier to just replace something than try and find that replacement part, but that’s not an option with the ISS. The core modules weren’t designed to be replaced or swapped out. So NASA is doing their best to order and have replacement parts on hand, but it’s getting more tricky.

Back in June, NASA actually had to pull some of Butch and Suni’s personal suitcases off of Boeing Starliner because they had to get a replacement urine pump part up to the ISS as soon as possible. Until it got fixed, astronauts were just having to store urine. You might have been asking “why don’t they just have this replacement part on board if it’s so crucial” — this is why, they’re hard to come by and take an increasingly long time to get. As the ISS gets older and older, this is going to become a bigger problem. They’re also getting more expensive.

Which brings me to the budget issues. NASA is already cancelling programs left and right because they aren’t in a good budget environment.

The ISS costs NASA about $4.1 billion per year for operations and research, which is around 16 percent of NASA’s budget. That’s a huge cost that’s just going to increase as the ISS gets older, and it’s unclear if NASA can even afford to extend ISS operations past 2030. They don’t seem to have the budget for it right now.

The U.S. De-orbit Vehicle may not be ready on time

The ISS was originally scheduled for deorbit in 2015, and that’s been extended through 2020, 2024, and now 2030. The question is will it happen again? It’s not like NASA can make that decision unilaterally. The ISS is managed by NASA, Roscosmos, the CSA (Canadian Space Agency), JAXA (Japanese Space Agency), and the ESA (European Space Agency). All the partners except Russia have agreed to extending the ISS’s lifetime through 2030. Russia has only agreed to 2028.

If at this point you’re asking yourself “Wait, if Russia is currently only in until 2028, what’s going to happen between 2028 and 2030” you are at the same place I am. Let’s say the life of the ISS isn’t going to be extended and we’re all sticking with the 2030 date. The plan is to start the end of life process for the ISS with Progress spacecraft and then finish it with the U.S. Deorbit Vehicle built by SpaceX.

Except as the NASA Office of the Inspector General reports point out, it takes an average of eight and a half years from the awarding of a contract for a new vehicle to the first operational flight. Now, the USDV is based on heritage Dragon hardware—they’re just going to add some propulsion and other systems to the trunk of the spacecraft. That will certainly cut down on development time. But this contract was awarded in June of 2024. There’s a lot of questions of whether the vehicle will be ready by the time it needs to launch in 2030.

If it’s not, we will have to delay deorbit until it is ready, and again, Russia is only committed to the ISS through 2028. Earlier this year, the U.S. and Russia signed an agreement about their roles and responsibilities if an emergency deorbit of the ISS is required, which is good because the thing weights 925,000 pounds (420,000 kg) and we don’t want it coming down in an uncontrolled manner. But Russia hasn’t agreed to the current deorbit plan (that doesn’t mean they won’t, but until they do agree there will be a lot of uncertainty around it.)

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