Cracks in ISS Russian Module: The Background to NASA’s Emergency Evacuation Order

Structural cracks in the PrK module attached to Russia’s Zvezda service module on the International Space Station (ISS) are worsening. According to Ars Technica, the issue has persisted since 2019, and on June 5, 2026, NASA ordered astronauts to take emergency shelter in a Crew Dragon spacecraft.

Origin and Timeline of the Incident

The cracks have appeared in the PrK module, part of the Russian segment of the ISS. This module is a passageway from the Zvezda service module to the docking port. Russian cosmonauts pressurize this tunnel to access Progress cargo spacecraft for loading and unloading supplies.

The problem was first identified in 2019, and since then Russian cosmonauts have repeatedly performed temporary repairs using a sealant called “Germetall-1.” In early 2026, Roscosmos reported that the crack progression had stabilized, but it worsened again in May and accelerated sharply in early June.

Russian Repair Proposal Sparks the Incident

On June 5, Roscosmos began work on a more extensive inspection and structural repair. However, the repair method proposed by Russian authorities raised concerns at NASA, prompting the U.S. side to take the unusual step of ordering an emergency evacuation to ensure astronaut safety.

The specific proposal has not been made public, but NASA has serious concerns about the structural integrity of the PrK module. Bob Cabana, a former astronaut and former NASA senior official interviewed by Ars Technica, said in late 2024: “NASA has expressed concerns about the structural integrity of PrK and the possibility of a catastrophic failure.”

Structural Weakness from Corrosion

The cause of the cracks is corrosion. The PrK module is an aging tunnel structure that develops cracks internally as pressure fluctuates. The severity of the problem lies in the possibility that this module could completely fail without warning. There is a risk that the module, while under pressure, could completely lose function as if “melting.”

The Russian side withdrew its initial repair proposal and agreed to conduct additional measurements and inspections. NASA strongly supports this decision, and the astronauts have been cleared from evacuation status and have returned to normal operations.

Differences in U.S.-Russian Views

Ars Technica reports that NASA has refrained from publicly discussing the severity of this issue out of consideration for the Russian side. However, the crack problem has been a long-running, behind-the-scenes dispute between the two space agencies.

NASA’s official statements have been limited, and Roscosmos has only issued brief comments. Differences in the stances of the two agencies regarding information disclosure make it difficult to fully grasp the situation.

Editorial Opinion

Short-Term Impact

The emergency evacuation should be seen as a serious warning about the limits of safety in ISS operations. In the coming months, the detailed inspection results from the Russian side will shape cooperation between the two agencies. If the PrK module is deemed irreparable, it may become necessary to permanently seal that section or, in some cases, to review operations of the entire Russian segment. This would directly affect ISS science experiments and resupply schedules.

Long-Term Perspective

The ISS was approved for a lifespan extension in 2024, allowing operations to continue until 2030. However, structural aging is inevitable. The PrK issue provides reason to reconsider the overall life assessment of the space station. With ongoing geopolitical tensions between the U.S. and Russia, maintaining technical cooperation is expected to become even more challenging. Comparisons with China’s Tiangong space station and the acceleration of private space station plans may also be relevant.

Questions from the Editorial Team

This incident raises important issues concerning both the “limits of operational life” in space development and “political cooperation.” Whether the U.S. and Russia can continue to cooperate in the face of technical problems, or whether they will shift toward nationally led space station plans, remains to be seen. Another point of interest is whether alternative space station proposals from the private sector (such as Axiom Space) will become more realistic against the backdrop of such aging problems. The industry as a whole must discuss the limits of structural repair technology in space and the appropriate safety standards for long-duration missions.

References

• Russia appears set to finally address long-term, serious space station cracks - Ars Technica — Published June 15, 2026