In a rare bit of good news for both Moscow and Washington, engineers have identified and sealed the persistent leak in the Zvezda module of the International Space Station that first surfaced in 2019. The affected module, launched in July 2000 on a Proton rocket, had developed a slow but persistent air loss that prompted long-running inspections and mitigation measures aboard the station. Repair work done in late 2025 resolved the immediate depressurization source, halting the measurable leak after years of monitoring. While the fix restores normal station operations for now, experts caution that decades-old hardware can develop new faults and continued vigilance will be required.
Key Takeaways
- The leak in the Zvezda service module, which first appeared in 2019, has been stopped following targeted repairs in late 2025.
- Zvezda was launched in July 2000 on a Russian Proton rocket and has been in service for more than 25 years.
- The November 2025 Soyuz launch from Baikonur caused collateral damage to Site 31’s mobile gantry, putting the pad temporarily offline.
- NASA’s internal schedule lists a Progress cargo launch on March 22, 2026, and another on April 26, 2026, indicating confidence in pad repairs.
- The next crewed Soyuz mission, MS-29, is scheduled for July 14, 2026, and will carry NASA astronaut Anil Menon to the ISS.
- Primary crew from the November launch included Roscosmos cosmonauts Sergei Kud-Sverchkov and Sergei Mikayev and NASA astronaut Christopher Williams.
- Although the recent repair stopped the measurable leak, investigators still have not publicly confirmed the underlying root cause of the original cracks detected in 2019.
Background
The Zvezda module is one of the Russian-built core elements of the International Space Station and functions as a service module providing propulsion, guidance, and life-support connections. Launched in July 2000 on a Proton vehicle, Zvezda has operated in orbit for more than a quarter-century and has undergone multiple maintenance interventions over its lifetime. Crew and ground teams first noticed signs of a slow air leak in 2019; subsequent inspections found cracking or stress-related damage in the module’s structure that required repeated monitoring and partial containment measures.
Over the subsequent years, station crews tracked small but persistent pressure losses and implemented temporary countermeasures such as isolating suspect compartments and tightening seals. The problem drew attention because it involved long-serving hardware and because repairing pressurized modules in orbit is complex and risky. At the same time, the incident occurred against a backdrop of continued international cooperation on the ISS, where Russian-built systems remain deeply integrated with US and international modules and operations.
Main Event
In late 2025, station engineers executed a focused repair campaign aimed at the Zvezda module’s problem area. The on-orbit work combined crew-operated procedures with remote guidance from ground engineers in Roscosmos and NASA. Crews applied sealant and reinforced select fittings in the affected section; post-repair telemetry showed pressure stabilization and no further measurable air loss attributable to the previously active leak path.
The Zvezda repairs delivered an immediate operational relief: station environmental control systems returned to nominal margins without the need for repeated compensatory actions. Flight controllers continued to monitor for any residual seepage and ran a suite of diagnostic checks over multiple orbits to validate the repair under varying thermal and attitude conditions. Those checks produced consistent readings that matched pre-leak baseline levels.
Separately, a Soyuz launch in late November 2025 succeeded in placing its crew into orbit, but the launch caused damage on the ground when a large mobile platform beneath the rocket was not properly secured and collapsed into the flame trench. The incident took Site 31 at the Baikonur Cosmodrome in Kazakhstan temporarily offline and raised questions about pad readiness for near-term missions.
Despite the pad damage, updated internal schedules from NASA indicate planned Progress cargo flights on March 22 and April 26, 2026, and a Soyuz MS-29 crewed launch on July 14, 2026. Those dates signal agency-level confidence in repair timelines for the Baikonur pad infrastructure and in ongoing operational support for ISS manifest commitments.
Analysis & Implications
Stopping the Zvezda leak reduces immediate operational risk aboard the ISS and preserves the station’s integrated international cadence of crew rotations and cargo deliveries. For station life-support and mission planning, even a small persistent leak imposes workload and resource penalties; halting the leak restores margin to oxygen and CO2 control systems and reduces reliance on contingency resupply. The repair thus protects both crew safety and orbital logistics efficiency.
However, the underlying cause of the 2019 cracking remains unproven in public statements. Without a definitive root-cause finding, the fix should be viewed as a localized remediation rather than a systemic cure. Engineers will need continued structural assessments and possibly staged reinforcements to address material aging across other legacy Russian modules that share similar designs or manufacturing eras.
Politically and operationally, the episode highlights the interdependence of US and Russian space assets on the ISS. Successful cooperation on diagnostics and repairs is a practical goodwill outcome, but the Baikonur pad accident underscores vulnerabilities in launch infrastructure that can ripple into station scheduling. If pad repairs slip or new ground-system issues arise, it could force further schedule adjustments affecting both crewed and cargo missions.
Economically, protracted maintenance of aging components increases lifecycle costs for the ISS program and strengthens arguments for investing in newer modules or commercial solutions. For Roscosmos, demonstrating the ability to remediate long-standing problems could help sustain partner confidence; for NASA and international partners, it underscores the need for redundant logistics paths and contingency planning.
Comparison & Data
| Item | Date | Notes |
|---|---|---|
| Zvezda launch | July 2000 | Launched on Proton; primary Russian service module |
| Leak first detected | 2019 | Slow air loss attributed to structural cracking |
| Pad incident at Baikonur (Site 31) | Late November 2025 | Mobile platform fell into flame trench; pad offline |
| Progress cargo launches (planned) | March 22 & April 26, 2026 | NASA internal schedule entries |
| Soyuz MS-29 crew launch (planned) | July 14, 2026 | Will carry NASA astronaut Anil Menon |
The table above places the recent repair in a chronological context and shows how on-orbit hardware age (Zvezda at 25+ years) and ground infrastructure incidents (Baikonur pad damage) can combine to affect program schedules. Continued monitoring will focus on repeating diagnostics and confirming that the closed leak does not reappear under different thermal cycles or post-maneuver loads.
Reactions & Quotes
Roscosmos and NASA spokespeople provided measured responses emphasizing teamwork and ongoing verification. Their statements framed the repair as a technical achievement while noting further checks remain necessary.
“The immediate leak path has been sealed and system readings have normalized, but investigations into the root cause continue.”
Roscosmos (official)
Roscosmos framed the outcome as a technical success while acknowledging the investigation remains open. The agency emphasized that station safety protocols worked as designed and that crews were not endangered during repair operations.
“NASA continues to monitor the situation closely and remains confident in operational plans that include upcoming Progress and Soyuz missions.”
NASA (agency statement)
NASA’s comment accompanied updated internal scheduling that lists Progress flights in March and April 2026 and Soyuz MS-29 in July 2026; the agency characterized those dates as contingent on successful pad repairs and ongoing safety checks.
Unconfirmed
- No public confirmation yet that investigators have identified a single definitive root cause for the 2019 cracking; multiple hypotheses remain under review.
- The exact timeline and scope of repairs needed for Baikonur Site 31 to return fully to service have not been officially released beyond internal NASA schedule entries.
- It is not confirmed whether similar latent defects exist in other Russian-era modules without further intrusive inspections.
Bottom Line
The successful stopping of the Zvezda leak is a tangible operational win that reduces immediate risk aboard the ISS and buys time for longer-term assessments. It reflects effective international coordination in diagnosing and addressing a long-running technical problem on legacy hardware.
Nevertheless, the episode underlines that aging space infrastructure carries persistent risk: root-cause determinations are still pending, and ground-infrastructure incidents like the Baikonur pad collapse can create new schedule and safety challenges. Program managers and partners should treat the repair as a milestone, not the final resolution; continued vigilance, inspection, and investment will be necessary to sustain station operations through the coming years.
Sources
- Ars Technica article — media report summarizing repair and schedule details
- Roscosmos official site — Russian space agency official communications
- NASA (official) — agency schedules and program statements