NASA Confirming Success of ISS Leak Repairs Before Finalizing Ax-4 Launch Date

NASA, SpaceX and Axiom Space are looking at Thursday, June 19, for the launch of Axiom-4 as NASA continues to evaluate the apparent success of recent repairs in the Russian segment of the International Space Station. A tunnel leading to a docking port at the far end of the Russian segment has experienced air leaks for several years and defied previous remedies, but the tunnel now is holding pressure. NASA wants a few more tests before docking another spacecraft, however, and on Thursday abruptly postponed the launch of Ax-4. NASA said they now are “reviewing launch opportunities” and June 19 is the earliest.

NASA provided limited information about the last minute decision on June 12 to delay the launch, which is taking four private astronauts to the ISS on a 14-day mission.

The crew is launching in a SpaceX Crew Dragon spacecraft atop a SpaceX Falcon 9 rocket.  SpaceX delayed the launch from June 10 to June 11 because of weather and again on June 11 because it needed to repair a liquid oxygen (LOX) leak on the rocket. By Thursday afternoon, June 12, they’d fixed the leak, successfully completed a wet dress rehearsal test, and were waiting to set a new launch date.

Falcon 9 wet dress rehearsal complete. We’ll continue to work closely with @NASA and @Axiom_Space to determine the best launch opportunity for Dragon and the Ax-4 crew to the @Space_Station

— SpaceX (@SpaceX) June 12, 2025

NASA then suddenly announced they were postponing the launch in order to “understand a new pressure signature” in the Russian tunnel even though it “now is holding pressure” after recent repairs.

The statement seemed self-contradictory. The problem was that the tunnel hadn’t been able to hold pressure, but now it could, yet the launch was postponed. NASA soon sent out a brief reassurance via email to reporters that the ISS crew was fine and normal operations continued.

“The crew aboard the International Space Station is safely conducting normal operations. We’re assessing this latest update and will provide additional information as available.”  — NASA statement, June 12, 2025, 5:08 pm ET

The agency declined to comment yesterday, but this morning offered a bit more of an explanation on the ISS blog. Even though the tunnel now is holding pressure, they want to make sure that’s because the leaks are sealed and not because “of a small amount of air flowing into the transfer tunnel across the hatch seal from the main part of the space station.”

The 420 Metric Ton ISS is composed of two interdependent sections, the U.S. segment and the Russian segment.  The problematic tunnel, PrK, is to a docking port for Russian cargo vehicles at the far end of Russia’s Zvezda Service Module (shown in red in the illustration below). Air leaks were first detected in the PrK in September 2019. Attempts to plug them over the years yielded mixed results.

The ISS is old. The first modules, Zarya and Node 1 (Unity), were launched in 1998.  Zvezda docked in July 2000 and the ISS has been permanently occupied by crews rotating on roughly 6 month schedules since November 2000.

Bob Cabana, a former NASA astronaut who commanded the first mission to the ISS in 1998 and later was Director of Kennedy Space Center and NASA Associate Administrator, retired from NASA at the end of 2023 and now chairs the NASA ISS Advisory Committee. The committee meets twice a year with its Roscosmos counterpart. Collectively they are the U.S.-Russian Joint Commission.

He reported in November 2024 and April 2025 that Russian and American technical experts disagree on the underlying cause and seriousness of the leaks. The American side is more deeply concerned, but both are committed to keeping the ISS operating until 2030 as long as it is safe to do so. Canada, Japan and 11 European countries working through the European Space Agency are the other ISS partners.  All except Russia formally agreed to operating the ISS until 2030, after which it will be intentionally deorbited into the Pacific Ocean. Russia is committed only until 2028, but NASA expects it will extend that to 2030 in due course.

The question is whether the ISS will make it that long.  If the repairs to the tunnel are in fact successful, that will be good news from a technical standpoint.

Another threat to the ISS right now, however, is U.S. budget cuts. The Trump Administration wants to reduce funding and the number of crew and cargo flights to the ISS, as well as limiting research to only what’s needed for sending humans to the Moon and Mars, as part of its proposed FY2026 $6 billion cut to NASA’s budget.

NASA ISS Program Manager Dana Weigel said at a May 20 Ax-4 overview briefing that she already is looking at reducing the number of crew on each flight from four to three because of FY2025 funding constraints that are limiting the number of cargo flights needed to resupply food and other essentials.

Meanwhile, Elon Musk, founder and CEO of SpaceX, twice has promoted the idea of ending operations two years from now instead of in 2030 despite the billions SpaceX earns by launching cargo and crews.  His most recent post about this yesterday asserted that he has “serious concerns” about its long-term safety.

NASA awarded SpaceX an $843 million contract to build a U.S. Deorbit Vehicle (USDV) to propel the ISS from orbit into the Pacific to be ready for launch by 2029. The plan is to have it docked to the ISS for about a year as the orbit gradually lowers, with reentry in 2030. Musk hasn’t said how much earlier the USDV could be available.

By contrast, Sen. Ted Cruz (R-TX), chair of the Senate Commerce, Science, and Transportation Committee that oversees NASA, is proposing to add $1.25 billion for the ISS in the reconciliation package. Congress has been unwavering in its bipartisan determination to ensure there is no gap between ISS and the commercial space stations intended to succeed it — Commercial LEO Destinations (CLDs). Congress wants to ensure NASA can continue to conduct microgravity research to support its objectives and that China is not the only country with an Earth-orbiting space station. China’s Tiangong-3 space station has been operational since 2021, permanently occupied since 2022, and they are getting ready to expand it.

Cruz would also add $325 million for the USDV, but doesn’t specify what it’s for. The contract doesn’t include launch or integration onto the launch vehicle. Former NASA Administrator Bill Nelson told Congress last year he needed $1.5 billion for the USDV and Ken Bowersox, the head of NASA’s Space Operations Mission Directorate, warned that if Congress didn’t appropriate sufficient funds they would have to take it from other parts of the ISS budget.

Whatever the ISS’s future holds, right now the Axiom-4 crew is awaiting launch. That could happen as soon as Thursday.

Axiom has its own space station plans, too. It’s one of three companies receiving funding from NASA to facilitate the development of commercial space stations to succeed ISS. Several others have unfunded arrangements. Unlike the others, Axiom’s design relies on attaching its first module to the ISS. Axiom’s Allen Flynt said at a June 9 Ax-4 pre-launch briefing that’s now planned for 2027. The original date was 2024.

Of all the U.S. companies working on commercial space stations, Vast is saying it will be ready first, with launch of Haven-1 planned for May 2026 although it has limited capabilities. Haven-1 can accommodate four astronauts for two weeks.  A more capable version with multiple modules, Haven-2, is planned for first launch in 2028 and completion in 2032. Vast has an unfunded agreement with NASA.  The company is using SpaceX for launch, crew transportation, crew training, and communications via Starlink.

 

This article has been updated.