Hydrogen Leak Delays NASA Artemis II Moon Mission

NASA’s highly anticipated Artemis II mission, set to mark humanity’s return to lunar orbit after more than half a century, has hit another speed bump. On Monday, February 2, 2026, engineers at Kennedy Space Center in Florida detected hydrogen leaks during a critical fueling test—known as the Wet Dress Rehearsal (WDR)—forcing the agency to postpone the launch by at least a month. This latest setback means the earliest possible launch date for Artemis II is now March 6, 2026, with further delays possible if issues persist.

The WDR is designed to simulate every step of launch day, from loading more than 700,000 gallons of super-chilled cryogenic propellant into the Space Launch System (SLS) rocket to practicing countdown procedures and safely removing fuel in the event of an abort. According to NASA’s official statement, "Engineers pushed through several challenges during the two-day test and met many of the planned objectives." But the most pressing objective—proving the SLS can be safely fueled and readied for launch—was thwarted by a recurring leak at the interface between the rocket and its launch platform.

"Teams have stopped the flow of liquid hydrogen through the tail service mast umbilical interface into the core stage after leak concentrations exceeded allowable limits," NASA reported on Monday afternoon. The agency explained that after pausing to troubleshoot, engineers attempted to resume fueling, but "initial steps to correct the leak proved unsuccessful. The leak rate at the interface of the tail service mast umbilical continues to exceed the allowable limits. Liquid hydrogen filling operations on both the core stage and upper stage are paused as the team meets to determine next steps."

This isn’t the first time hydrogen leaks have upended Artemis program schedules. Back in 2022, similar leaks delayed Artemis I, the uncrewed precursor to Artemis II, by several months. Engineers eventually overcame the problem by revising hydrogen loading procedures, but the recurrence of leaks in the same area has raised eyebrows and concerns. "With more than three years between SLS launches, we fully anticipated encountering challenges," NASA Administrator Jared Isaacman wrote on X (formerly Twitter). "That is precisely why we conduct a wet dress rehearsal. These tests are designed to surface issues before flight and set up launch day with the highest probability of success."

The Artemis II WDR, which began around 12:30 p.m. ET on Monday and stretched into the early hours of Tuesday, was halted with about five minutes and 15 seconds remaining on the countdown clock. The automated ground launch sequencer stopped the proceedings after detecting a spike in the hydrogen leak rate. According to NBC News, liquid oxygen continued to flow into the SLS core stage, and hydrogen continued into the upper stage, but the persistent leak at the tail service mast umbilical interface could not be safely ignored.

Complicating matters further, NASA teams faced additional challenges during the test. There were delays in preparing the Orion spacecraft, intermittent audio dropouts in ground communications, and cold weather that affected some of the launch pad cameras. Despite these headaches, NASA did manage to fill all core stage and interim cryogenic propulsion stage tanks, and the updated Orion closeout purge procedures—which are vital for crew safety—were successfully demonstrated.

With the launch now delayed until at least March, the four astronauts selected for Artemis II—NASA’s Commander Gregory Reid Wiseman, pilot Victor Glover, mission specialist Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen—have been released from quarantine. The crew had been scheduled to arrive at Kennedy Space Center on the afternoon of February 3, but with the revised timeline, they won’t travel to Florida until about 10 days before the new launch date. NASA said the astronauts will re-enter quarantine roughly two weeks before the next targeted launch opportunity, a precaution to minimize the risk of illness before such a high-profile mission.

Artemis II represents a major milestone for NASA and its international partners. It will be the first time since Apollo 17 in 1972 that astronauts travel beyond low Earth orbit. The mission is designed as a lunar flyby: the Orion spacecraft will loop around the far side of the Moon before returning to Earth, paving the way for subsequent Artemis missions that aim to land humans at the Moon’s south pole. This is the first time both the SLS rocket and Orion capsule will carry humans, raising the stakes considerably. As NASA Administrator Isaacman emphasized, "As always, safety remains our top priority, for our astronauts, our workforce, our systems, and the public. We will only launch when we believe we are as ready to undertake this historic mission."

The timing of Artemis II is tightly linked to the Moon’s orbit. Each month provides only a handful of launch windows when the Moon is in the right position to allow Orion to follow a free return trajectory—a path that lets the spacecraft safely loop around the Moon and return to Earth in case of an emergency. NASA has identified opportunities from March 6 through March 9, and on March 11, with additional dates in April if needed. According to Space.com, missing one window could mean waiting several weeks for the next viable opportunity.

For NASA, the recurring hydrogen leaks are a stark reminder of the challenges inherent in launching such a massive and complex vehicle. The SLS rocket, standing more than 320 feet tall and generating 8.8 million pounds of thrust at liftoff, is the most powerful rocket NASA has ever built. Its reliance on liquid hydrogen and liquid oxygen—fuels that must be kept at temperatures below minus 400 degrees Fahrenheit—makes fueling operations especially tricky. Even tiny imperfections in seals or fittings can allow hydrogen, the smallest and lightest molecule, to escape.

The Artemis program is central to NASA’s goal of returning humans to the Moon and, eventually, sending astronauts to Mars. Artemis I, the uncrewed test flight in 2022, successfully circled the Moon and returned to Earth, but not before its own series of delays and technical hiccups. The lessons learned from Artemis I and now Artemis II are shaping NASA’s approach to risk and readiness as the agency prepares for increasingly ambitious missions.

NASA officials have scheduled a briefing to discuss the early results from the wet dress rehearsal and outline steps for addressing the hydrogen leak. While the agency remains optimistic about resolving the issue, the repeated leaks have sparked calls for more thorough reviews and perhaps even design changes to the SLS’s ground support equipment. For now, the Artemis II astronauts and the world must wait as NASA’s engineers work to ensure that when the countdown finally reaches zero, the mission will proceed as safely as possible.

The road to the Moon has always been fraught with challenges, and Artemis II is no exception. But with every test and every delay, NASA edges closer to sending humanity back to our celestial neighbor, determined to make sure that when launch day finally arrives, the mission will soar.