Artemis II Launch Delayed to March 2026 Following Scrubbed Wet Dress Rehearsal

KENNEDY SPACE CENTER, Fla. — NASA has postponed the launch of Artemis II to no earlier than March 2026 after a persistent liquid hydrogen leak forced controllers to scrub a critical fueling test on Feb. 3. The delay marks a frustrating recurrence of the same technical gremlins that plagued the previous Artemis I campaign, underscoring the challenges of handling cryogenic propellants for the massive Space Launch System (SLS) rocket.

The issue arose during the mission’s "Wet Dress Rehearsal" (WDR), a rigorous practice run intended to simulate every phase of launch day up to engine ignition. While the launch team successfully loaded the rocket’s core and upper stages with over 700,000 gallons of super-cold propellants, the countdown was halted abruptly at T-minus 5 minutes and 15 seconds.

The "Pesky" Leak

According to Artemis Mission Manager Mike Sarafin, the scrub was triggered by a liquid hydrogen (LH2) leak at the Tail Service Mast Umbilical (TSMU). This component connects the mobile launcher tower to the base of the rocket's core stage, feeding it with propellant.

Sensors detected hydrogen concentrations exceeding the 4% safety limit near the quick-disconnect seal on the umbilical. Launch controllers attempted to troubleshoot the issue by stopping the flow of hydrogen and allowing the seal to warm up and "reseat"—a technique that has worked in the past—but the leak spiked again as the tank pressure increased for the terminal count.

“Hydrogen is the smallest molecule in the universe, and it is notoriously difficult to contain,” said John Honeycutt, SLS Program Manager, during a media briefing following the scrub. “We are dealing with a leak at a complex interface that must handle cryogenic temperatures of minus 423 degrees Fahrenheit while managing the thermal contraction of massive hardware.”

Proposed Fix and Schedule Impact

NASA is currently assessing whether the leak can be repaired at the launch pad. Engineers plan to access the TSMU plate to inspect the Teflon seal for microscopic debris or a misalignment. If the repair can be completed at Launch Complex 39B, the agency aims to conduct a second Wet Dress Rehearsal in late February, keeping a launch window open for early March.

However, if the repair requires a rollback to the Vehicle Assembly Building (VAB), the delay could extend significantly, potentially pushing the mission into April or May. For now, the agency has officially ruled out a February launch attempt.

A History of Hydrogen Headaches

The Feb. 3 scrub echoes the struggles of the Artemis I uncrewed test flight in 2022. That mission faced multiple delays over several months due to nearly identical hydrogen leaks at the same umbilical interface.

Following Artemis I, NASA implemented new loading procedures and hardware changes designed to mitigate "thermal shock" to the seals. While these changes were successful during initial tanking tests, the recurrence of the leak during the Artemis II WDR suggests that the TSMU interface remains a critical vulnerability in the SLS design.

The Stakes for Artemis II

Unlike its predecessor, Artemis II carries human crew. The mission will send NASA astronauts Reid Wiseman, Victor Glover, Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen on a 10-day journey around the Moon. It is the first crewed lunar mission since Apollo 17 in 1972.

The primary objective of Artemis II is not to land, but to validate the life support, communication, and manual piloting systems of the Orion spacecraft in deep space. A successful flight is the final prerequisite before Artemis III can attempt a crewed lunar landing.