Artemis II Launch Date Updates: New Dates Announced After Wet Dress Rehearsal
If you’ve been counting down the days to Artemis II, you’re not alone. Here at The Space Store, we’ve been eagerly awaiting humanity’s return to lunar orbit, and now we have some updates to share.
After a February wet dress rehearsal encountered a hydrogen leak, NASA has pushed the launch window to March 2026, with specific dates now targeted for March 6-9 and March 11. Backup opportunities extend into April, with windows on April 1, April 3-6, and April 30.
The wet dress rehearsal (WDR) is a critical pre-launch test that simulates launch day conditions, including fully fueling the rocket. For Artemis II, this was the first time the powered-up, integrated, and fueled stack could communicate with NASA’s systems.
By all accounts, things were progressing smoothly. The Orion spacecraft was configured for flight, the closeout crew had safely sealed the hatches and white room, and the access arm bridge had retracted without issue. The rocket was fully fueled with liquid hydrogen and liquid oxygen.
As the team entered the terminal countdown and began pressurizing the core stage, however, a hydrogen leak at the tail service mast umbilical (TSMU) cavity spiked to cutoff limits. The leak occurred at the base of the rocket, specifically where the flight and ground plates come together.
During the slow-fill phase, everything had looked fine. But as pressure gradually increased during fast-fill, the leak emerged. NASA maintains a leak limit cutoff of 16% for the Space Launch System (SLS), and during the WDR, the leak ranged from 12-14%. When the terminal count began and core stage pressurization increased, the leak quickly exceeded acceptable levels, forcing NASA to halt the countdown.
What made this happen?
The flight-side interface where the leak occurred is complex and highly sensitive to flow rates and pressures. It uses a pressure-assisted seal that can be affected by various factors.
NASA’s mission leadership believes there may be a misalignment, deformation, or debris on the seal. The team is currently reviewing data to determine which bleed line is involved, and workers will access the interface plate to remove and inspect the seal.
NASA suspects that the rollout process itself may be a contributing factor. The TSMU is mated to the rocket stack during rollout from the Vehicle Assembly Building to the launch pad. Engineers can’t fully characterize the stresses experienced throughout the entire vehicle during these delicate moves the same way they can predict stresses while on the pad. This is one reason why NASA never wants to move the rocket unless absolutely necessary.
It’s worth noting that similar hydrogen leaks plagued Artemis I, though those occurred on the ground-side of the interface. After that mission, engineers made numerous modifications and improvements, and importantly, no leak occurred on the ground-side during the Artemis II wet dress rehearsal.
As John Honeycutt, chair of the Mission’s Management Team, explained during a February 3 news conference: “After Artemis I, with the challenges we had with the leaks, we took a pretty aggressive approach to do some component-level testing with some of these valves and the seals, to understand their behavior. We got a good handle on that relative to how we install the flight-side and the ground-side interface, but on the ground, we’re pretty limited in how much realism we can put into the test. We try to test like we fly, but this is a very complex interface. When you’re dealing with hydrogen, it’s a small molecule. It’s highly energetic.”
The good news is that NASA believes the leak can be fixed at the pad, so no rollback to the Vehicle Assembly Building is currently planned. The team already has experience managing similar issues from Artemis I, where they learned to let the seal and interface warm up and adjust pressure to stay within leak limits while filling the tank.
Artemis II can remain on the pad through March. Beyond that timeframe, a rollback to the VAB would be necessary so technicians can service the upper stage batteries. However, there’s plenty of margin on other components. The solid rocket boosters are certified through 2028, and Orion’s CO2 scrubbing system is checked out to mid-2027.
NASA will conduct another wet dress rehearsal before launch. During this next test, the team hopes to accomplish two objectives they couldn’t complete in February: verifying a 3-minute hold capability (demonstrating that the SLS cryogenic propellant systems can hold in a launch-ready state) and executing a recycle demonstration where they simulate a cutoff in the countdown and come back to target a new T-0.
Identifying and addressing issues before they become problems on launch day is exactly what tests like these are meant to accomplish. All things considered, this was a positive outcome.
Gear Up for Launch Day
Want to commemorate this exciting mission? The Space Store has you covered with official NASA Artemis II merchandise, including apparel, accessories, and drinkware.
Includes crew member names: Reid Wiseman; Victor Glover; Christina Koch; Jeremy Hansen
Pre-shrunk cotton, available in 3 colors.
This white glossy mug is perfect for whatever you’re drinking. Lead and BPA-free ceramic, and made-to-order.
Check out our whole collection of Artemis II merchandise at The Space Store and stay tuned for more updates as NASA works toward that March launch window. History is just around the corner.
-Written by Matt Herr