I’ll be honest. I’m excited about this. Maybe it’s because I was a little kid when the last missions to the moon were taking place. I still remember seeing some of it on television, though I didn’t really understand what I was seeing.
The Artemis II mission will return four astronauts to the moon (though they won’t be landing) but there are some technical hoops to jump through first. Right now the rocket is going through a “wet dress rehearsal” where the cryogenically frozen propellant is loaded and a partial countdown takes place to make sure everything is behaving as it should.
Our “wet dress rehearsal” for Artemis II is underway at @NASAKennedy!
Watch our static feed as teams practice fueling the rocket and conduct a simulated launch countdown as we prepare for the real thing: https://t.co/4iEhNgfQb3
Real-time Artemis updates: https://t.co/40PMWktQjO pic.twitter.com/D9nZskFuP1— NASA (@NASA) February 2, 2026
Early on there were some troubles with leaks.
The hands-on test, called a “wet dress rehearsal,” involves filling up the rocket’s tanks with more than 700,000 gallons of super-chilled propellants.
A few hours into the test, NASA ran into issues with hydrogen leaks — a problem that also plagued the SLS rocket during its first round of dress rehearsals in 2022 ahead of the uncrewed Artemis I test flight. Ultimately, that mission took off about six months after NASA first attempted a wet dress rehearsal.
Kept at minus 423 degrees Fahrenheit, the liquified hydrogen, which is the primary fuel that powers the SLS rocket, is notoriously fickle because of its tiny molecular structure that makes the substance difficult to contain.
All told, the rehearsal is expected to include a run-through of the countdown on launch day — except that during the test run the clock will be halted with less than a minute to go.
The good news is that it appears they were able to deal with the leak problem and continued to top off the propellant tanks.
Teams had to stop loading LH2 into the SLS core stage twice to deal with leaks, but they managed to troubleshoot the issue in relatively short order and top up the rocket’s enormous tanks.
They got the tanks filled and then went into what they call “replenish mode” where the level of the tanks are maintained by adding small amounts of liquid propellant to counteract the amount that is boiling off inside the tanks.
NASA teams have transitioned all cryogenic tanks on the SLS (Space Launch System) rocket to replenish mode during the Artemis II wet dress rehearsal. This includes both liquid hydrogen and liquid oxygen tanks for the core stage and the interim cryogenic propulsion stage. Engineers continue to monitor liquid hydrogen concentration levels in the tail service mast umbilical, where a leak was previously detected. Levels are currently stable.
Teams enter replenish mode because cryogenic propellants naturally warm and evaporate over time, even in insulated tanks. Replenish counteracts this by continuously adding small amounts of liquid hydrogen and liquid oxygen to maintain proper levels and pressure. This ensures the rocket remains fully fueled and stable as the countdown progresses toward terminal count.
Finally, a crew will be helping to simulate putting the astronauts on board the spacecraft.
NASA’s Artemis II closeout crew and pad rescue team are en route to Launch Pad 39B. The closeout crew will head to the White Room inside the crew access arm on the mobile launcher and are responsible for securing the Orion spacecraft and ensuring all access points are properly configured before simulated crew ingress operations.
The White Room is the environmentally controlled area at the end of the crew access arm, providing a clean and safe space for astronauts to enter Orion on launch day. During the wet dress rehearsal, the closeout crew will close the spacecrafts’ hatches, verify hatch seals, check environmental conditions, and confirm all systems are ready for the next steps in the countdown.
all of this activity is going to continue for a few more hours and should end sometime after midnight. You never know what they’ll find later but at the moment it sounds like everything is working well enough that NASA could launch this as soon as Sunday.
Currently, NASA is targeting Feb. 8 for the liftoff of Artemis 2, which will send NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and Canada’s Jeremy Hansen on a 10-day trip around the moon. But that’s contingent upon a successful wet dress, as well as a number of other factors — good weather conditions, for example.
NASA will be holding a press conference tomorrow at noon to let us know whether the weekend launch is still possible or if they discovered some other issue that needs to be fixed before that can happen. Look for an update on the site tomorrow.
Artemis II Wet Dress Rehearsal: Crew module hatch preparations and closure.
This step simulates launch day procedures, ensuring the spacecraft is sealed and ready for crew to enter Orion for launch. The Artemis II astronauts are not participating in the rehearsal.
Milestones… pic.twitter.com/1pXdPqNtVe
— NASA’s Kennedy Space Center (@NASAKennedy) February 3, 2026
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