When NASA wrapped up the first Artemis II wet dress rehearsal on February 3 at Kennedy Space Center, they had successfully filled the SLS rocket’s tanks with cryogenic propellant. That was the good news, but the less welcome bad news was that the test revealed higher-than-allowable hydrogen gas leaks at the Tail Service Mast Unit on the launch pad. Obviously, those leaks must be repaired before a launch attempt.
NASA Stream from the first Wet Dress Rehearsal indicated full LH2 and LOX tanks on SLS. Credit: NASA
The Work For WDR-2 Started As Soon As WDR-1 Was Completed
Not long after propellant draining was complete after WDR-1, technicians began working to access the TSMU umbilical. They detached both the rocket-side and ground-side interface plates to inspect the area where elevated hydrogen levels were detected, and replaced seals around two fueling lines.
The two tail service masts — each about three stories tall — provide the cryogenic propellant lines and electrical cable connections to the SLS core stage. They tilt back before launch and include “quick disconnects” — mechanisms that instantaneously detach at liftoff to ensure safe retraction.
Reconnecting the interfaces is expected to be complete by Monday, Feb. 9. Engineers are still evaluating the root cause of the leak, and the removed seals are being analyzed. NASA also plans additional testing at Stennis Space Center in Bay St. Louis, Mississippi, to evaluate the dynamics of the interface plates. Engineers are reviewing options to verify the repair before committing to the next full wet dress rehearsal.
Repairs For WDR-2
Here’s a breakdown of the repairs underway and the operational changes NASA is making for WDR-2:
Five Key Changes for the Next Rehearsal
Five Key Changes for the Next Rehearsal
Artemis II Wet Dress Rehearsal | Kennedy Space Center
Type
Change
Details
Hardware Fix
Two seals replaced
Seals replaced around fueling lines at the tail service mast umbilical where hydrogen concentrations exceeded allowable levels. Removed seals are being analyzed and additional plate dynamics testing is planned at Stennis.
Operations
Orion hatch closed before test
The crew module hatch will be sealed prior to the rehearsal. The closeout crew — who on launch day help astronauts into their seats and close both Orion hatches — will not be deployed to the pad.
Operations
Crew access arm stays extended
The arm will not be retracted during the next rehearsal. Engineers successfully demonstrated during the Feb. 3 test that the ground launch sequencer can retract it during the final countdown phase, so that objective is already complete.
Timeline
One extra hour in countdown
NASA has added 30 minutes of extra hold time at each of two planned holds — one before and one after tanking operations — to allow more time for troubleshooting. The total countdown is now one hour longer. This does not affect the crew’s launch-day timeline.
Focus Shift
Rehearsal focused on fueling
With the crew access arm retraction and other pad objectives already demonstrated, the next WDR will concentrate on tanking operations and verifying the hydrogen leak repair.
NASA continues to eye March as the next potential launch opportunity but will not set a targeted launch date until after completing a successful wet dress rehearsal and reviewing the data. The critical second WDR is set to start as soon as this Friday, February 13th.
Artemis II at LC-39B on February 1, 2026 Photo: Charles Boyer
Teams at Kennedy Space Center conducted and mostly completed a critical Wet Dress Rehearsal for the launch of the Artemis II rocket and ground support teams yesterday. The test was not without problems: Hydrogen leaks at the tail mast area of the pad and an issue closing Orion’s hatches bedeviled the tests, resulting in NASA announcing that the launch of the Artemis II mission is now no earlier than March 6, 2026.
“The Artemis II wet dress rehearsal countdown was terminated at the T-5:15 minute mark due to a liquid hydrogen leak at the interface of the tail service mast umbilical, which had experienced high concentrations of liquid hydrogen earlier in the countdown, as well,” NASA said.
A view of the Tail Mast and the retractable Liquid Hydrogen feed lines for SLS. Photo: NASA
In a press conference today, Artemis II Launch Director Charlie Blackwell-Thompson said, “When we got into the LH2 fast fill—which was around 12:29—is when we picked up our first leak in the SMU, in the cavity, which is where the flight and the ground plate come together. It’s that cavity in between. It’s in our eight-inch fill and drain line there. We have a QD that connects those two together.”
Charlie Blackwell-Thompson in today’s NASA press conference. Via NASA livestream
“It was similar to some of the signatures we saw during Artemis I. Our leak rate was a little bit higher—somewhere around 12 to 14%,” Blackwell-Thompson continued. “We tried a contingency procedure that we used during Artemis I: you let that QD warm up, you let the seal warm up, and you try it again. We did that a couple of times, worked our way through it, and were able to load the core stage all the way to replenish.”
When asked what items were missed in the Wet Dress Rehearsal, Blackwell-Thompson said, “What we didn’t get to do: we wanted to get through terminal count. We wanted to get inside terminal count, hold, and verify our three-minute hold capability—tanks in launch-ready state and you can hold them for up to three minutes.”
“We also wanted to demonstrate a recycle: come down, have a planned cutoff, come back and retarget a new T-0 within the launch window. Didn’t get a chance to do that.”
What’s Next
Before the March window, NASA’s engineers and mission managers will review data, equipment and procedures from the WDR yesterday and they will conduct a second Wet Dress Rehearsal before committing to a launch date. Of key interest are the Tail Mast interfaces that deliver LH2 to the rocket’s propellant tanks.
“With the conclusion of the wet dress rehearsal today, we are moving off the February launch window and targeting March for the earliest possible launch of Artemis II,” NASA Administrator Jared Isaacman said today. “With more than three years between SLS launches, we fully anticipated encountering challenges. 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.”
Remaining Launch Windows
ARTEMIS II MISSION AVAILABILITY – SPRING 2026
(Subject to Adjustments)
March 2026
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April 2026
Mon
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Launch Window Available
Launch Window Opening
Window
Date
Local Time
UTC
Lighting
Mins
Mar 6
8:29 PM EST
Mar 7, 01:29
2.05 hrs after sunset
120
Mar 7
8:57 PM EST
Mar 8, 01:57
2.51 hrs after sunset
120
Mar 8
10:56 PM EDT
Mar 9, 02:56
3.48 hrs after sunset
120
Mar 9
11:52 PM EDT
Mar 10, 03:52
4.40 hrs after sunset
120
Mar 10
12:48 AM EDT
Mar 10, 04:48
5.36 hrs after sunset
115
Apr 1
6:24 PM EDT
Apr 1, 22:24
1.28 hrs before sunset
120
Apr 3
8:00 PM EDT
Apr 4, 00:00
0.30 hrs after sunset
120
Apr 4
8:53 PM EDT
Apr 5, 00:53
1.17 hrs after sunset
120
Apr 5
9:40 PM EDT
Apr 6, 01:40
1.95 hrs after sunset
120
Apr 6
10:36 PM EDT
Apr 7, 02:36
2.87 hrs after sunset
120
Apr 30
6:06 PM EDT
Apr 30, 22:06
1.86 hrs before sunset
120
↔ Scroll table on mobile
As of: February 3, 2026 at 8:32 AM EST
The Good and The Bad
A liquid hydrogen leak at the LC-39B’s Tail Mast umbilical connection to SLS’s core stage forced engineers into a troubleshooting effort that pushed the countdown about two hours behind schedule. The team cycled through several repair attempts, first halting LH2 flow, then letting the interface warm so seals could seat themselves properly, and finally by tweaking propellant flow rates before pressing ahead. Ultimately, they were successful in their efforts and got the 322-foot tall rocket fully fueled, but a great deal of time was lost during the effort.
NASA graphic from their livestream indicated that SLS was fully loaded with propellant by 5:45 PM ET
Secondly, a recently replaced valve tied to Orion’s crew hatch pressurization system needed to be retorqued, and closeout work ran longer than expected. NASA stated around 10 PM last night that, “The closeout crew remains in the White Room and has closed the Orion spacecraft’s crew module hatch. While performing seal pressurization checks on the counterbalance assembly, which could be used to help open the hatch, a valve associated with Orion’s hatch pressurization was inadvertently vented. The counterbalance assembly then needed to be repressurized to allow work to continue.”
Finally, communications issues from SLS to ground caused some issues and will need to be remediated prior to the next Wet Dress Rehearsal, much less any launch attempt in March.
Clearly, there’s some work to do before Artemis II will be ready to fly.
The Artemis II crew has been released from quarantine for the time being. Once a new potential launch date becomes clearer, they will return to quarantine and fly to Kennedy Space Center for final preparations prior to launch.
NASA has scheduled a 1 PM ET press conference to offer more details.
Artemis-1 on the launch pad at LC-39B at Kennedy Space Center in 2022. Photo: Charles Boyer
NASA announced today that the Artemis program has encountered new delays, causing a shift in the timeline of planned launches.
Artemis II is now slated for September 2025, with Artemis III now slated for September 2026 according to NASA Administrator Bill Nelson in a news conference held this afternoon. Artemis IV, the first mission to the Gateway lunar space station, remains on track for 2028. “As I continue to say, we will launch when are ready,” said NASA Associate Administrator Jim Free. Free is the third highest-ranking executive and highest-ranking civil servant. He is the senior advisor to NASA.
Originally slated for late 2024, Artemis II has been delayed due to technical issues that have cropped up in the program since the Artemis I launch in 2022. Those issues range from problems encountered with batteries for the Orion capsule during testing. Artemis III, the planned landing on the moon has also encountered delays as SpaceX works on its Starship Heavy launcher and with it the human lander needed to touch down on the lunar surface.
Artemis II
Rumors had been floating around in the space industry that NASA might choose to repeat the Artemis I mission with Artemis II, but the agency made it clear today that Artemis II will remain “the first crewed Artemis mission around the Moon.”
“[Artemis I] was so successful that additional tests were added in the course [of the mission],” remarked NASA Administrator Bill Nelson. Prior to launching, it must first solve some technical issues that have arisen since Artemis I splashed down in the Pacific Ocean near California on December 11, 2022.
Artemis II crew members, shown inside the Neil Armstrong Operations and Checkout Building at NASA’s Kennedy Space Center in Florida, check out their Orion crew module on Aug. 8, 2023. From left are: Victor Glover, pilot; Reid Wiseman, commander; Christina Hammock Koch, mission specialist; and Jeremy Hansen, mission specialist. Photo: NASA
Heat Shield
The Orion capsule experienced unexpected loss of char layer pieces during the re-entry phase of the Artemis I mission, prompting NASA and prime Orion contractor Lockheed Martin to open an investigation into the issue to find the root cause of the unexpected material loss, as well as develop plans to fix it.
Amit Kshatriya, deputy associate administrator, Moon to Mars Program, Exploration Systems Development Mission Directorate. Photo: NASA
“From the test flight, we found one item that we need a little more time to work, and that is the thermal protection system on the […] heat shield,” said Amit Kshatriya, deputy associate administrator, Moon to Mars Program, Exploration Systems Development Mission Directorate in today’s media conference.
Inside the Neil Armstrong Operations and Checkout Building high bay at NASA’s Kennedy Space Center in Florida, the AVCOAT block bonding is complete on the Artemis II heat shield on July 2, 2020. Photo: NASA
Kshatriya continued that the review is going “quite well” but NASA wants to assemble the data and understand it quite well before the Artemis II flight. “Before we attempty re-entry from a circumlunar mission like we’ll have from Artemis II that we’re 100% confident that we understand under those conditions.”
Orion Life Support System
“During the acceptance of some components for Artemis III we noticed a failure in some motor valve circuitry that was driving valves on the spacecraft itself,” said Kshatriya. “These components passed testing for Artemis II but did not for Artemis III. That gave us pause and caused us to examine that circuit in a more detailed way. When we examined it, we learned that there was a design flaw in that circuit. Those valve electronics affect many parts of the life support system in the spacecraft, in particular the CO2 scrubbing system. Once we recognized the design flaw […] it became very clear to us that it was unacceptable to accept that hardware and we have to replace it in order to guarantee the safety of the crew.”
“The way to replace that given the current configuration of the spacecraft, the access to those components, the access to those bays is going to take us quite a bit of time to get to,” Kshatriya continued. “Every connector that we touch as part of that replacement operation will have to be tested after we’re done and we’ll have to put the vehicle through functional testing afterwards. We know how to fix it,” Kshatriya said. “We just need to make sure that we take the time to do it according to the workmanship standards that we expect for a human-rated vehicle.”
Launch Tower
NASA has a new launch tower that they plan to use for the next Artemis mission. The 380-foot tall (115 meters) tower connects to NASA’s Space Launch System (SLS), which is set to launch the Artemis II crew of four astronauts around the moon.
Launch Pad 39B at NASA’s Kennedy Space Center on Aug. 17, 2023. Photo: NASA
NASA’s Exploration Ground Systems team has been performing tests and applying upgrades for the new tower. They recently conducted a launch day demonstration for the Artemis II crew of NASA astronauts Reid Wiseman, Victor Glover, Christina Koch and Canadian astronaut Jeremy Hansen.
“There are new capabilities being on-ramped for the mission,” said Kshatriya. “We have new facilities at KSC to enable rapid turnaround for propellant loading, as well as [new capabilities] for the loading of the crew and the egress of the crew.”
New Abort System
The test version of Orion attached to the Launch Abort System for the Ascent Abort-2. This system will be upgraded prior to Artemis II. Photo: NASA
“For the launch vehicle, we have a new abort system that will be activated in an integrated way across the stack and of course with the spacecraft, we have a new life-support system and its ability to respond to those aborts. Those are all added, and of course those will support the crew and to support crew safety,” Kshatriya said.
“We’ve qualified Orion to survive [the abort environment.] We have, however, as part of that qualification campaign found a few cases where we believe there could be some deficiencies in the performance of the electrical system in particular some of the batteries that we need to make sure we understand how they are enduring those environments.”
“We’re still very early in that investigation. We’ve not yet developed a forward path. Multiple parallel options [exist] to fix this issue,” said Kshatriya. He added that “We also have a lot of options to determine whether or not we believe those environments are accurate and we have a lot of testing to do, and we wanted to make sure we gave ourselves the time to do that. Crew safety is going to drive our decision making there.”
NASA did not comment about any new in-flight abort systems test in today’s teleconference.
While these delays may be frustrating to the public, perhaps NASA Administrator Bill Nelson put it best today when he echoed Jim Free by saying that “we’ll fly when we are ready to fly.”
For the space agency crew safety is the first priority followed by mission assurance. The simple truth is that not many people will remember the delays five years in the future, but no one would ever forget a disaster. NASA has made mistakes rushing launches in the past and it is showing a dogged determination to not the repeat those mistakes again. That’s as it should be, not only for NASA, for America and for space exploration, but also to the crew of the Artemis missions and their families.
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