WDR

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

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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.

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Artemis II stands tall in the chilly air on February 1st, 2026
Photo: Charles Boyer

The countdown for the Artemis II Wet Dress Rehearsal is underway at Kennedy Space Center. Yesterday at 8:13 PM ET, or L-48:40 hours, the simulated countdown began in preparation for a test launch window opening at 9 PM tomorrow, February 2nd.

Artemis II will not launch during this countdown, of course, as it is just a test countdown. The Artemis II crew will not be aboard during Orion the WDR.

Sometime around 1 AM ET Tuesday, or February 3rd, the WDR will conclude.

What Comes After The WDR

After the test cycle concludes, engineers and mission managers will review data gathered during the Wet Dress Rehearsal. This process may take a few days as each major system is reviewed. Since Artemis I, NASA has implemented changes to the liquid Hydrogen systems at LC-39B. That will be a particular area of concern, as H2 leaks bedeviled the Artemis I countdowns both in WDR and later on the night it launched.

After the Data Review, a Flight Readiness Review can be held, during which all aspects of the mission are reviewed: the SLS rocket, the Orion spacecraft, ground systems at the Cape, and the status of the recovery teams that would be first responders to a major anomaly, should one occur, and many others.

The FRR is last major review for the flight, and in it, the Artemis II management team will need to give the mission permission to proceed towards a launch. Only after that milestone is achieved will a launch date and time be announced by NASA.

Artemis II on the launch mount at LC-39B at Kennedy Space Center
Photo: Charles Boyer

The Wet Dress Rehearsal In Detail

L-49 Hours, 15 Minutes and Counting
TimeActivity
L-49H 15M Launch team arrives on stations; countdown begins
L-48H 40M Countdown clock begins
L-48H 45M – L-39H 45M LOX/LH2 system preparations for vehicle loading
L-47H 30M – L-38H 30M Fill water tank for sound suppression system
L-40H 30M – L-39H Interim Cryogenic Propulsion Stage (ICPS) powered up
L-39H 30M – L-38H 45M Core stage powered up
L-38H 45M – L-34H 30M Final preparations of four RS-25 engines
L-34 Hours, 30 Minutes and Counting
TimeActivity
L-33H 45M – L-33H 10M ICPS powered down
L-32H 30M – L-28H 30M Charge Orion flight batteries to 100%
L-30H 30M – L-23H 30M Charge core stage flight batteries
L-19H 30M – L-16H Orion crew suit regulator leak checks
L-19H 15M – L-17H 45M ICPS powered up for launch
L-15 Hours and Counting
TimeActivity
L-14H 30M – L-13H All non-essential personnel leave Launch Complex 39B
L-13H 15M – L-11H 05M Air-to-GN2 changeover and vehicle cavity inerting
L-12H 45M – L-11H 15M Ground Launch Sequencer (GLS) activation
L-11 Hours, 40 Minutes and Counting
TimeActivity
L-11H 35M – L-9H 20M Built-in hold: 2 hours, 15 minutes
L-11H 40M – L-10H 30M Weather and tanking briefing
L-10H 20M Go/No-Go decision to begin tanking
L-10H 20M – L-9H Orion cold soak
L-10H 10M – L-9H 50M Core stage LOX transfer line chilldown
L-10H 10M – L-9H 25M Core stage LH2 chilldown
L-10 Hours and Counting
TimeActivity
L-9H 50M – L-9H 10M Core stage LOX main propulsion system chilldown
L-9H 25M – L-9H Core stage LH2 slow fill start
L-9H 20M Resume T-Clock from T-8H 10M
L-9H 10M – L-8H 55M Core stage LOX slow fill
L-9H – L-7H 40M Core stage LH2 fast fill
L-8H 55M – L-6H 10M Core stage LOX fast fill
L-8H 45M – L-8H 10M ICPS LH2 chilldown
L-8H 10M – L-7H 25M ICPS LH2 fast fill start
L-7H 45M – L-6H ICPS LOX main propulsion system chilldown
L-7H 40M – L-7H 30M Core stage LH2 topping
L-7H 30M – terminal Core stage LH2 replenish
L-7H 25M – L-7H 05M ICPS LH2 vent and relief test
L-7H 05M – L-6H 55M ICPS LH2 tank topping start
L-6H 50M – terminal ICPS LH2 replenish
L-6H 10M – L-5H 40M Orion communications system activated (RF to Mission Control)
L-6H 10M – L-5H 40M Core stage LOX topping
L-6 Hours and Counting
TimeActivity
L-6H – L-5H 15M ICPS LOX fast fill
L-5H 40M – terminal Core stage LOX replenish
L-5H 40M Stage pad rescue; closeout crew assemble
L-5H 15M – L-5H ICPS LOX vent and relief test
L-5H – L-4H 40M ICPS LOX topping
L-4H 40M – terminal ICPS LOX replenish; all stages replenish
L-4H 40M Built-in hold: 40 minutes
L-4H 40M – L-4H 25M Closeout crew to white room
L-4H 30M – L-4H 20M Crew Module hatch preps and closure
L-4H 20M – L-3H 20M Counterbalance mechanism hatch seal/press decay checks
L-3H 20M – L-2H 40M Crew Module hatch service panel install/closeouts
L-2H 40M – L-2H 20M Launch Abort System (LAS) hatch closure for flight
L-1H 45M – L-1H 40M Closeout crew departs Launch Complex 39B
L-1H 10M Launch Director brief – Flight vehicle/TPS scan results with CICE
L-40 Minutes and Holding
TimeActivity
L-40M Built-in hold: 30 minutes
L-25 Minutes and Holding
TimeActivity
L-25M Transition team to Orion-to-Earth comm loop following final NTD briefing
L-16M Launch Director polls team for “Go” for launch
T-10 Minutes – Terminal Count
TimeActivity
T-10M Ground Launch Sequencer (GLS) initiates terminal count
T-8M Crew Access Arm retract
T-6M GLS go for core stage tank pressurization; Orion set to internal power
T-5M 57S Core stage LH2 terminate replenish
T-4M GLS go for core stage APU start; APU starts; Core stage LOX terminate replenish
T-3M 30S ICPS LOX terminate replenish
T-3M 10S GLS go for purge sequence 4
T-2M 02S ICPS switches to internal battery power
T-2M Booster switches to internal battery power
T-1M 30S Core stage switches to internal power; hold for 3-minute certification hold time verification
T-1M 20S ICPS enters terminal countdown mode
T-50S ICPS LH2 terminate replenish
T-33S GLS sends “Go for Automated Launch Sequencer” command; GLS Cutoff/Recycle
Terminal Count Hold Rules:
  • Teams can hold at T-6M for the duration of the launch window (minus 6 minutes) without recycling.
  • Between T-6M and T-1M 30S: holds up to 3 minutes can resume; longer holds recycle to T-10M.
  • After T-1M 30S but before automated sequencer: recycle to T-10M if window permits.
  • After automated sequencer handover: any stop concludes the launch attempt for that day.

Source: Countdown Begins for Artemis II Wet Dress Rehearsal, NASA, January 31, 2026.

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