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Following an attempt earlier this month, NASA is now targeting Thursday for the final fueling test and simulated launch countdown of the Artemis 2 mission.
The Artemis 2 Space Launch System (SLS) rocket and Orion spacecraft at NASA’s Kennedy Space Center in Florida on Feb. 1, moments after the countdown began for the mission’s first wet dress rehearsal. Credit: NASA/John Kraus
After issues with a liquid hydrogen leak thwarted an attempt earlier this month, NASA is targeting Thursday, Feb. 19, for a second Artemis 2 wet dress rehearsal tanking day.
Artemis 2 represents humanity’s return to the Moon for the first time in more than 50 years, but it can’t leave the ground until it passes one final hurdle — a wet dress rehearsal.
The upcoming wet dress rehearsal attempt follows several days of testing and repairs. After the initial wet dress rehearsal on Feb. 3, technicians replaced two seals near the “tail service mast umbilical” — the three-story structure that connects fueling lines to the rocket — where the leaking hydrogen was detected.
To verify those fixes, NASA conducted a partial fueling on Feb. 12. While the new seals performed as expected, a separate issue emerged when a filter in the ground-side equipment restricted the flow of liquid hydrogen. Engineers replaced that filter and prepared the systems for this second full-scale rehearsal.
While the primary fueling activities occur on Thursday, the official countdown begins tonight at 6:40 p.m. EST. Launch controllers will arrive at Kennedy Space Center to begin the two-day countdown sequence leading up to a simulated launch time of 8:30 p.m. on Feb. 19.
NASA will not schedule a specific launch date until the results of the second wet dress rehearsal are clear, but the earliest available launch window opens on March 6.
Wet dress rehearsals are the final test before a launch takes place. For Artemis 2, engineers will load the roughly 700,000 gallons of cryogenic liquid fuel into the SLS rocket and simulate a full launch countdown, running through several potential launch scenarios, like holding or recycling the countdown clock. Although the astronauts will not be on board, a specialized ground team will be at the pad to practice the specific steps for sealing the Orion spacecraft’s hatches.
The second attempt will follow much of the same script as the first. The team will attempt two runs through the final ten minutes before launch, a window known as the terminal countdown. They will pause the count at T-1 minute and 30 seconds, hold the countdown for up to three minutes, then resume the countdown before holding it again at T-33 seconds. Then, operators will recycle the countdown back to T-10 minutes and run through the terminal countdown one last time before emptying the fuel tanks and wrapping up the test.
Not only does a wet dress rehearsal allow the team to practice for real-world scenarios that could impede the launch, but they may also have to stop the countdown to troubleshoot any issues that arise in real time.
During the first Artemis 2 wet dress rehearsal, unforeseen issues with leaking liquid hydrogen led to unplanned holds and the eventual termination of the test. While engineers initially managed to troubleshoot the temperamental fuel line by allowing hardware interfaces to warm up and reseat the seals, the leak recurred. A spike in fuel levels recorded at the T-5 minute 15-second mark forced officials to scrub the remainder of the rehearsal before they could demonstrate the planned recycles or transition the rocket to its own internal power. Meeting those incomplete objectives is now a high priority for the upcoming test on Feb. 19.