WASHINGTON — NASA officials defended their preparations for the Artemis 2 mission after a fueling test experienced the same type of hydrogen leaks that bedeviled Artemis 1 more than three years ago.
NASA wrapped up the wet dress rehearsal, or WDR, for Artemis 2 in the early morning hours Feb. 3 after a hydrogen leak was detected during the terminal phase of the practice countdown. The agency announced shortly afterward that it would not attempt to launch the mission, the first crewed flight to the vicinity of the moon in more than 50 years, during the current launch period, which closes Feb. 11.
The leak during the terminal countdown was the second encountered during the WDR. The first occurred hours earlier during the “fast fill” of the liquid hydrogen tank in the core stage of the Space Launch System. Engineers were able to resolve that leak and resume fueling.
The earlier leak “was similar, I would say, to some of the signatures that we had seen in Artemis 1,” said Charlie Blackwell-Thompson, Artemis launch director, during a Feb. 3 briefing.
Engineers stopped loading liquid hydrogen and allowed seals in a quick-disconnect fitting, part of the interface between ground equipment and the vehicle, to warm up, a technique developed during Artemis 1. After a couple attempts, she said, that approach resolved the leak.
The second leak occurred as the core stage tanks were pressurized. “It went up very quickly, and so we know we had something there we didn’t understand,” Blackwell-Thompson said, adding that it was too early to determine the source. “We really need to get into the plate and take a look.”
Hydrogen leaks are nothing new to the SLS. During the Artemis 1 campaign in 2022, multiple leaks occurred during wet dress rehearsals and two scrubbed launch attempts. At a Jan. 16 briefing, NASA officials said they had made changes to both hardware and procedures based on Artemis 1 to prevent similar problems.
“Why do we think we’ll be successful in Artemis 2? It’s the lessons that we learned,” Blackwell-Thompson said at that briefing. “Artemis 1 was a test flight, and we learned a lot in that campaign getting to launch.”
The recurrence of leaks during the Artemis 2 WDR prompted questions about whether NASA conducted sufficient testing after Artemis 1. John Honeycutt, chair of the Artemis 2 Mission Management Team, said NASA performed extensive component-level testing of systems such as the liquid hydrogen interfaces, understanding how they are affected by imperfections or foreign object debris.
However, he noted there are limits to how much testing can be done at the component level versus testing the fully integrated vehicle and ground systems. “This one caught us off guard,” he said of the leaks during the WDR. “We either had some sort of misalignment or some sort of deformation or debris on the seal.”
One potential factor is the environment experienced by the vehicle during rollout from the Vehicle Assembly Building to Launch Complex 39B. “That rollout environment is very complicated,” said NASA Associate Administrator Amit Kshatriya. “It’s pretty complicated from a stress and strain standpoint.”
Another contributing factor may be the low flight rate of the SLS. Artemis 2 will be just the second launch of the vehicle and the first since November 2022. “The flight rate is the lowest of any NASA-designed vehicle, and that should be a topic of discussion,” NASA Administrator Jared Isaacman said in a Feb. 3 social media post. He said that while the SLS remains the “fastest path” to a human return to the moon, “it is not the most economic path and certainly not the forever path.”
“These are very bespoke components. They’re in many cases made by incredible craftsmen,” Kshatriya said of SLS hardware. “Each one of them is different.”
Path forward
Despite the hydrogen leak issues, NASA officials said the WDR provided valuable data on other aspects of the Space Launch System and the Orion spacecraft. That included the first operational use of a new, larger liquid hydrogen storage tank at the pad and tests of closing Orion’s hatches.
“There’s limited opportunities to do that with the integrated vehicle,” Blackwell-Thompson said of the Orion hatch-closing test, particularly with the rocket loaded with cryogenic propellants. While no individual step in the process is especially complex, she said, “there’s just a timeline and a waterfall of work.”
NASA plans to conduct a second wet dress rehearsal to test fixes for the hydrogen leaks and to complete the final stages of the countdown that were not reached in the first test. The agency has not yet set a date.
Officials said there are no plans to roll the rocket back to the Vehicle Assembly Building. “Right now, it looks like the work that needs to be done can be done at the pad,” said Lori Glaze, NASA acting associate administrator for exploration systems development.
She added that the vehicle can remain at the pad through the next launch opportunity, which runs from March 6 through March 11. “If we go beyond the March time window, we probably would have to roll back,” she said, to perform tasks such as servicing batteries in the SLS upper stage that cannot be done at the pad.
“All in all, a very successful day for us on many fronts,” Blackwell-Thompson said of the WDR. “On a couple of others, we’ve got some work we’ve got to go do.”
“To me,” Honeycutt said, “the big takeaway was we got the chance for the rocket to talk to us, and it did just that.”
