A fresh issue casts doubt on the upcoming moon mission for four astronauts
By Muhammad MubashirPublished On 25 Feb 2026
Efforts to get NASA’s historic moon mission off the ground have stalled once again, as engineers navigate a new issue with the rocket set to propel four astronauts on an unprecedented path.
The agency announced Saturday that it had detected a problem with flow of helium, a gas that’s used to pressurize fuel tanks and clean out propellant lines, in the upper part of the Space Launch System, or SLS, moon rocket. Now, the space agency must roll the rocket back off the launchpad and into the nearby Vehicle Assembly Building, or VAB, for servicing as soon as Wednesday — a move that effectively takes the possibility of a March launch date off the table.
The decision represented an abrupt reversal from Friday, when agency officials — on the heels of a fueling test called a wet dress rehearsal — expressed confidence in the potential for a March 6 liftoff. NASA leaders characterized the test, which concluded Thursday, as a success, saying launch controllers had appeared to solve a series of hydrogen fuel leaks that cropped up during an earlier rehearsal in early February.
The helium problem came as a surprise, arising after NASA had wrapped up the latest wet dress Thursday. And launch controllers still aren’t certain what caused the hangup, though NASA Administrator Jared Isaacman said that in any case the issue must be addressed off the launchpad.
NASA is now targeting no earlier than April to launch the mission, called Artemis II.
“The quick work to begin preparations for rolling the rocket and spacecraft back to the VAB potentially preserves the April launch window, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks,” the space agency said in a Monday blog post.
NASA previously identified April 1, 3, 4, 5, 6 and 30 as potential launch days, though during a news conference last Friday agency officials revealed they were assessing potential dates in May and June as well.
When the mission does take off, it’s slated to carry NASA’s Reid Wiseman, Victor Glover and Christina Koch and Canadian Space Agency astronaut Jeremy Hansen on a 10-day slingshot trip around the moon, marking the first time humans have traveled to deep space since the Apollo program ended in 1972.
One problem subsides — another emerges
There are numerous open questions about the feasibility of an April launch date for the mission.
Are there other issues hiding in the data that engineers haven’t yet uncovered? How long will it take to find and address the helium problem? And will rolling the rocket back and forth aggravate NASA’s notorious hydrogen issues?
NASA officials seemed on Friday to think that they had a handle on the SLS rocket’s hydrogen leaks, a notorious problem that has plagued the Artemis program since pre-launch testing for an uncrewed 2022 test flight called Artemis I. Because hydrogen is the lightest element in the universe, it tends to leak out of anything intended to contain it. And after hydrogen seepage plagued the first wet dress rehearsal for Artemis II in early February, the space agency worked to replace two seals around the rocket’s propellant lines in an attempt to better confine the fuel.
Those efforts had appeared to pay off when NASA moved into the second wet dress rehearsal on Thursday.
Still, NASA said that although it had fixed the hydrogen issue, officials weren’t sure why there was some unexpected moisture near the seals that technicians replaced.
“Where it came from, I’m not entirely sure,” said Artemis launch director Charlie Blackwell-Thompson during the Friday news conference. And she said the hydrogen leaks more broadly were still a bit of a puzzle.
“We didn’t have one thing that we could point to where we said this was absolutely it,” Blackwell-Thompson said of the issue. “We had a number of contributing things, but certainly changing out the seals addressed the problem, because we had absolutely an incredible performance.”
NASA’s Artemis II Space Launch System, or SLS, rocket and Orion spacecraft, secured to the mobile launcher, is seen inside the Vehicle Assembly building on January 16 at NASA’s Kennedy Space Center in Florida.
Joel Kowsky/NASA
Then, the helium problem took mission teams right back to the drawing board. Helium gas wasn’t flowing into the upper rocket. And no one was sure why.
Helium serves an important role. It’s ideal for cleaning fuel lines and pressurizing tanks because it stays gaseous even at the super-cold temperatures of the rocket’s propellants — liquid hydrogen and liquid oxygen — and helium is inert, meaning it won’t cause any volatile chemical reactions.
