With Jackie Wattles, CNN
Attempts to send NASA’s historic mission to the moon failed again after engineers ran into a new problem with the rocket that was supposed to propel the four astronauts on an unprecedented trajectory.
The agency announced Saturday that it had discovered a problem with the flow of helium, a gas used to pressurize fuel tanks and purge propulsion lines, atop the Space Launch System (SLS) lunar rocket. The space agency is now due to remove the rocket from the launch pad and move it to the nearby Vehicle Assembly Building (VAB) for maintenance on Wednesday, ruling out a March launch.
The decision represents a radical change from Friday, when agency officials expressed confidence in a March 6 takeoff after a refueling test called a “wet dress rehearsal.” NASA executives called the test, which ended Thursday, a success, saying launch controllers had apparently fixed a series of hydrogen fuel leaks that occurred during a previous test in early February.
The helium problem was a surprise as it occurred after NASA completed its final decontamination test on Thursday. Launch controllers remain unsure of the cause of the problem, though NASA Administrator Jared Isaacman said the problem should be addressed from the launch pad in any case.
NASA is now aiming to launch a mission called Artemis II as early as April.
“The quick work to begin preparations to move the rocket and spacecraft back to the VAB potentially preserves the April launch window pending the results of data inference, repair efforts, and how the schedule will shape up in the coming days and weeks,” the space agency said in a statement on its website.
NASA has previously identified April 1, 3, 4, 5, 6 and 30 as possible launch dates, although during a news conference last Friday, agency officials indicated they are also evaluating possible dates in May and June.
When the mission launches, NASA’s Reed Wiseman, Victor Glover and Christina Koch and Canadian Space Agency astronaut Jeremy Hansen are scheduled to embark on a 10-day catapult trip around the moon, marking the first human flight into deep space since the end of the Apollo program in 1972.
There are many open questions about the feasibility of launching the mission in April.
Are there other hidden problems in the data that the engineers haven’t discovered yet? How long will it take to find and fix a helium problem? Will rocket propulsion exacerbate NASA’s well-known hydrogen problems?
On Friday, NASA officials appeared to believe that the leak of hydrogen from the SLS rocket was under control, a known problem that has plagued the Artemis program since the tests that led to the launch of an uncrewed test flight in 2022 called Artemis I. Because hydrogen is the lightest element in the universe, it has a tendency to leak out of anything that is supposed to contain it. And after a hydrogen leak derailed Artemis II’s first dress rehearsal in early February, the space agency has been working to replace two seals around the rocket’s propulsion lines to try to better limit the fuel.
Those efforts appeared to pay off as NASA began its second dress rehearsal on Thursday.
However, NASA said that while it had fixed the hydrogen problem, officials did not know why there was unexpected moisture near the seals that experts had replaced.
“I’m not entirely sure where it came from,” Artemis launch director Charlie Blackwell-Thompson said during a press conference on Friday. He added that hydrogen leaks, in general, remain a mystery.
“We didn’t have anything that you could call a final solution,” Blackwell-Thompson said of the problem. “We had a number of factors contributing to this, but replacing the seals definitely solved the problem because we had absolutely incredible performance.”
Then a helium problem sent the mission teams back to the drawing board. Gaseous helium did not enter the upper rocket. And no one knew why.
Helium plays an important role. It is ideal for flushing fuel lines and pressure tanks because it remains gaseous even at the very low temperatures of rocket propellants (liquid hydrogen and liquid oxygen) and is inert, meaning it does not cause volatile chemical reactions.
But the helium problem forced engineers to use a backup method to keep the rocket in a safe configuration, as it helps eliminate explosive cryogenic fuel. As of Monday, NASA had not yet disclosed why the gas suddenly stopped.
NASA Administrator Jared Isaacman said on social media that possible causes of the helium problem included a faulty filter placed between ground equipment and the rocket, a faulty valve in the rocket or a problem with the “quick disconnect umbilical,” a line designed to quickly disconnect from the rocket during liftoff. However, these last two scenarios may be the most likely, as these problems have occurred before. Isaacman noted that the valve caused helium problems ahead of Artemis I’s uncrewed test flight in 2022.
“Regardless of the potential failure, accessing and solving any of these problems is only possible at VAB,” Isaacman said.
However, taxiing the rocket from the launch pad and returning it to the VAB also raises new questions about how the hardware will perform during the 13-kilometer (8-mile) round trip, which takes hours each way.
Those responsible for the launch previously said the rocket’s deployment process may have caused some hydrogen leaks. The slow but grueling launch procedure involves slowly moving the rocket and 1.6 million kilogram spacecraft on a moving platform, which can cause stress and strain on the massive vehicle.
“The launch environment is very challenging,” said Amit Kshatriya, NASA’s deputy administrator, during a Feb. 3 press conference.
Even after the helium issue is resolved, NASA may have to subject the SLS rocket to another test.
In an email Monday, a NASA spokesman said launch managers will review what additional tests may be needed after the rocket returns to the launch pad.
Whether during the next dress rehearsal or on launch day, mission controllers must once again keep hydrogen leaks under control when the recently replaced seals begin to show their characteristic volatility after returning to the launch pad.
If additional issues arise during any of these phases, potential April release periods can also be eliminated. And a delay of several months is not excluded. Notably, in the run-up to the Artemis I mission in 2022, the SLS rocket was lifted off the launch pad three times and finally launched about eight months after its originally scheduled launch.
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