NASA’s return-to-the-Moon plans hit a familiar speed bump this week. During a crucial practice countdown for Artemis II, the mission set to carry astronauts around the Moon, engineers ran into fuel leaks while filling the massive rocket, a problem that has haunted the programme before. The issue surfaced during what NASA calls a “dress rehearsal,” a full-scale test meant to mirror the final hours before launch. This rehearsal is critical because its success will decide whether Artemis II can lift off in February or face another delay. What is Artemis II and why does it matter? Artemis II is NASA’s first crewed mission under the Artemis programme and the first time humans will travel toward the Moon in more than five decades. The mission will send four astronauts, three Americans and one Canadian, on a nearly 10-day journey past the Moon, around its far side, and back to Earth. Unlike later Artemis missions, Artemis II will not land on the Moon or enter lunar orbit. Instead, it will test the spacecraft’s life-support systems, navigation, and overall performance with astronauts onboard. Trouble begins during rocket fuelling NASA began loading the 98-metre-tall Space Launch System (SLS) rocket with super-cold liquid hydrogen and liquid oxygen at Kennedy Space Center around midday. More than 2.6 million litres of fuel needed to be pumped into the rocket and kept there for several hours, just as it would be on launch day.
But only a couple of hours into the process, sensors detected excessive hydrogen building up near the bottom of the rocket. Fuelling had to be paused multiple times, with only about half of the core stage filled. Hydrogen leaks are especially dangerous because the gas is highly flammable and difficult to contain. Also read: First time in six decades, NASA juggles between two missions, US space agency faces rare double countdown
A familiar problem from the past The leaks triggered uncomfortable déjà vu for NASA. Hydrogen leaks repeatedly delayed the agency’s first SLS rocket in 2022 before finally launching without a crew. This time, engineers tried to manage the issue using techniques developed during that earlier mission. Still, the interruption highlighted how challenging it remains to handle the rocket’s complex fuel systems. Astronauts watch from quarantine While engineers worked on the ground, the Artemis II crew followed the test from Houston, about 1,600 kilometres away at NASA’s Johnson Space Center. The astronauts have been in quarantine for more than a week, waiting to see whether the rehearsal succeeds. The outcome will determine when, or if, they can proceed toward launch. Tight launch windows add pressure NASA is already running behind schedule due to an intense cold snap that delayed operations. Countdown clocks started ticking late Saturday night and were designed to stop just 30 seconds before liftoff, right before engine ignition. The agency has very limited launch opportunities. If Artemis II does not launch by February 11, the mission will be postponed until March. Extreme cold has already shortened February’s launch window by two days. Also read: Indian-origin woman behind NASA’s first AI-planned rover drive on Mars
What happens next If the fuelling demonstration can be completed successfully, NASA will move closer to setting a launch date. If not, Artemis II may have to wait, once again, while engineers work to resolve the leaks. NASA last sent astronauts to the Moon during the Apollo missions of the 1960s and 1970s. With Artemis II, the agency hopes to restart human journeys beyond Earth orbit and lay the groundwork for future lunar landings. For now, though, NASA’s path back to the Moon depends on solving a stubborn problem on the launchpad, keeping hydrogen exactly where it belongs.
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