NASA’s ambitious plans to return humans to the moon have encountered a setback. The Artemis II mission, originally slated to launch as early as , has been delayed to at the earliest due to a hydrogen leak discovered during a critical pre-launch test. The leak was detected during a “wet dress rehearsal” – a full simulation of the launch process, including fueling the rocket – that began on .
The Artemis II mission is designed to send four astronauts on a 10-day journey around the moon, marking the first crewed lunar mission in more than 50 years. The crew includes Commander Reid Wiseman, pilot Victor Glover, mission specialist Christina Koch, and Canadian Space Agency astronaut Jeremy Hansen. They had been in medical quarantine in Houston since to minimize the risk of illness before the launch, but have now been released from quarantine pending a new launch target.
The issue centers around the Space Launch System (SLS) rocket, NASA’s flagship launch vehicle for the Artemis program. During the wet dress rehearsal, over 700,000 gallons (2.65 million liters) of super-cold liquid hydrogen and liquid oxygen were pumped into the rocket’s tanks. While engineers initially resolved a small hydrogen leak that occurred earlier in the process, a subsequent spike in the leak rate prompted a halt to the countdown with approximately five minutes remaining.
This isn’t the first time hydrogen leaks have plagued NASA’s efforts to launch the SLS. Similar issues arose during preparations for the Artemis I mission, an uncrewed test flight that ultimately launched successfully in . According to experts, the challenges with hydrogen stem from its unique properties. As the smallest molecule, hydrogen is prone to escaping through even minute fissures in the rocket’s structure. Its extremely low boiling point – minus 423 degrees Fahrenheit (minus 253 Celsius) – also complicates sealing and maintaining the fuel’s integrity.
NASA Administrator Jared Isaacman acknowledged the challenges, stating, “With more than three years between SLS launches, we fully anticipated encountering challenges. That is precisely why we conduct a wet dress rehearsal. These tests are designed to surface issues before flight and set up launch day with the highest probability of success.”
The wet dress rehearsal also revealed other issues beyond the hydrogen leak, including audio communication dropouts and the need to retorque a recently replaced valve on the Orion crew capsule. Cold weather conditions, described as an “Arctic blast,” initially delayed the start of the rehearsal and also impacted the functionality of some cameras and equipment.
Following the test, NASA is currently reviewing the data collected to determine the root cause of the hydrogen leak and develop a plan for remediation. A second wet dress rehearsal will be scheduled, and a flight-readiness review will be conducted before a firm launch date is set. Potential launch windows in include to and . If the mission doesn’t launch by then, it will be delayed until , with a latest possible launch date of .
The Artemis program represents a significant investment in space exploration, with the ultimate goal of establishing a sustainable human presence on the moon and using it as a stepping stone for future missions to Mars. Artemis II is a crucial step in that process, designed to test the systems and gather data necessary for the Artemis III mission, which aims to land astronauts on the lunar surface in 2028. The Artemis II mission also holds historical significance as it will be the first time NASA sends a woman and a Black man to the moon.
NASA plans to provide an update on the wet dress rehearsal findings during a news conference at 1 p.m. ET on . The event will be livestreamed on NASA’s YouTube channel, which also offers a 24/7 live feed of the Artemis II rocket at the Kennedy Space Center.
