NASA’s Artemis II mission, currently slated for a launch, is facing familiar hurdles as engineers grapple with recurring hydrogen leaks. The issue surfaced during a recent wet dress rehearsal, a critical pre-launch test involving the full fueling and operation of the Space Launch System (SLS) rocket. While the rehearsal was more successful than previous tests for the Artemis I mission, the reappearance of the leak raises questions about the long-term viability of the SLS program and the challenges of working with cryogenic fuels.
During the wet dress rehearsal, a hydrogen leak was detected in one of the tail service mast umbilicals – 35-foot structures that provide cryogenic propellant and electrical connections to the SLS core stage. This prompted engineers to terminate the test at the T-5:15 minute mark. Notably, a similar umbilical was the source of hydrogen leaks that plagued the Artemis I mission back in , leading to significant delays and a cancelled launch attempt.
A Persistent Problem
NASA technicians have since replaced two seals within the tail service masts, believing this to be the source of the leak. However, the recurrence of the problem after three years of supposed fixes is concerning. Liquid hydrogen, as NASA acknowledges, is an exceptionally difficult fuel to manage. Being the smallest molecule, it readily escapes through even microscopic gaps in seals and joints. Its extremely low temperature – ( ) – can cause hardware to become brittle and prone to cracking.
Despite these challenges, liquid hydrogen remains crucial for spaceflight due to its unmatched energy-to-weight efficiency, delivering more thrust per pound than any other fuel currently available. NASA has relied on it since the Space Shuttle era, and leaks have been a recurring issue throughout that history. The SLS, being modeled after the Space Shuttle, isn’t surprisingly experiencing similar problems.
The relative infancy of the SLS program also contributes to the ongoing issues. Artemis I represented the rocket’s first and only launch to date. Fewer launches translate to fewer opportunities to identify and resolve these kinds of “kinks” in the system. As Lori Glaze, NASA’s Exploration Systems Development Mission Directorate acting associate administrator, stated after the wet dress rehearsal, “We really did learn a lot from the Artemis 1 mission, and we implemented a lot of the lessons learned yesterday through wet dress.”
Lessons Learned, and a Smoother Path Forward?
The Artemis I experience serves as a stark reminder of the complexities involved. After the initial wet dress rehearsal for Artemis I was scrubbed due to a mobile launcher pressurization issue, it took four subsequent attempts – followed by three launch attempts – to finally get the mission underway. NASA is acutely aware of the need to avoid a similarly protracted timeline for Artemis II.
Currently, engineers are analyzing the removed seals to pinpoint the root cause of the leak. Simultaneously, they are reconnecting the interfaces – the plates and quick-disconnect connections between the rocket and the mobile launcher that carry fuel lines and electrical cables – and conducting tests to validate their repair work before proceeding with the next wet dress rehearsal.
The success of Artemis II is particularly critical as it will be the first crewed flight of the SLS. This mission represents a vital test for the entire program. The agency is hoping that the lessons gleaned from Artemis I have been effectively implemented, and that the current repairs will provide a more lasting solution.
The path forward isn’t without precedent. NASA has dealt with hydrogen leaks for decades, and while the challenges are significant, they are not insurmountable. The current focus on root cause analysis and meticulous testing suggests a more deliberate and systematic approach than was perhaps evident during the initial Artemis I struggles. However, the continued presence of this issue underscores the inherent difficulties of working with such a demanding fuel and the need for ongoing vigilance as the Artemis program progresses.
If NASA can successfully address the hydrogen leaks, the launch date for Artemis II remains within reach. The mission’s success is not only crucial for the future of lunar exploration but also for demonstrating the reliability and sustainability of the SLS program itself.
