Why NASA still uses leak-prone hydrogen fuel for Artemis moon missions

NASA’s next crewed mission around the moon has faced a familiar challenge — hydrogen fuel leaks — raising questions about why the space agency continues using a propellant known for being difficult to contain.

Engineers recently halted fueling during a critical Artemis II pre-launch test after detecting concerning levels of leaking super-cold liquid hydrogen. Similar issues have delayed previous missions, including the uncrewed Artemis I launch and even rockets from the Space Shuttle era.

So why keep using it?

The answer comes down to performance. Hydrogen is the lightest element in the universe, making it incredibly efficient as rocket fuel. Because it’s so lightweight, engines can produce more thrust with less fuel weight — a key advantage when launching heavy spacecraft and crew beyond Earth’s orbit. In technical terms, hydrogen delivers one of the highest “specific impulse” ratings of any rocket propellant, meaning maximum power for its mass.

But those same properties also make hydrogen hard to control. The tiny molecules can escape through even microscopic gaps, and the fuel must be stored at extremely cold temperatures — about minus 423 degrees Fahrenheit — putting stress on seals and materials that hold it in place.

NASA’s Space Launch System uses hydrogen in both the core and upper stages of the rocket. That design is partly rooted in policy decisions that required the program to reuse technology, workforce and infrastructure from the Space Shuttle era — which also relied on hydrogen.

Engineers say the SLS remains an experimental system still being understood and refined. Each new rocket behaves slightly differently, and researchers continue testing materials, seals and fueling procedures to reduce leaks.

Despite the challenges, NASA officials emphasize hydrogen can be used safely and efficiently — and so far, leaks have not caused accidents.

For now, the fuel’s unmatched performance keeps it central to NASA’s plans to return humans to the moon, even as engineers continue working to make it more manageable.

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